Java Ninja Chronicles By Norris Shelton

Things I learned in the pursuit of code

I was working on Java some code. It had two different objects that extended a common base object. There was a method that was called to load the common values. The receiving methods would then cast the returned object to the type that it was given. Here was the original code:

private ConvergeBaseRequest setProperties(ConvergeBaseRequest request) {
    // do some stuff
    request.setSslMerchantId(merchantId);
    request.setSsluserId(userId);
    request.setSslPin(pin);
    return request;
}

It was called by:

request = (ConvergeCCSaleRequest) setProperties(request);

After a little tweaking, I came up with the following method:

private <T extends ConvergeBaseRequest> T setProperties(T request) {
    // do some stuff
    request.setSslMerchantId(merchantId);
    request.setSsluserId(userId);
    request.setSslPin(pin);
    return request;
}

This made it simpler to call also,

request = setProperties(request);

With just a little bit of smarts, we were able to use Java Generics to make our calling code a little bit simpler.

July 19th, 2016

Posted In: Java, java ninja, Javaninja

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I like to use SpringMVC for my JSON controllers. I do not prefer to return HTTP status codes other than 200, but sometimes you don’t have a choice. I was working on a project where the service would return the requested resource when it is available. If the resource is not found, then it is supposed to return an HTTP status of 404 with a messages. I thought this would be included right out of the box, but it wasn’t.

What Spring MVC offers and why it didn’t work

With Spring MVC, you have the ability to define an exception and have that exception return a specified HTTP status code when it reaches the controllers. Here is what an exception class would look like:

package com.twinspires.brisdataapi.bdsserver.exceptions;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ResponseStatus;

/**
 * @author norris.shelton
 */
@ResponseStatus(value = HttpStatus.NOT_FOUND)
public class NotFoundException  extends RuntimeException {
    /**
     * Constructs a new runtime exception with the specified detail message.
     * The cause is not initialized, and may subsequently be initialized by a
     * call to {@link #initCause}.
     * @param message the detail message. The detail message is saved for later retrieval by the {@link #getMessage()}
     *                method.
     */
    public NotFoundException(String message) {
        super(message);
    }
}

This does provide a way to specify a message, but it doesn’t get displayed when a message is returned by the controllers. Ugh.

This would provide a good start, but I would need an exception handler to get the message. Unfortunately, all of the examples of the exception handlers show a method per exception.

Doing the least to make it work

This details the changes that I needed to make to allow the service to function correctly. I wanted to create as few classes as possible.

Define an exception

I created an exception that extends RuntimeException. I didn’t add a @ResponseStatus because I didn’t want to have to make an exception for each status code. I created a constructor that takes an HTTP status code and a message. This allows me to have one exception that I can reuse in all of my controllers and always return the correct status and message.

package com.twinspires.brisdataapi.bdsserver.exceptions;

import org.springframework.http.HttpStatus;

/**
 * @author norris.shelton
 */
@SuppressWarnings("ClassWithoutNoArgConstructor")
public class BdsServiceException extends RuntimeException {

    private HttpStatus httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;

    public HttpStatus getHttpStatus() {
        return httpStatus;
    }

    /**
     * Constructs a new runtime exception with the specified detail message.
     * The cause is not initialized, and may subsequently be initialized by a
     * call to {@link #initCause}.
     * @param message the detail message. The detail message is saved for later retrieval by the {@link #getMessage()}
     *                method.
     */
    public BdsServiceException(HttpStatus httpStatus, String message) {
        super(message);
        this.httpStatus = httpStatus;
    }
}

Define SpringMVC exception handler

Now that I have an exception that has all of the information that I want returned to the caller of my service, I need to define an exception handler. It is the same type of exception handler that you normally see, except it returns a ResponseEntity. With the ResponseEntity, I can return the retrieve the correct status code and message from the exception and return them to the caller.

package com.twinspires.brisdataapi.bdsserver.spring;

import com.twinspires.brisdataapi.bdsserver.exceptions.BdsServiceException;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
public class ExceptionHandlerAdvice { 
 
    @ExceptionHandler(BdsServiceException.class)
    public ResponseEntity handleException(BdsServiceException e) {
        // log exception 
        return ResponseEntity.status(e.getHttpStatus()).body(e.getMessage());
    }         
} 

Putting it to use

All that is left is throwing the exception. I threw the exception with the desired HTTP status code and the message.

            throw new ResourceException(HttpStatus.NOT_FOUND, "We were unable to find the specified resource.");

June 22nd, 2016

Posted In: Java, java ninja, Javaninja, Spring, Spring MVC

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We were using FasterXML on the same object to generate JSON and XML. Unfortunately, the object itself didn’t define the desired markup. It used JAXB annotations to add a wrapper around a set of data.

XML and JSON output based upon class definition

The class had the following property defined:

public List<TestRacingEventResponse> getRacingEvents() { return _racingEvents; }
public void setRacingEvents(List<TestRacingEventResponse> racingEvents) { this._racingEvents = racingEvents; }

This would generate XML like:

<racingEvents>
    <....>
</racingEvents>
<racingEvents>
    <....>
</racingEvents>
<racingEvents>
    <....>
</racingEvents>

The JSON would be outputted like this:

{racingEvents
{…}
}
{racingEvents
{…}
}
{racingEvents
{…}
}

JAXB to create a wrapper and redefine the element

This isn’t what was wanted. The desired output was a racingEvents container around a list of racingEvent containers. This is quite easy in XML via JAXB. The declaration with the required JAXB is as follows:

@XmlElementWrapper(name="racingEvents")
@XmlElement(name="racingEvent")
public List<TestRacingEventResponse> getRacingEvents() { return _racingEvents; }
public void setRacingEvents(List<TestRacingEventResponse> racingEvents) { this._racingEvents = racingEvents; }

This would generate XML like:

<racingEvents>
    <racingEvent>
        <....>
    </racingEvent
    <racingEvent>
        <....>
    </racingEvent
    <racingEvent>
        <....>
    </racingEvent
</racingEvents>

This works great for XML, but JSON doesn’t honor JAXB annotations. This leaves us with two alternatives. Create a class structure that mimics the structures you wanted. That would be creating a RacingEvents property in our enclosing class that is a List, then create a RacingEvent object that has the required fields.

Configure FasterXML (Jackson 2) to honor JAXB Wrapper annotation

Another way to do this is to instruct the JSON marshaller to honor the JAXB annotations. We are using Jackson 2 (FasterXML). In our particular case, we were using CXF for the front-end services. The original XML configuration is as follows:

<jaxrs:server id="hptsWebService" address="/">
    <jaxrs:serviceBeans>
        <bean id="accountServices" class="com.twinspires.hpts.servicedefinitions.AccountServices"/>
        <bean id="racingContentServices" class="com.twinspires.hpts.servicedefinitions.RacingContentServices"/>
        <bean id="systemInfoServices" class="com.twinspires.hpts.servicedefinitions.SystemInfoServices"/>
        <bean id="testerServices" class="com.twinspires.hpts.servicedefinitions.TesterServices"/>
    </jaxrs:serviceBeans>
    <jaxrs:providers>
        <bean class="com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider"/>
    </jaxrs:providers>
</jaxrs:server>

I needed to be able to configure the ObjectMapper. Unfortunately, I couldn’t get to the ObjectMapper in the code because the JacksonJaxbJsonProvider only exposed a MAPPER. That seems like a bug to me. To get around this, I declared the JacksonJaxbJsonProvider separately.

<bean id="jacksonJaxbJsonProvider" class="com.fasterxml.jackson.jaxrs.json.JacksonJaxbJsonProvider"/>

<jaxrs:server id="hptsWebService" address="/">
    <jaxrs:serviceBeans>
        <bean id="accountServices" class="com.twinspires.hpts.servicedefinitions.AccountServices"/>
        <bean id="racingContentServices" class="com.twinspires.hpts.servicedefinitions.RacingContentServices"/>
        <bean id="systemInfoServices" class="com.twinspires.hpts.servicedefinitions.SystemInfoServices"/>
        <bean id="testerServices" class="com.twinspires.hpts.servicedefinitions.TesterServices"/>
    </jaxrs:serviceBeans>
    <jaxrs:providers>
        <ref bean="jacksonJaxbJsonProvider"/>
    </jaxrs:providers>
</jaxrs:server>

Now that the object is separate, I had to find a place where I could manipulate it. I found an object that was related to the functionality that I needed and added a constructor that took the JacksonJaxbJsonProvider as input. Once I had that object, I could configure to my heart’s content.

My modifications involved creating a new OjbectMapper. I preferred to get the ObjectMapper that was being used, but there was no getter. Once I have the ObjectMapper, I set a property that indicates that I want use the XmlElementWrapper as a wrapper for my output.

    @Autowired
    public HttpUtil(JacksonJaxbJsonProvider jacksonJaxbJsonProvider) {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.enable(MapperFeature.USE_WRAPPER_NAME_AS_PROPERTY_NAME);
        jacksonJaxbJsonProvider.setMapper(objectMapper);
    }

Now that we have told the JSON marshaller to honor the JAXB wrapper annotation, output should be:

{racingEvents
    {races
        {...}
    }
    {races
        {...}
    }
    {races
        {...}
    }
}

Conclusion

To have a FasterXML honor JAXB annotations when it outputs JSON, you have to instantiate the JacksonJaxbJsonProvider separately so it can be injected. Once it is injected in code, you can create and configure an ObjectMapper.

June 10th, 2016

Posted In: FasterXML, Jackson 2, Java, java ninja, Javaninja, JAXB, json

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Accessing properties via Spring is very easy. To read a properties file is very easy. This reads the given properties file from the file system and places the values in a map named rabbitConfiguration. It takes advantage of SpEl to get a system property and use that to resolve the file name.

<util:properties id="rabbitConfiguration" location="file:#{systemProperties.APP_CONFIG}/funding.properties"/>

My problems started when I tried to use the values from the properties file that contained periods. I tried to use them like:

    <bean id="rabbitConnectionFactory" class="org.springframework.amqp.rabbit.connection.CachingConnectionFactory"
          c:hostname="#{rabbitConfiguration.vipre.host}"
          c:port="#{rabbitConfiguration.vipre.port}"
          p:username="#{rabbitConfiguration.vipre.user}"
          p:password="#{rabbitConfiguration.vipre.password}"/>

Spring did not like it. It thought that vipre was my property and host was something to be accessed off of it like an object. This is the exception that was thrown.

Caused by: org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 20): Property or field 'vipre' cannot be found on object of type 'java.util.Properties' - maybe not public?
	at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:164)
	at org.springframework.beans.factory.support.AbstractBeanFactory.evaluateBeanDefinitionString(AbstractBeanFactory.java:1365)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.doEvaluate(BeanDefinitionValueResolver.java:255)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.evaluate(BeanDefinitionValueResolver.java:228)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:204)
	at org.springframework.beans.factory.support.ConstructorResolver.resolveConstructorArguments(ConstructorResolver.java:648)
	at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:140)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1137)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1040)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351)
	... 109 common frames omitted
Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 20): Property or field 'vipre' cannot be found on object of type 'java.util.Properties' - maybe not public?
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:224)
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:94)
	at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:81)
	at org.springframework.expression.spel.ast.CompoundExpression.getValueRef(CompoundExpression.java:57)
	at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:87)
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:120)
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:242)
	at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:161)
	... 124 common frames omitted

I searched and searched around the internet trying to find a way to work around. I tried single-quotes, back-slashes, double-quotes, double-quotes and single-quotes together. Nothing seemed to work, then it hit me. To get around this, I approached the properties access via the array/bracket syntax (#{rabbitConfiguration[‘vipre.port’]}

    <bean id="rabbitConnectionFactory" class="org.springframework.amqp.rabbit.connection.CachingConnectionFactory"
          c:hostname="#{rabbitConfiguration['vipre.host']}"
          c:port="#{rabbitConfiguration['vipre.port']}"
          p:username="#{rabbitConfiguration['vipre.user']}"
          p:password="#{rabbitConfiguration['vipre.password']}"/>

May 31st, 2016

Posted In: Java, java ninja, Javaninja, SpEl, Spring

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Spring provides the SimpleNamingContextBuilder to handle cases where the code that is tested needs a JNDI environment entry.

Steps to using a Spring SimpleNamingContextBuilder

Using the Spring SimpleNamingContextBuilder is fairly easy. There are basically three steps:

  1. Instantiate the variable
  2. Bind objects to their JNDI keys in the context builder (repeat as necessary)
  3. Activate the context builder

Full Example Utility

In my case, I only had to bind one thing, the full path to a file.

Here is the utility class that I built to hold the code.

package com.twinspires.cam;

import org.springframework.mock.jndi.SimpleNamingContextBuilder;

import javax.naming.NamingException;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.file.Path;
import java.nio.file.Paths;

import static org.junit.Assert.fail;

/**
 * @author norris.shelton
 */
public class JunitTestUtility {

    /**
     * Performs environmental setup for Cam tests.
     * @throws NamingException if unable to activate the builder
     * @throws URISyntaxException if unable to find the properties file by a classloader
     */
    public static void setup() throws NamingException, URISyntaxException {
            String camPropertiesFile = "cam-test.properties";
        URL url = JunitTestUtility.class.getClassLoader().getResource(camPropertiesFile);
        if (url != null) {
            Path path = Paths.get(url.toURI());
            if (path != null) {
                SimpleNamingContextBuilder builder = new SimpleNamingContextBuilder();
                builder.bind("cam.config.path", path.toString());
                builder.activate();
            }
        } else {
            fail("Unable to find cam-test.properties in src/test/resources");
        }
    }
}

How to reuse in a Junit test class

Once that is done, it is quite easy to reuse it. In my case, all of the test classes for a project needed that.

    @BeforeClass
    public static void setup() throws Exception {
        JunitTestUtility.setup();
    }

May 24th, 2016

Posted In: Java, java ninja, Javaninja, JUnit, Spring, TDD

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Get JMeter

Download the software from Apache from http://jmeter.apache.org/download_jmeter.cgi. I use IntelliJ. It says to define a JMETER_HOME environment variable. Once you have that, you should be able to create JMeter file times (*.jmx). If you right-click on a *.jmx file, IntelliJ will give you the option to run the file. Running the file will open the JMeter application with the specified file.

Test Plan

The test plan is the first item in the left-hand panel. It looks like a Erlenmeyer flask. This is where you will put the name of your test.

You can create User Defined Variables that can be used in other places in the test. An example a user defined variable with the name host and a value of localhost. It can be used by ${host}. Then later, the value can be changed to test to another server.

Thread Group

You can add a Thread Group by right-clicking on the Test Plan and selecting Threads (Users), then Thread Group. It looks like a spool of thread. The thread group is used to control the load. What should happen if there is a sampler error? Continue and Stop Thread are common options.

There is a Thread Properties box that has most of the options here. You can control how many threads (users) you have, how long it takes to ramp up a thread. One second is the default. You can also specify how many iterations (Loop Count) you should perform.

There is also a Scheduler checkbox. If you select that, then there will be a Scheduler Configuration that will become visible. That is good when you want the test to run for a specified amount of time, instead of iterations. You don’t have to specify the Start Time or the End Time. All you need to specify is the Duration (seconds>. If you want a test to run 5 minutes, specify 300 seconds.

HTTP Request

You can add an HTTP Request by right-clicking on the Thread Group, selecting Add, Sampler, then selecting HTTP Request. It looks like a dropper. The http request is where you can specify and control the http request. Some of the things you can specify:

  • server Name or IP. I would use a User Defined Variable here (e.g. ${host}).
  • port
  • connection and response timeouts
  • protocol (defaults to http)
  • HTTP method (defaults to GET)
  • path
  • URL parameters
  • post body data

Once you have something that can generate results, there are several different ways to be presented the data.

View Results Tree

You can add a View Results Graph by right clicking the HTTP Request, then selecting Add, then Listener, then View Results Tree. The icon looks like a dial meter. The View Results Tree is very helpful in debugging your test. It shows each request and each response. There is also the ability to format the response by type, for example JSON.

One caveat with this is that if you have a very long running test or a lot of data, your JMeter will run out of memory. To counter this, you can have it write the data to a file. I usually just disable the View Results Tree by right-clicking on it and clicking disable.

View Results in Table

You can add a View Results in Table by right clicking the HTTP Request, then selecting Add, then Listener, then View Results in Table. The icon looks like a dial meter. The View Results in Table shows the results in tabular format. It has timing information.

Sample #  Start Time	Thread Name       Label         Sample Time(ms)  Status   Bytes  Latency  Connect Time(ms)
19        08:56:26.194  Thread Group 1-1  HTTP Request  9                Success  383    8        2

This is usually the panel I have open when I am running a test. The panel bottom line shows the average and the standard deviation. You can write the results to a file.

Response Time Graph

You can add a Response Time Graph by right clicking the HTTP Request, then selecting Add, then Listener, then Response Time Graph. The icon looks like a dial meter. The Response Time Graph shows the results in in a graphical format. Typically time horizontally and milliseconds vertically. This can also be written to a file.

Summary Report

You can add a Summary Report by right clicking the HTTP Request, then selecting Add, then Listener, then Summary Report. The icon looks like a dial meter. The Summary Report outputs timing information for each JMeter Sampler (e.g. HttpRequest).

Label         # Samples  Average  Min  Max  Std. Dev.          Error %  Throughput         KB/sec              Avg. Bytes
HTTP Request  45619      22       17   115  6.598780184509035  0.0      387.7254415339373  211.72920469177618  559.1861724281549
TOTAL         45619      22       17   115  6.598780184509035  0.0      387.7254415339373  211.72920469177618  559.1861724281549

Generate Summary Results

You can add a Generate Summary Results by right clicking the HTTP Request, then selecting Add, then Listener, then Generate Summary Results. The icon looks like a dial meter. The Generate Summary Results outputs a summarized timing data to the console. The output is below. Notice that every other line is a summary to that point and the others are deltas.

Generate Summary Results +   3265 in     9s =  366.9/s Avg:    22 Min:    17 Max:   110 Err:     0 (0.00%) Active: 10 Started: 10 Finished: 0
Generate Summary Results +  13024 in    30s =  434.1/s Avg:    22 Min:    17 Max:   110 Err:     0 (0.00%) Active: 10 Started: 10 Finished: 0
Generate Summary Results =  16289 in    39s =  418.7/s Avg:    22 Min:    17 Max:   110 Err:     0 (0.00%)
Generate Summary Results +  11524 in    30s =  384.2/s Avg:    21 Min:    17 Max:   112 Err:     0 (0.00%) Active: 10 Started: 10 Finished: 0
Generate Summary Results =  27813 in    69s =  403.7/s Avg:    22 Min:    17 Max:   112 Err:     0 (0.00%)
Generate Summary Results +  12283 in    30s =  409.4/s Avg:    22 Min:    17 Max:   115 Err:     0 (0.00%) Active: 10 Started: 10 Finished: 0
Generate Summary Results =  40096 in    99s =  405.4/s Avg:    22 Min:    17 Max:   115 Err:     0 (0.00%)
Generate Summary Results +    411 in   1.3s =  324.6/s Avg:    20 Min:    17 Max:    26 Err:     0 (0.00%) Active: 0 Started: 10 Finished: 10
Generate Summary Results =  40507 in 100.2s =  404.4/s Avg:    22 Min:    17 Max:   115 Err:     0 (0.00%)

CSV Data Set Config

Needing to run a data-driven test is very common. How do you get JMeter to use data in it’s tests? Use a CSV, of course. You can add a CSV Data Set Config by right clicking the Thread Group, then selecting Add, then Config Element, then CSV Data Set Config. The icon looks like test tubes in a test tube rack. The CSV Data Set Config has the following fields:

  • Filename – the name of the file containing the data
  • File Encoding – file encoding (optional)
  • Variable names (comma-delimited) – the names of the data fields, in order. These names will be available like User Defined Variables (e.g. id -> ${id}, according to the Sharing Mode described below.
  • Delimeter – “,” or “\t” for tab, etc. or use specified value
  • Allow quoted data? – true or false or use specified value
  • Recycle on EOF ? – true or false or use specified value
  • Stop thread on EOF ? – true or false or use specified value
  • Sharing mode – All threads, current thread group, current thread or use specified value

Once you have this configured, you can use the exposed CSV data just as a User Defined Variable that changes per entry in HTTP Requests, etc. Then you can substitute the value in the Path as a URL parameter or path parameter. You can also use them in the body of the post, etc.

HTTP Header Manager

HTTP Header Manager can be used to inject headers to indicate the Content-Type, Accept, etc. You can add a CSV HTTP Header Manager by right clicking the HTTP Request, then selecting Add, then Config Element, then HTTP Header Manager.

HTTP Authorization Manager

HTTP Authorization Manager can be used to inject authorization header information into a request. You can add a HTTP Authorization Manager by right clicking the HTTP Request, then selecting Add, then Config Element, then HTTP Authorization Manager.
The following fields are available:

  • Base URL – URLs to send the authorization header
  • Username – the username to authorize
  • Password – the unencrypted password value
  • Domain – The domain to use for NTLM
  • Realm – The realm to use for NTLM
  • Mechanism – Type of authorization to perform. This depends on the Sampler Mechanism that is specified on HTTP Request in the Implementation field.

Most of the marshalling I have to do it done by Spring. However, I sometimes have to do this manually. Let’s see how easy it is with Jackson 2 (FasterXML).

Maven dependency

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.4.3</version>
</dependency>

Import the ObjectMapper

The ObjectMapper is the object that you will instantiate and use for all conversions.

import com.fasterxml.jackson.databind.ObjectMapper;

Object to String

Given an object, it is pretty easy to use an ObjectMapper.

ObjectMapper objectMapper = new ObjectMapper();
String myString = objectMapper.writeValueAsString(myObject);

String to Object

If you have a JSON string and need to convert that to an object, you also use the ObjectMapper.

ObjectMapper objectMapper = new ObjectMapper();
MyObject myObject = objectMapper.readValue(myJsonString, MyObject.class);

May 12th, 2016

Posted In: FasterXML, Java, java ninja, Javaninja, json

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Creating a thread pool within a web application is usually frowned upon. Why is that?

  • If you create your thread pool within the web application context, your pool will be competing for threads with your web application.
  • Another problem with creating your thread pool within the web application context is that you don’t know what assumptions the web container makes about what is available in the thread. It could be storing information related to security, etc on the thread.
  • Another problem with creating threads within the web application context is that those threads will respond to the web application shutdown. This may be counter to what you want to happen. Those threads may need to run to completion, regardless of the desire to shutdown the web application context.

Creating our Spring thread worker

Now that we know what not to do and why, let’s start with the right way to do this. The first thing is that we need to implement a bean to perform our work. There a couple of things that will need to be different from other generic beans.

  • The beans should be scope Prototype. Spring beans default to Singleton scope. That means that there is one bean per Spring container. When you are making worker threads, they should be scoped as prototype. That means that a new bean is created whenever one is requested.
  • The class should implement the Runnable interface. This dictates that a run method must be implemented. This method is called when the thread is started as a separately executing thread.

Here is an example thread worker. It is scoped Prototype and implements Runnable. It doesn’t do much, but waits a random amount of time to simulate asynchronous work. I added a field with a custom value and a little logging so we can see the workings of the threads via the logs.

package com.javaninja.spring.webmvc.threads;

import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

import java.util.LinkedList;
import java.util.List;
import java.util.Random;
import java.util.UUID;

/**
 * This class performs the work that is needed in the thread pool.
 * @author norris.shelton
 */
@Component
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class ThreadWorker implements Runnable {

    private Logger logger = LoggerFactory.getLogger(getClass());

    private String uniqueInfo;

    private List<String> data = new LinkedList<>();


    public void setUniqueInfo(String uniqueInfo) {
        this.uniqueInfo = uniqueInfo;
    }

    public List<String> getData() {
        return data;
    }


    /**
     * When an object implementing interface {@code Runnable} is used to create a thread, starting the thread
     * causes the object's {@code run} method to be called in that separately executing thread.
     * <p>
     * The general contract of the method {@code run} is that it may take any action whatsoever.
     * @see Thread#run()
     */
    @Override
    public void run() {
        logger.info("Started runner {}", uniqueInfo);

        try {
            int milliseconds = new Random().nextInt(10000);
            logger.info("{} sleeping for {} ms", uniqueInfo, milliseconds);
            Thread.sleep(milliseconds);
        } catch (InterruptedException e) {
            logger.error("Trouble with thread", e);
        }

        // simulating having results
        for (int i = 0; i < 5; i++) {
            data.add(UUID.randomUUID().toString());
        }

        logger.info("Runner {} finishing data={}", uniqueInfo, data);
    }

    /**
     * Returns a string representation of the object. In general, the {@code toString} method returns a string that
     * "textually represents" this object. The result should be a concise but informative representation that is easy
     * for a person to read. It is recommended that all subclasses override this method.
     * <p>
     * The {@code toString} method for class {@code Object} returns a string consisting of the name of the class of
     * which the object is an instance, the at-sign character `{@code @}', and the unsigned hexadecimal representation
     * of the hash code of the object. In other words, this method returns a string equal to the value of: <blockquote>
     * <pre>
     * getClass().getName() + '@' + Integer.toHexString(hashCode())
     * </pre> </blockquote>
     * @return a string representation of the object.
     */
    @Override
    public String toString() {
        return ReflectionToStringBuilder.toString(this);
    }
}

Defining our Spring thread pool

Spring provides the ThreadPoolTaskExecutor class that takes out most of the difficulty. It provides some customization that proves to be extremely useful. Some of the settings are below:

  • corePoolSize – This is minimum pool size. The default value is 1.
  • maxPoolSize – This is the maximum pool size. the default is Integer.MAX_VALUE.
  • waitForTasksToCompleteOnShutdown – Should the pool wait for tasks to complete when the Spring container is shutdown. The default value is false.
  • awaitTerminationSeconds – How long should the Spring container wait for the pool to finish its tasks when the Spring container is told to shut down.

An example is below:

<bean id="taskExecutor" class="org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor"
          p:corePoolSize="5"
          p:maxPoolSize="5"
          p:waitForTasksToCompleteOnShutdown="true"
          p:awaitTerminationSeconds="20"/>

Using a pool with fixed workers

Our first example will have a fixed number of worker threads. This is the simplest way to do it if you know you will always have a specific number of thread workers. The first thing to do to use the pool is get a reference to the TaskExecutor. Then inject the number of workers that we will need. Remember that these workers are all scoped Prototype to ensure that each can work completely independent of each other. I set a unique value into each thread worker and have each one of them sleep a random amount of time to help identify it while it is working. To start a worker we call the execute method on the thread pool with our worker as the method parameter.

package com.javaninja.spring.webmvc.threads;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.stereotype.Service;

import java.util.UUID;

/**
 * This is the code that controls the execution of a fixed number of worker threads.
 * @author norris.shelton
 */
@Service
public class FixedThreadService {

    private Logger logger = LoggerFactory.getLogger(getClass());

    @Autowired
    private ThreadPoolTaskExecutor taskExecutor;

    @Autowired
    private ThreadWorker worker1;

    @Autowired
    private ThreadWorker worker2;

    @Autowired
    private ThreadWorker worker3;

    @Autowired
    private ThreadWorker worker4;

    @Autowired
    private ThreadWorker worker5;

    public String withFixedThreads() {
        worker1.setUniqueInfo("1");
        taskExecutor.execute(worker1);

        worker2.setUniqueInfo("2");
        taskExecutor.execute(worker2);

        worker3.setUniqueInfo("3");
        taskExecutor.execute(worker3);

        worker4.setUniqueInfo("4");
        taskExecutor.execute(worker4);

        worker5.setUniqueInfo("5");
        taskExecutor.execute(worker5);

        return UUID.randomUUID().toString();
    }
}

Using a pool with dynamic workers

Sometimes we don’t know how many worker threads we will need until runtime. This requires a slightly different solution. We will need access to the Spring context to create as many workers as needed. Remember that the thread worker classes are scoped as Prototype. This means that each time we request a bean via getBean, that we are getting a totally new bean that will execute completely independent of any other thread worker bean. From there, the code is similar and will actually be shorter.

NOTE: to get the Spring context during the execution of the bean, you should implement ApplicationContextAware. This dictates that you have a setApplicationContext method. Once you have the context injected, you can use it however you need. To inject beans on demand, in our case.

package com.javaninja.spring.webmvc.threads;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ApplicationContextException;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.context.MessageSourceAware;
import org.springframework.context.ResourceLoaderAware;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
import org.springframework.stereotype.Service;

import java.util.UUID;

/**
 * This is the code that controls the execution of a dynamic number of worker threads.
 * @author norris.shelton
 */
@Service
public class DynamicThreadService implements ApplicationContextAware {

    private ApplicationContext applicationContext;

    private Logger logger = LoggerFactory.getLogger(getClass());

    @Autowired
    private ThreadPoolTaskExecutor taskExecutor;

    /**
     * Set the ApplicationContext that this object runs in. Normally this call will be used to initialize the object.
     * <p>Invoked after population of normal bean properties but before an init callback such as {@link
     * InitializingBean#afterPropertiesSet()} or a custom init-method. Invoked after {@link
     * ResourceLoaderAware#setResourceLoader}, {@link ApplicationEventPublisherAware#setApplicationEventPublisher} and
     * {@link MessageSourceAware}, if applicable.
     * @param applicationContext the ApplicationContext object to be used by this object
     * @throws ApplicationContextException in case of context initialization errors
     * @throws BeansException              if thrown by application context methods
     * @see BeanInitializationException
     */
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    public String withDynamicThreads(int threads) {

        ThreadWorker threadWorker = null;
        for (int i = 0; i < threads; i++) {
            threadWorker = applicationContext.getBean("threadWorker", ThreadWorker.class);
            threadWorker.setUniqueInfo(String.valueOf(i));
            taskExecutor.execute(threadWorker);
        }

        return UUID.randomUUID().toString();
    }
}

Running a pool with thread workers

The pool will run like normal. One thing to note is that we wanted our pool to continue processing, even if the server is requested to shut down. You can see by the logging that the threads continue to process. Success. The threads operate independent of the web application container and the Spring container.

INFO |Initializing ExecutorService  'taskExecutor' ||org.springframework.scheduling.concurrent.ExecutorConfigurationSupport:165 
INFO |Started runner 4 ||com.javaninja.spring.webmvc.threads.ThreadWorker:48 
INFO |Started runner 1 ||com.javaninja.spring.webmvc.threads.ThreadWorker:48 
INFO |Started runner 2 ||com.javaninja.spring.webmvc.threads.ThreadWorker:48 
INFO |Started runner 5 ||com.javaninja.spring.webmvc.threads.ThreadWorker:48 
INFO |Started runner 3 ||com.javaninja.spring.webmvc.threads.ThreadWorker:48 
INFO |4 sleeping for 8116 ms ||com.javaninja.spring.webmvc.threads.ThreadWorker:52 
INFO |1 sleeping for 586 ms ||com.javaninja.spring.webmvc.threads.ThreadWorker:52 
INFO |2 sleeping for 6754 ms ||com.javaninja.spring.webmvc.threads.ThreadWorker:52 
INFO |5 sleeping for 8060 ms ||com.javaninja.spring.webmvc.threads.ThreadWorker:52 
INFO |3 sleeping for 8841 ms ||com.javaninja.spring.webmvc.threads.ThreadWorker:52 
INFO |Closing org.springframework.context.support.GenericApplicationContext@491cc5c9: startup date [Tue May 10 10:01:27 EDT 2016]; root of context hierarchy ||org.springframework.context.support.AbstractApplicationContext:960 
INFO |Shutting down ExecutorService 'taskExecutor' ||org.springframework.scheduling.concurrent.ExecutorConfigurationSupport:203 
INFO |Runner 1 finishing data=[8aa9a123-5d0f-42d0-8be4-b703705a7a5c, 10de5358-5c7f-4881-9f9d-7706ea6ae8dd, 3f23f9c8-a594-4228-8a91-5eab26fb4d39, 6a52ec9c-82ec-4b88-bfdd-4b413291a8fe, d000aa8c-8c4d-4f6f-9dd5-c63c44431bcd] ||com.javaninja.spring.webmvc.threads.ThreadWorker:63 
INFO |Runner 2 finishing data=[cceed519-1cc9-4ce0-bdf4-02703f624853, 342f024c-c785-47a7-b4b4-aec261341fa7, 56c54700-37ac-41aa-89a2-3d1b4f92b6ed, 2ba81d54-d52b-4b4c-a26a-06996d25c2b9, c7a5e66c-b196-4936-a5aa-5ada8b416b7d] ||com.javaninja.spring.webmvc.threads.ThreadWorker:63 
INFO |Runner 5 finishing data=[159e842e-aaf8-4f86-9e01-1c814043943d, 59fa91bf-cd6a-4ad2-b7bd-8de85d5223f2, 360da0f9-91c8-4682-8d88-23a4f7327b98, a23824c5-f52a-426b-8c16-f5ec223c90cd, 0862d9a1-1635-4d15-8f7f-911877ac7165] ||com.javaninja.spring.webmvc.threads.ThreadWorker:63 
INFO |Runner 4 finishing data=[e26c4269-804c-4a6c-ae08-dc798e6f550c, 709bbf44-f480-4f32-834b-d5c8fc095b81, 807d311d-5a68-48b0-b2a6-cb74d596ee32, e4beeeeb-6628-4261-8a44-dc19a205c71a, a87c24b8-f693-4461-a54d-8a101fbc2a59] ||com.javaninja.spring.webmvc.threads.ThreadWorker:63 
INFO |Runner 3 finishing data=[389b2d85-4a64-4ea8-8b35-39480e027614, 5c85f6d0-a59e-4b7a-95be-e0ab9822e487, efb164c3-dc07-4a73-ae1f-c14c2f05ba08, 33a78ef4-8d67-4566-b20b-c74044012086, e75222f3-bf78-486f-b9e3-9b244f3237e3] ||com.javaninja.spring.webmvc.threads.ThreadWorker:63 

Process finished with exit code 0

Project files

The code for this project is in sheltonn / spring-web-threads

May 10th, 2016

Posted In: Java, java ninja, Javaninja, Spring

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Servlet 3.1 is the latest greatest Servlet API version. I needed to figure out the correct Maven dependencies for using a Servlet 3.1 container, Tomcat 8 specifically. This task was made more difficult because the Java Servlet dependencies tend to move over time. It would be so much better if they were consistent and all one had to do was to change the version numbers. Or better yet, why can’t I include the dependency for Expression Language 3.0 and have it pull in all of its transitive dependencies?

The Tomcat documentation had the following:

Tomcat Servlet API JSP API JSTL API Expression Language API
8.0 3.1 2.3 1.2 3.0

It took a bit of tinkering, but I think I have the Maven dependencies for Servlet 3.1 worked out.

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>javax.servlet.jsp-api</artifactId>
            <version>2.3.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.el</groupId>
            <artifactId>javax.el-api</artifactId>
            <version>3.0.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

Most of the Servlet 3.1 dependencies are packaged by Tomcat 8 and should have their scope marked as provided. The JSTL library is not packaged by Tomcat and cannot be scoped as provided. If you do mark it as provided, you will get the following exception when you try to use JSTL

HTTP Status 500 - Handler processing failed; nested exception is java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config

type Exception report

message Handler processing failed; nested exception is java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config
	org.springframework.web.servlet.DispatcherServlet.triggerAfterCompletionWithError(DispatcherServlet.java:1302)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:977)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:859)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.NoClassDefFoundError: javax/servlet/jsp/jstl/core/Config
	org.springframework.web.servlet.support.JstlUtils.exposeLocalizationContext(JstlUtils.java:101)
	org.springframework.web.servlet.view.JstlView.exposeHelpers(JstlView.java:135)
	org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:142)
	org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
	org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1243)
	org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1027)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:968)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:859)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:844)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.30 logs.

Apache Tomcat/8.0.30

By using the above Maven dependencies, I was able to write a JSP page that used both Expression Language (EL) and JSTL Core Tags. All that is left now is to get to coding the next great webapp that is going to change the world.

April 12th, 2016

Posted In: Glassfish, Java, java ninja, Javaninja, JSP, Servlet Spec, Tomcat

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Spring has a caching abstraction that makes it very easy to add caching to your code without making a log of changes.

I will use this blog to provide an example that uses Spring Java configuration to demonstrate the configuration and usage of the basic cache methods.

Maven Dependencies

The following Maven dependencies are needed to enable the Spring Caching abstraction.

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context-support</artifactId>
    <version>4.2.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>net.sf.ehcache</groupId>
    <artifactId>ehcache</artifactId>
    <version>2.10.1</version>
</dependency>

My entire pom.xml file is below:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.javaninja</groupId>
    <artifactId>spring-ehcache</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>4.2.4.RELEASE</version>
            <exclusions>
                <exclusion>
                    <artifactId>commons-logging</artifactId>
                    <groupId>commons-logging</groupId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>net.sf.ehcache</groupId>
            <artifactId>ehcache</artifactId>
            <version>2.10.1</version>
        </dependency>

        <!--
            Needed for the EqualsBuilder and HashBuilder
        -->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>3.4</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>4.2.4.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.5</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>1.7.16</version>
        </dependency>
    </dependencies>


    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>

    </build>

</project>

Ehcache configuration

Next you will need an ehcache.xml file to configure your cache. An example file is located here.

I defined a cache named cars. It holds 1,000 entries that never expire. If the cache fills up, the first entries are Mine cache is configured as follows:

    <cache name="cars" maxEntriesLocalHeap="1000" eternal="true"/>

My entire ehcache.xml (which contains explanations for the various options) is below:

<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../config/ehcache.xsd">

    <!--<ehcache xsi:noNamespaceSchemaLocation="ehcache.xsd"-->
         <!--updateCheck="true"-->
         <!--monitoring="autodetect"-->
         <!--dynamicConfig="true"-->
         <!--xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">-->
    <!--
        DiskStore configuration
        =======================

        The diskStore element is optional. To turn off disk store path creation, comment out the diskStore
        element below.

        Configure it if you have disk persistence enabled for any cache or if you use
        unclustered indexed search.

        If it is not configured, and a cache is created which requires a disk store, a warning will be
         issued and java.io.tmpdir will automatically be used.

        diskStore has only one attribute - "path". It is the path to the directory where
        any required disk files will be created.

        If the path is one of the following Java System Property it is replaced by its value in the
        running VM. For backward compatibility these should be specified without being enclosed in the ${token}
        replacement syntax.

        The following properties are translated:
        * user.home - User's home directory
        * user.dir - User's current working directory
        * java.io.tmpdir - Default temp file path
        * ehcache.disk.store.dir - A system property you would normally specify on the command line
          e.g. java -Dehcache.disk.store.dir=/u01/myapp/diskdir ...

        Subdirectories can be specified below the property e.g. java.io.tmpdir/one

        -->
    <diskStore path="java.io.tmpdir"/>
    <!--
        TransactionManagerLookup configuration
        ======================================
        This class is used by ehcache to lookup the JTA TransactionManager use in the application
        using an XA enabled ehcache. If no class is specified then DefaultTransactionManagerLookup
        will find the TransactionManager in the following order

         *GenericJNDI (i.e. jboss, where the property jndiName controls the name of the
                        TransactionManager object to look up)
         *Bitronix
         *Atomikos

        You can provide you own lookup class that implements the
        net.sf.ehcache.transaction.manager.TransactionManagerLookup interface.
        -->
    <transactionManagerLookup class="net.sf.ehcache.transaction.manager.DefaultTransactionManagerLookup"
                              properties="jndiName=java:/TransactionManager"
                              propertySeparator=";"/>
    <!--
        CacheManagerEventListener
        =========================
        Specifies a CacheManagerEventListenerFactory which is notified when Caches are added
        or removed from the CacheManager.

        The attributes of CacheManagerEventListenerFactory are:
        * class - a fully qualified factory class name
        * properties - comma separated properties having meaning only to the factory.

        Sets the fully qualified class name to be registered as the CacheManager event listener.

        The events include:
        * adding a Cache
        * removing a Cache

        Callbacks to listener methods are synchronous and unsynchronized. It is the responsibility
        of the implementer to safely handle the potential performance and thread safety issues
        depending on what their listener is doing.

        If no class is specified, no listener is created. There is no default.
        -->
    <cacheManagerEventListenerFactory class="" properties=""/>
    <!--
        TerracottaConfig
        ========================
        (Enable for Terracotta clustered operation)

        Note: You need to install and run one or more Terracotta servers to use Terracotta clustering.
        See http://www.terracotta.org/web/display/orgsite/Download.

        Specifies a TerracottaConfig which will be used to configure the Terracotta
        runtime for this CacheManager.

        Configuration can be specified in two main ways: by reference to a source of
        configuration or by use of an embedded Terracotta configuration file.

        To specify a reference to a source (or sources) of configuration, use the url
        attribute.  The url attribute must contain a comma-separated list of:
        * path to Terracotta configuration file (usually named tc-config.xml)
        * URL to Terracotta configuration file
        * <server host>:<port> of running Terracotta Server instance

        Simplest example for pointing to a Terracotta server on this machine:
        <terracottaConfig url="localhost:9510"/>

        This element has two attributes "rejoin" and "wanEnabledTSA", which can take values of either "true" or "false":
        <terracottaConfig rejoin="true" wanEnabledTSA="true" url="localhost:9510" />

        By default, these attributes are false.

        Without rejoin, if the Terracotta Server is restarted the client cannot connect back to the
        server. When enabled, this allows the client to connect to the new cluster without the
        need to restart the node.

        When wanEnabledTSA is true, the client will wait for the WAN Orchestrator to provide the
        list of WAN enabled caches. Once the Orchestrator is up and running then the client will proceed
        to create the clustered data structures.

        Example using a path to Terracotta configuration file:
        <terracottaConfig url="/app/config/tc-config.xml"/>

        Example using a URL to a Terracotta configuration file:
        <terracottaConfig url="http://internal/ehcache/app/tc-config.xml"/>

        Example using multiple Terracotta server instance URLs (for fault tolerance):
        <terracottaConfig url="host1:9510,host2:9510,host3:9510"/>

        To embed a Terracotta configuration file within the ehcache configuration, simply
        place a normal Terracotta XML config within the <terracottaConfig> element.

        Example:
        <terracottaConfig>
            <tc-config>
                <servers>
                    <server host="server1" name="s1"/>
                    <server host="server2" name="s2"/>
                </servers>
                <clients>
                    <logs>app/logs-%i</logs>
                </clients>
            </tc-config>
        </terracottaConfig>

        For more information on the Terracotta configuration, see the Terracotta documentation.
        -->
    <!--<terracottaConfig url="localhost:9510"/>-->
    <!--
        Cache configuration
        ===================

        The following attributes are required.

        name:
        Sets the name of the cache. This is used to identify the cache. It must be unique.

        maxEntriesLocalHeap:
        Sets the maximum number of objects that will be created in memory.  0 = no limit.
        In practice no limit means Integer.MAX_SIZE (2147483647) unless the cache is distributed
        with a Terracotta server in which case it is limited by resources.

        maxEntriesLocalDisk:
        Sets the maximum number of objects that will be maintained in the DiskStore
        The default value is zero, meaning unlimited.

        eternal:
        Sets whether elements are eternal. If eternal,  timeouts are ignored and the
        element is never expired.

        The following attributes and elements are optional.

        maxEntriesInCache:
        This feature is applicable only to Terracotta distributed caches.
        Sets the maximum number of entries that can be stored in the cluster. 0 = no limit.
        Note that clustered cache will still perform eviction if resource usage requires it.
        This property can be modified dynamically while the cache is operating.

        overflowToOffHeap:
        (boolean) This feature is available only in enterprise versions of Ehcache.
        When set to true, enables the cache to utilize off-heap memory
        storage to improve performance. Off-heap memory is not subject to Java
        GC. The default value is false.

        maxBytesLocalHeap:
        Defines how many bytes the cache may use from the VM's heap. If a CacheManager
        maxBytesLocalHeap has been defined, this Cache's specified amount will be
        subtracted from the CacheManager. Other caches will share the remainder.
        This attribute's values are given as <number>k|K|m|M|g|G for
        kilobytes (k|K), megabytes (m|M), or gigabytes (g|G).
        For example, maxBytesLocalHeap="2g" allots 2 gigabytes of heap memory.
        If you specify a maxBytesLocalHeap, you can't use the maxEntriesLocalHeap attribute.
        maxEntriesLocalHeap can't be used if a CacheManager maxBytesLocalHeap is set.

        Elements put into the cache will be measured in size using net.sf.ehcache.pool.sizeof.SizeOf
        If you wish to ignore some part of the object graph, see net.sf.ehcache.pool.sizeof.annotations.IgnoreSizeOf

        maxBytesLocalOffHeap:
        This feature is available only in enterprise versions of Ehcache.
        Sets the amount of off-heap memory this cache can use, and will reserve.

        This setting will set overflowToOffHeap to true. Set explicitly to false to disable overflow behavior.

        Note that it is recommended to set maxEntriesLocalHeap to at least 100 elements
        when using an off-heap store, otherwise performance will be seriously degraded,
        and a warning will be logged.

        The minimum amount that can be allocated is 128MB. There is no maximum.

        maxBytesLocalDisk:
        As for maxBytesLocalHeap, but specifies the limit of disk storage this cache will ever use.

        timeToIdleSeconds:
        Sets the time to idle for an element before it expires.
        i.e. The maximum amount of time between accesses before an element expires
        Is only used if the element is not eternal.
        Optional attribute. A value of 0 means that an Element can idle for infinity.
        The default value is 0.

        timeToLiveSeconds:
        Sets the time to live for an element before it expires.
        i.e. The maximum time between creation time and when an element expires.
        Is only used if the element is not eternal.
        Optional attribute. A value of 0 means that and Element can live for infinity.
        The default value is 0.

        diskExpiryThreadIntervalSeconds:
        The number of seconds between runs of the disk expiry thread. The default value
        is 120 seconds.

        diskSpoolBufferSizeMB:
        This is the size to allocate the DiskStore for a spool buffer. Writes are made
        to this area and then asynchronously written to disk. The default size is 30MB.
        Each spool buffer is used only by its cache. If you get OutOfMemory errors consider
        lowering this value. To improve DiskStore performance consider increasing it. Trace level
        logging in the DiskStore will show if put back ups are occurring.

        clearOnFlush:
        whether the MemoryStore should be cleared when flush() is called on the cache.
        By default, this is true i.e. the MemoryStore is cleared.

        memoryStoreEvictionPolicy:
        Policy would be enforced upon reaching the maxEntriesLocalHeap limit. Default
        policy is Least Recently Used (specified as LRU). Other policies available -
        First In First Out (specified as FIFO) and Less Frequently Used
        (specified as LFU)

        copyOnRead:
        Whether an Element is copied when being read from a cache.
        By default this is false.

        copyOnWrite:
        Whether an Element is copied when being added to the cache.
        By default this is false.

        Cache persistence is configured through the persistence sub-element.  The attributes of the
        persistence element are:

        strategy:
        Configures the type of persistence provided by the configured cache.  This must be one of the
        following values:

        * localRestartable - Enables the RestartStore and copies all cache entries (on-heap and/or off-heap)
        to disk. This option provides fast restartability with fault tolerant cache persistence on disk.
        It is available for Enterprise Ehcache users only.

        * localTempSwap - Swaps cache entries (on-heap and/or off-heap) to disk when the cache is full.
        "localTempSwap" is not persistent.

        * none - Does not persist cache entries.

        * distributed - Defers to the <terracotta> configuration for persistence settings. This option
        is not applicable for standalone.

        synchronousWrites:
        When set to true write operations on the cache do not return until after the operations data has been
        successfully flushed to the disk storage.  This option is only valid when used with the "localRestartable"
        strategy, and defaults to false.

        The following example configuration shows a cache configured for localTempSwap restartability.

        <cache name="persistentCache" maxEntriesLocalHeap="1000">
            <persistence strategy="localTempSwap"/>
        </cache>

        Cache elements can also contain sub elements which take the same format of a factory class
        and properties. Defined sub-elements are:

        * cacheEventListenerFactory - Enables registration of listeners for cache events, such as
          put, remove, update, and expire.

        * bootstrapCacheLoaderFactory - Specifies a BootstrapCacheLoader, which is called by a
          cache on initialisation to prepopulate itself.

        * cacheExtensionFactory - Specifies a CacheExtension, a generic mechanism to tie a class
          which holds a reference to a cache to the cache lifecycle.

        * cacheExceptionHandlerFactory - Specifies a CacheExceptionHandler, which is called when
          cache exceptions occur.

        * cacheLoaderFactory - Specifies a CacheLoader, which can be used both asynchronously and
          synchronously to load objects into a cache. More than one cacheLoaderFactory element
          can be added, in which case the loaders form a chain which are executed in order. If a
          loader returns null, the next in chain is called.

        * copyStrategy - Specifies a fully qualified class which implements
          net.sf.ehcache.store.compound.CopyStrategy. This strategy will be used for copyOnRead
          and copyOnWrite in place of the default which is serialization.

        Example of cache level resource tuning:
        <cache name="memBound" maxBytesLocalHeap="100m" maxBytesLocalOffHeap="4g" maxBytesLocalDisk="200g" />


        Cache Event Listeners
        +++++++++++++++++++++

        All cacheEventListenerFactory elements can take an optional property listenFor that describes
        which events will be delivered in a clustered environment.  The listenFor attribute has the
        following allowed values:

        * all - the default is to deliver all local and remote events
        * local - deliver only events originating in the current node
        * remote - deliver only events originating in other nodes

        Example of setting up a logging listener for local cache events:

        <cacheEventListenerFactory class="my.company.log.CacheLogger"
            listenFor="local" />


        Search
        ++++++

        A <cache> can be made searchable by adding a <searchable/> sub-element. By default the keys
        and value objects of elements put into the cache will be attributes against which
        queries can be expressed.

        <cache>
            <searchable/>
        </cache>


        An "attribute" of the cache elements can also be defined to be searchable. In the example below
        an attribute with the name "age" will be available for use in queries. The value for the "age"
        attribute will be computed by calling the method "getAge()" on the value object of each element
        in the cache. See net.sf.ehcache.search.attribute.ReflectionAttributeExtractor for the format of
        attribute expressions. Attribute values must also conform to the set of types documented in the
        net.sf.ehcache.search.attribute.AttributeExtractor interface

        <cache>
            <searchable>
                <searchAttribute name="age" expression="value.getAge()"/>
            </searchable>
        </cache>


        Attributes may also be defined using a JavaBean style. With the following attribute declaration
        a public method getAge() will be expected to be found on either the key or value for cache elements

        <cache>
            <searchable>
                <searchAttribute name="age"/>
            </searchable>
        </cache>

        In more complex situations you can create your own attribute extractor by implementing the
        AttributeExtractor interface. Providing your extractor class is shown in the following example:

        <cache>
            <searchable>
                <searchAttribute name="age" class="com.example.MyAttributeExtractor"/>
            </searchable>
        </cache>

        Use properties to pass state to your attribute extractor if needed. Your implementation must provide
        a public constructor that takes a single java.util.Properties instance

        <cache>
            <searchable>
                <searchAttribute name="age" class="com.example.MyAttributeExtractor" properties="foo=1,bar=2"/>
            </searchable>
        </cache>

        If you intend to use dynamic attribute extraction (see net.sf.ehcache.Cache.registerDynamicAttributesExtractor) then
        you need to enable it as follows:

        <cache>
            <searchable allowDynamicIndexing="true"/>
        </cache>


        Cache Exception Handling
        ++++++++++++++++++++++++

        By default, most cache operations will propagate a runtime CacheException on failure. An
        interceptor, using a dynamic proxy, may be configured so that a CacheExceptionHandler can
        be configured to intercept Exceptions. Errors are not intercepted.

        It is configured as per the following example:

          <cacheExceptionHandlerFactory class="com.example.ExampleExceptionHandlerFactory"
                                          properties="logLevel=FINE"/>

        Caches with ExceptionHandling configured are not of type Cache, but are of type Ehcache only,
        and are not available using CacheManager.getCache(), but using CacheManager.getEhcache().


        Cache Loader
        ++++++++++++

        A default CacheLoader may be set which loads objects into the cache through asynchronous and
        synchronous methods on Cache. This is different to the bootstrap cache loader, which is used
        only in distributed caching.

        It is configured as per the following example:

            <cacheLoaderFactory class="com.example.ExampleCacheLoaderFactory"
                                          properties="type=int,startCounter=10"/>

        Element value comparator
        ++++++++++++++++++++++++

        These two cache atomic methods:
          removeElement(Element e)
          replace(Element old, Element element)

        rely on comparison of cached elements value. The default implementation relies on Object.equals()
        but that can be changed in case you want to use a different way to compute equality of two elements.

        This is configured as per the following example:

        <elementValueComparator class="com.company.xyz.MyElementComparator"/>

        The MyElementComparator class must implement the is net.sf.ehcache.store.ElementValueComparator
        interface. The default implementation is net.sf.ehcache.store.DefaultElementValueComparator.


        SizeOf Policy
        +++++++++++++

        Control how deep the SizeOf engine can go when sizing on-heap elements.

        This is configured as per the following example:

        <sizeOfPolicy maxDepth="100" maxDepthExceededBehavior="abort"/>

        maxDepth controls how many linked objects can be visited before the SizeOf engine takes any action.
        maxDepthExceededBehavior specifies what happens when the max depth is exceeded while sizing an object graph.
         "continue" makes the SizeOf engine log a warning and continue the sizing. This is the default.
         "abort"    makes the SizeOf engine abort the sizing, log a warning and mark the cache as not correctly tracking
                    memory usage. This makes Ehcache.hasAbortedSizeOf() return true when this happens.

        The SizeOf policy can be configured at the cache manager level (directly under <ehcache>) and at
        the cache level (under <cache> or <defaultCache>). The cache policy always overrides the cache manager
        one if both are set. This element has no effect on distributed caches.

        Transactions
        ++++++++++++

        To enable an ehcache as transactions, set the transactionalMode

        transactionalMode="xa" - high performance JTA/XA implementation
        transactionalMode="xa_strict" - canonically correct JTA/XA implementation
        transactionMode="local" - high performance local transactions involving caches only
        transactionalMode="off" - the default, no transactions

        If set, all cache operations will need to be done through transactions.

        To prevent users keeping references on stored elements and modifying them outside of any transaction's control,
        transactions also require the cache to be configured copyOnRead and copyOnWrite.

        CacheWriter
        ++++++++++++

        A CacheWriter can be set to write to an underlying resource. Only one CacheWriter can be
        configured per cache.

        The following is an example of how to configure CacheWriter for write-through:

            <cacheWriter writeMode="write-through" notifyListenersOnException="true">
                <cacheWriterFactory class="net.sf.ehcache.writer.TestCacheWriterFactory"
                                    properties="type=int,startCounter=10"/>
            </cacheWriter>

        The following is an example of how to configure CacheWriter for write-behind:

            <cacheWriter writeMode="write-behind" minWriteDelay="1" maxWriteDelay="5"
                         rateLimitPerSecond="5" writeCoalescing="true" writeBatching="true" writeBatchSize="1"
                         retryAttempts="2" retryAttemptDelaySeconds="1">
                <cacheWriterFactory class="net.sf.ehcache.writer.TestCacheWriterFactory"
                                    properties="type=int,startCounter=10"/>
            </cacheWriter>

        The cacheWriter element has the following attributes:
        * writeMode: the write mode, write-through or write-behind

        These attributes only apply to write-through mode:
        * notifyListenersOnException: Sets whether to notify listeners when an exception occurs on a writer operation.

        These attributes only apply to write-behind mode:
        * minWriteDelay: Set the minimum number of seconds to wait before writing behind. If set to a value greater than 0,
          it permits operations to build up in the queue. This is different from the maximum write delay in that by waiting
          a minimum amount of time, work is always being built up. If the minimum write delay is set to zero and the
          CacheWriter performs its work very quickly, the overhead of processing the write behind queue items becomes very
          noticeable in a cluster since all the operations might be done for individual items instead of for a collection
          of them.
        * maxWriteDelay: Set the maximum number of seconds to wait before writing behind. If set to a value greater than 0,
          it permits operations to build up in the queue to enable effective coalescing and batching optimisations.
        * writeBatching: Sets whether to batch write operations. If set to true, writeAll and deleteAll will be called on
          the CacheWriter rather than write and delete being called for each key. Resources such as databases can perform
          more efficiently if updates are batched, thus reducing load.
        * writeBatchSize: Sets the number of operations to include in each batch when writeBatching is enabled. If there are
          less entries in the write-behind queue than the batch size, the queue length size is used.
        * rateLimitPerSecond: Sets the maximum number of write operations to allow per second when writeBatching is enabled.
        * writeCoalescing: Sets whether to use write coalescing. If set to true and multiple operations on the same key are
          present in the write-behind queue, only the latest write is done, as the others are redundant.
        * retryAttempts: Sets the number of times the operation is retried in the CacheWriter, this happens after the
          original operation.
        * retryAttemptDelaySeconds: Sets the number of seconds to wait before retrying an failed operation.

        Pinning
        +++++++

        Use this element when data should remain in the cache regardless of resource constraints.
        Unexpired entries can never be flushed to a lower tier or be evicted.

        This element has a required attribute (store) to specify which data tiers the cache should be pinned to:
        * localMemory: Cache data is pinned to the local heap (or off-heap for BigMemory Go and BigMemory Max).
        * inCache: Cache data is pinned in the cache, which can be in any tier cache data is stored.

        Example:
            <pinning store="inCache"/>

        Cache Extension
        +++++++++++++++

        CacheExtensions are a general purpose mechanism to allow generic extensions to a Cache.
        CacheExtensions are tied into the Cache lifecycle.

        CacheExtensions are created using the CacheExtensionFactory which has a
        <code>createCacheCacheExtension()</code> method which takes as a parameter a
        Cache and properties. It can thus call back into any public method on Cache, including, of
        course, the load methods.

        Extensions are added as per the following example:

             <cacheExtensionFactory class="com.example.FileWatchingCacheRefresherExtensionFactory"
                                 properties="refreshIntervalMillis=18000, loaderTimeout=3000,
                                             flushPeriod=whatever, someOtherProperty=someValue ..."/>

        Cache Decorator Factory
        +++++++++++++++++++++++

        Cache decorators can be configured directly in ehcache.xml. The decorators will be created and added to the CacheManager.
        It accepts the name of a concrete class that extends net.sf.ehcache.constructs.CacheDecoratorFactory
        The properties will be parsed according to the delimiter (default is comma ',') and passed to the concrete factory's
        <code>createDecoratedEhcache(Ehcache cache, Properties properties)</code> method along with the reference to the owning cache.

        It is configured as per the following example:

            <cacheDecoratorFactory
          class="com.company.DecoratedCacheFactory"
          properties="property1=true ..." />

        Distributed Caching with Terracotta
        +++++++++++++++++++++++++++++++++++

        Distributed Caches connect to a Terracotta Server Array. They are configured with the <terracotta> sub-element.

        The <terracotta> sub-element has the following attributes:

        * clustered=true|false - indicates whether this cache should be clustered (distributed) with Terracotta. By
          default, if the <terracotta> element is included, clustered=true.

        * copyOnRead=true|false - indicates whether cache values are deserialized on every read or if the
          materialized cache value can be re-used between get() calls. This setting is useful if a cache
          is being shared by callers with disparate classloaders or to prevent local drift if keys/values
          are mutated locally without being put back in the cache.

          The default is false.

        * consistency=strong|eventual - Indicates whether this cache should have strong consistency or eventual
          consistency. The default is eventual. See the documentation for the meaning of these terms.

        * synchronousWrites=true|false

          Synchronous writes (synchronousWrites="true")  maximize data safety by blocking the client thread until
          the write has been written to the Terracotta Server Array.

          This option is only available with consistency=strong. The default is false.

        * concurrency - the number of segments that will be used by the map underneath the Terracotta Store.
          Its optional and has default value of 0, which means will use default values based on the internal
          Map being used underneath the store.

          This value cannot be changed programmatically once a cache is initialized.

        The <terracotta> sub-element also has a <nonstop> sub-element to allow configuration of cache behaviour if a distributed
        cache operation cannot be completed within a set time or in the event of a clusterOffline message. If this element does not appear, nonstop behavior is off.

        <nonstop> has the following attributes:

        *  enabled="true" - defaults to true.

        *  timeoutMillis - An SLA setting, so that if a cache operation takes longer than the allowed ms, it will timeout.

        *  searchTimeoutMillis - If a cache search operation in the nonstop mode takes longer than the allowed ms, it will timeout.

        *  immediateTimeout="true|false" - What to do on receipt of a ClusterOffline event indicating that communications
           with the Terracotta Server Array were interrupted.

        <nonstop> has one sub-element, <timeoutBehavior> which has the following attribute:

        *  type="noop|exception|localReads|localReadsAndExceptionOnWrite" - What to do when a timeout has occurred. Exception is the default.

        Simplest example to indicate clustering:
            <terracotta/>

        To indicate the cache should not be clustered (or remove the <terracotta> element altogether):
            <terracotta clustered="false"/>

        To indicate the cache should be clustered using "eventual" consistency mode for better performance :
            <terracotta clustered="true" consistency="eventual"/>

        To indicate the cache should be clustered using synchronous-write locking level:
            <terracotta clustered="true" synchronousWrites="true"/>
        -->
    <!--
        Default Cache configuration. These settings will be applied to caches
        created programmatically using CacheManager.add(String cacheName).
        This element is optional, and using CacheManager.add(String cacheName) when
        its not present will throw CacheException

        The defaultCache has an implicit name "default" which is a reserved cache name.
        -->
    <defaultCache maxEntriesLocalHeap="0" eternal="false" timeToIdleSeconds="1200" timeToLiveSeconds="1200">
        <terracotta/>
    </defaultCache>

    <cache name="cars" maxEntriesLocalHeap="1000" eternal="true"/>

    <!--
        Sample caches. Following are some example caches. Remove these before use.
        -->
    <!--
        Sample cache named sampleCache1
        This cache contains a maximum in memory of 10000 elements, and will expire
        an element if it is idle for more than 5 minutes and lives for more than
        10 minutes.

        If there are more than 10000 elements it will overflow to the
        disk cache, which in this configuration will go to wherever java.io.tmp is
        defined on your system. On a standard Linux system this will be /tmp"
        -->
<!--
    <cache name="sampleCache1"
           maxEntriesLocalHeap="10000"
           maxEntriesLocalDisk="1000"
           eternal="false"
           diskSpoolBufferSizeMB="20"
           timeToIdleSeconds="300"
           timeToLiveSeconds="600"
           memoryStoreEvictionPolicy="LFU"
           transactionalMode="off">
        <persistence strategy="localTempSwap"/>
    </cache>
-->
    <!--
        Sample cache named sampleCache2
        This cache has a maximum of 1000 elements in memory. There is no overflow to disk, so 1000
        is also the maximum cache size. Note that when a cache is eternal, timeToLive and
        timeToIdle are not used and do not need to be specified.
        -->
<!--
    <cache name="sampleCache2" maxEntriesLocalHeap="1000" eternal="true" memoryStoreEvictionPolicy="FIFO"/>
-->
    <!--
        Sample cache named sampleCache3. This cache overflows to disk. The disk store is
        persistent between cache and VM restarts. The disk expiry thread interval is set to 10
        minutes, overriding the default of 2 minutes.
        -->
<!--
    <cache name="sampleCache3"
           maxEntriesLocalHeap="500"
           eternal="false"
           overflowToDisk="true"
           diskPersistent="true"
           timeToIdleSeconds="300"
           timeToLiveSeconds="600"
           diskExpiryThreadIntervalSeconds="1"
           memoryStoreEvictionPolicy="LFU"></cache>
-->
    <!--
        Sample Terracotta clustered cache named sampleTerracottaCache.
        This cache uses Terracotta to cluster the contents of the cache.
        -->
<!--
    <cache name="sampleTerracottaCache"
           maxBytesLocalHeap="10m"
           eternal="false"
           timeToIdleSeconds="3600"
           timeToLiveSeconds="1800">
        <terracotta/>
    </cache>
-->
    <!--
          Sample xa enabled cache named xaCache
        <cache name="xaCache"
               maxEntriesLocalHeap="500"
               eternal="false"
               timeToIdleSeconds="300"
               timeToLiveSeconds="600"
               diskExpiryThreadIntervalSeconds="1"
               transactionalMode="xa_strict">
        </cache>
        -->
    <!--
          Sample copy on both read and write cache named copyCache
          using the default (explicitly configured here as an example) ReadWriteSerializationCopyStrategy
          class could be any implementation of net.sf.ehcache.store.compound.CopyStrategy
        <cache name="copyCache"
               maxEntriesLocalHeap="500"
               eternal="false"
               timeToIdleSeconds="300"
               timeToLiveSeconds="600"
               diskExpiryThreadIntervalSeconds="1"
               copyOnRead="true"
               copyOnWrite="true">
            <copyStrategy class="net.sf.ehcache.store.compound.ReadWriteSerializationCopyStrategy" />
        </cache>
        -->
    <!--
          Sample, for Enterprise Ehcache only, demonstrating a tiered cache with in-memory, off-heap and disk stores. In this example the in-memory (on-heap) store is limited to 10,000 items ... which for example for 1k items would use 10MB of memory, the off-heap store is limited to 4GB and the disk store is unlimited in size.
        <cache name="tieredCache"
               maxEntriesLocalHeap="10000"
               eternal="false"
               timeToLiveSeconds="600"
               overflowToOffHeap="true"
               maxBytesLocalOffHeap="4g"
               diskExpiryThreadIntervalSeconds="1">
            <persistence strategy="localTempSwap"/>
         </cache>
        -->
    <!--
          Sample, for Enterprise Ehcache only, demonstrating a restartable cache with in-memory and off-heap stores.
        <cache name="restartableCache"
               maxEntriesLocalHeap="10000"
               eternal="true"
               overflowToOffHeap="true"
               maxBytesLocalOffHeap="4g"
             <persistence strategy="localRestartable"/>
         </cache>
         -->
</ehcache>

Spring Configuration

There are three things that are needed to enable the Spring caching abstraction when using Spring Java configuration.

  • @EnableCaching – Enables Spring’s annotation-driven cache management capability, similar to the support found in Spring’s XML namespace.
  • CacheManager – Spring’s central cache manager SPI
  • EhCacheManagerFactoryBean – FactoryBean that exposes an EhCache CacheManager instance

Below is the code:

package com.javaninja.spring.ehcache;

import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.cache.ehcache.EhCacheCacheManager;
import org.springframework.cache.ehcache.EhCacheManagerFactoryBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

/**
 * @author norris.shelton
 */
@Configuration
@ComponentScan
@EnableCaching
public class SpringContext {

    /**
     * Creates a Spring cache manager.
     * @return spring cache manager
     */
    @Bean
    public CacheManager cacheManager() {
        return new EhCacheCacheManager(ehCacheManagerFactoryBean().getObject());
    }

    /**
     * Create the Ehcache manager factory bean.  Set the bean shared property to shared so other users in this
     * classloader can access it.
     * @return Shared Ehcache manager factory bean
     */
    @Bean
    public EhCacheManagerFactoryBean ehCacheManagerFactoryBean() {
        EhCacheManagerFactoryBean ehCacheManagerFactoryBean = new EhCacheManagerFactoryBean();
        ehCacheManagerFactoryBean.setShared(true);
        return ehCacheManagerFactoryBean;
    }
}

Service Code

Below is the service class that I added the caching to. Note the @Cacheable annotation. The simplest @Cacheable call takes the name of the cache to use for the method. The method parameters will form the basis for the cache key and the return object will be the cache value.. I added some logging so that we can use the log to verify that the method was not accessed because there was a cache hit.

package com.javaninja.spring.ehcache;

import org.apache.commons.lang3.RandomStringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

import java.util.LinkedList;
import java.util.List;

/**
 * @author norris.shelton
 */
@Service
public class CarService {

    private Logger logger = LoggerFactory.getLogger(getClass());

    private List<Car> cars = new LinkedList<>();

    /**
     * Creates a new car.
     * @return Car object with values populated.
     */
    public Car createCar() {
        Car car = new Car();
        car.setMake("Make-" + RandomStringUtils.randomAlphabetic(10));
        car.setModel("Model-" + RandomStringUtils.randomAlphabetic(10));
        car.setVin("Vin-" + RandomStringUtils.randomAlphanumeric(30));

        // Add to my list of all cars
        cars.add(car);
        logger.info("added car to list {}", car);

        return car;
    }

    @Cacheable(value = "cars")
    public Car getCar(String vin) {
        logger.info("inside ");
        Car car = null;
        for (Car car1 : cars) {
            logger.info("iterating over car");
            if (car1.getVin().equals(vin)) {
                car = car1;
                logger.info("found car {}", car1);
            }
        }
        return car;
    }
}

Maven Test Dependencies

I added the following dependencies to enable the proper test support.

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>4.2.4.RELEASE</version>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
</dependency>

Junit test

I created a Junit test class. It pre-loads all of the cars into the service’s car list. The test calls the method twice. The first time the cache is empty and every item has to be iterated. The second time, the cache is fully warm and there is no iteration.

package com.javaninja.spring.ehcache;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

/**
 * @author norris.shelton
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = SpringContext.class)
public class TestCarService {

    private Logger logger = LoggerFactory.getLogger(getClass());

    @Autowired
    private CarService carService;

    private String vin;

    /**
     * Creates cars to look for.
     */
    @Before
    public void before() {
        Car car;
        for (int i = 0; i < 10; i++) {
            car = carService.createCar();
            assertNotNull(car);
            assertNotNull(car.getMake());
            assertNotNull(car.getModel());
            assertNotNull(car.getVin());

            // store the value of the last car
            vin = car.getVin();
        }
    }

    /**
     * Tests the get car method.
     * @throws Exception
     */
    @Test
    public void testGetCar() throws Exception {
        // the first time the get cars method is called, the cache is empty
        logger.info("beginning of first run");
        Car car = carService.getCar(vin);  // find the last car added
        assertNotNull(car);
        assertEquals(vin, car.getVin());
        logger.info("end of first run");

        // the second time the get cars method is called, the cache is fully populated
        logger.info("beginning of second run");
        car = carService.getCar(vin);  // find the last car added
        assertNotNull(car);
        assertEquals(vin, car.getVin());
        logger.info("end of first run");
    }
}

Below is the log for the test run. You can clearly see that during the first run, the list of cars has to be iterated over. During the next run, the method is not entered at all. The method call results in a cache hit.

10:07:53.156 [main] INFO  c.j.spring.ehcache.TestCarService - beginning of first run
10:07:53.160 [main] INFO  c.j.spring.ehcache.CarService - inside 
10:07:53.160 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.160 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.160 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.160 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - iterating over car
10:07:53.161 [main] INFO  c.j.spring.ehcache.CarService - found car com.javaninja.spring.ehcache.Car@5456afaa[make=Make-WmlGJCSagi,model=Model-dYdOzzPNHi,vin=Vin-zfXislLcOjxlPWMNBHy6RnmvS5xAWy]
10:07:53.163 [main] INFO  c.j.spring.ehcache.TestCarService - end of first run
10:07:53.163 [main] INFO  c.j.spring.ehcache.TestCarService - beginning of second run
10:07:53.163 [main] INFO  c.j.spring.ehcache.TestCarService - end of first run

Summary

You now have the information needed to enable the base Spring cache abstraction using Ehcache as the implementation.

The example project for this blog entry is located on GitHub at sheltonn / spring-ehcache

February 29th, 2016

Posted In: Ehcache, Java, java ninja, Javaninja, Spring

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