Java Ninja Chronicles By Norris Shelton

Things I learned in the pursuit of code

In the original blog entry, Throwing exceptions with messages from a SpringMVC controller I set up a system to allow exceptions that would be thrown to cause an HTTP status code to be sent to the consumer with a message.

I needed to expand upon that to handle all of the exceptions that my Spring MVC controllers could encounter. To accomplish that, I created a class and annotated it with @ControllerAdvice. This allowed me to create a ExceptionHandlers for all of my controllers in one place.

I created three mappings because I wanted to handle the three types of exceptions a little differently than the others.

  • ResourceException – allows me to set a HTTP status and a message
  • RuntimeException – these are not typically created by developers I need to grab all of the information that I can. That is why I used the toString. That contains the name of the exception and the system specified message.
  • Exception – these are checked exceptions and are created by developers within their code. The expectation is that they put a meaningful message in the message property.

This was fairly easy to accomplish by having three different exception mappings. Within each exception mapping, I set the values in the ResponseEntity to display the appropriate HTTP status with a message in the content.

package com.javaninja.cam.spring;


import com.javaninja.cam.exception.ResourceException;

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


/**
 * Exception handler advice class for all SpringMVC controllers.
 * @author norrisshelton
 * @see ControllerAdvice
 */
@ControllerAdvice
public class CamControllerAdvice {

    /**
     * Returns whatever HTTP status was set within the ResourceException.  Uses the message that was set when
     * the ResourceException was created.
     * @param e SpringMVC controller exception.
     * @return http response entity
     * @see ExceptionHandler
     */
    @ExceptionHandler(ResourceException.class)
    public ResponseEntity handleResourceException(ResourceException e) {
        return ResponseEntity.status(e.getHttpStatus()).body(e.getMessage());
    }

    /**
     * Sets the HTTP status as INTERNAL_SERVER_ERROR (500).  Uses the toString of the exception because
     * RuntimeExceptions don't always have enough usable information in the message property.
     * @param e SpringMVC controller exception.
     * @return http response entity
     * @see ExceptionHandler
     */
    @ExceptionHandler(RuntimeException.class)
    public ResponseEntity handleRuntimeException(RuntimeException e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.toString());
    }

    /**
     * Sets the HTTP status as INTERNAL_SERVER_ERROR (500).  Uses the message property under the assumption that the
     * developer that created the exception set a meaningful explanation in the message property.
     * @param e SpringMVC controller exception.
     * @return http response entity
     * @see ExceptionHandler
     */
    @ExceptionHandler(Exception.class)
    public ResponseEntity handleException(Exception e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(e.getMessage());
    }
}

November 16th, 2016

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

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