spring-restful-exception-handler

An annotation for the Spring framework to handle HTTP responses for custom exceptions.

Bean Setup and Properties:

The way it works is you have to change the default exception resolver for Spring to our custom exception resolver by modifying your servlet xml file for Spring:

<bean id="exceptionResolver" class="com.github.raychatter.AnnotationHandler">
   <property name="useHandledExceptionMessage" value="true"/>
   <property name="useGetCause" value="true"/>
</bean>

There are two boolean properties that can be set within the spring-restful-exception-handler bean:

useGetCause (true by default) If an unannotated exception is thrown and useGetCause is true, the spring-restful-exception-handler will call getCause() on the exception until the first annotated exception is found. Provided there is no annotated exception or useGetcause is set to false, the default httpStatus and contentType will be used with the thrown exception.

useHandledExceptionMessage (true by default) Sometimes it is useful to give the user a "higher level" exception response message than the one associated with the handled (annotated) exception. When useHandledExceptionMessage is true (which is the default setting), the message returned will be that from the annotated exception. If this property or useGetCause is set to false or there is no annotated exception, the message used will be from the thrown exception.

Annotate the Custom Exception Class:

After overriding the exception resolving mechanism, just annotate the custom exception classes with @ExceptionHandler(*httpStatus*, *contentType*). The defaults are httpStatus = HttpStatus.INTERNAL_SERVER_ERROR and contentType = MediaType.APPLICATION_XML_VALUE. So an example exception class would be:

@ExceptionHandler(httpStatus = HttpStatus.NOT_FOUND, contentType = MediaType.APPLICATION_XML_VALUE)
public class MyCustomException extends Exception {
   public MyCustomException(final String message) {
      super(message);
   }
}

The custom message is taken from the custom annotation class itself, so any parameters you'd like to insert need to be handled there.

And that's it! Just keep in mind that the exception handler will take care of all the exceptions and by default it will return Internal Server Error with an XML body described above.

Error Response Template:

If you don't specify any custom template for your error responses, following error template will be used by default:

<?xml version="1.0" encoding="UTF-8"?>
<error>
   %s
</error>

If you want to override the default template, make sure you have error.template in your classpath with %s for the message placeholder. An example for a error.template file in your classpath for a json response:

{
   "message": "%s"
}

And now you need to make sure that your exceptions are returning json content type.

@ExceptionHandler(httpStatus = HttpStatus.CONFLICT, contentType = MediaType.APPLICATION_JSON_VALUE)
public class MyCustomException extends Exception {
   public MyCustomException(final String message) {
      super(message);
   }
}

And that's it!