Exception Handling in SpringBoot

Lets directly see a demo to understand exception handling in Springboot better.
Suppose I have the below api endpoint:

	@GetMapping("/test")
	public String test() {
		return "Working fine";
	}

Obviously the above endpoint will work fine if you call this URL: http://localhost:8080/test
But you will get something like below if you call this URL : http://localhost:8080/some-nonexist-url

It is a good response, you are getting enough information. So, Springboot takes care of these kind of errors.
Now, lets throw an exception and see how Spring boot handles it.

	@GetMapping("/test")
	public String test() {
		if(true)
			throw new MyException("My exception message");
		return "Working fine";
	}

And the MyException class looks like this:

public class MyException extends RuntimeException{
	public MyException(String exception) {
		super(exception);
	}
}

Now if you call the same url : http://localhost:8080/test, below would be the output:

You can see you are getting a generic exception, if you want to make it throw some specific exception you can mention the below annotation on top of MyException class:

@ResponseStatus(HttpStatus.NOT_FOUND)

And then when you hit the same URL again you will see below error:

So by the above way you are customizing the return status for a specific exception.
Lets see now how you can customize the response structure of the exception.
First create the POJO MyExceptionDetails.java class:

public class MyExceptionDetails {
  private Date timestamp;
  private String message;
  private String details;
  
  public MyExceptionDetails(Date timestamp, String message, String details) {
	    super();
	    this.timestamp = timestamp;
	    this.message = message;
	    this.details = details;
  }
  //Add only setters.
}

Then have another class where you define your @ControllerAdvice:

@ControllerAdvice
@RestController
public class MyCustomizedExceptionHandler extends ResponseEntityExceptionHandler{
	
	  @ExceptionHandler(MyException.class)
	  public final ResponseEntity<MyExceptionDetails> handleUserNotFoundException(MyException ex, WebRequest request) {
		  MyExceptionDetails errorDetails = new MyExceptionDetails(new Date(), ex.getMessage(), request.getDescription(false));
	      return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
	  }
}

Now if you call the same URL you will get the exception message in your format: