@ExceptionHandler can be used at the local level or at the global level. Local level would mean using this annotation within the controller itself to handle the exceptions within that controller only. All error thrown by that controller would be caught by that @ExceptionHandler. But this would mean that if there is a similar exception in a different controller you would have to rewrite the corresponding code again in that controller again locally.
In order to prevent repeating this style of exception handling per controller we can write the @ExceptionHanlder at the global level with the help of another annotation called @ControllerAdvice.
@ControllerAdvice is not specific to the exception handling , its also used for handling property, validation or formatter bindings at the global level. @ControllerAdvice in the context of exception handling is just another way of doing exception handling at a global level using @Exceptionhandler annotation.
Now coming to the HandlerExceptionResolver - this is an interface at a more lower level. Spring provides 2 implementations of this:
- ResponseStatusExceptionResolver :This supports the support the @ResponseStatus annotation
- ExceptionHandlerExceptionResolver : This supports the @ExceptionHandler annotation
Example : So when you want to handle exceptions and choose an exception handling strategy you will need to think of choosing between using a local or global exception handling via the annotations. How you need to provide the HTTP status codes, how to wrap it in the @Response entity etc, how you want to redirect to handler pages , carry the data via flash attributes or get params etc etc. Or maybe skip the annotations and use the SimpleMappingExceptionResolver and start mapping the specific exceptions to the error handler page urls
Here we are not be considering the lower level underlying HandlerExceptionResolver at this stage since we are dealing with its implementation at a higher level and building the strategy based on these options.
With the above context to answer your query - @ControllerAdvice was not introduced for exception handling, it's a mechanism you can leverage to handle exceptions globally using the @ExceptionHandler. HandlerExceptionResolver is an interface whose implementation helps support the @ResponseStatus and the @Exceptionhandler annotations. Unless you want to handle the exceptions related to the MVC system because the Spring framework does not provide any proper exception handling. So if you need to hand;e issues related to incorrect @Requestmapping etc which would not be caught by a controller as it would not even reach it in the 1st place then an implementation of the HandlerExceptionResolver would be useful
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