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Global Error handling

A. in spring MVC project

1. send html response for specific error code - 404

  • add html page --> resource/templates/404.html
  • add property server.error.404 = /error/path-404
  • add controller.
  • extract ErrorAttributes from WebRequest 
    @Controller
public class ErrorController
{
    @Autowired  ErrorAttributes errorAttributes    <<<

    @RequestMapping("/error/path-404")
    public String handle404Error(WebRequest webRequest) 
    {
        ErrorAttributeOptions options = ErrorAttributeOptions.of(
            ErrorAttributeOptions.Include.MESSAGE, 
            ErrorAttributeOptions.Include.EXCEPTION
            );

        Map<String, Object> errorAttributes = this.errorAttributes.getErrorAttributes(webRequest, options);
        // errorAttributes has exception detail, which can be include in html page.
        // add it to model object.
        // in html - ${errorAttribite.xxxxx}

        return "404"; //view name
    }
}

B. in REST API

Default handling flow

  • when an exception occurs, it is automatically routed to below path.
  • define server.error.path = /error
  • BasicErrorController is mapped to this path.
  • it processes and send out json response
  • ``` // Sample resposne:

{ "timestamp": "2024-11-20T00:00:00.000+00:00", "status": 404, "error": "Not Found", "message": "No message available", "path": "/some-endpoint" } `` - fact: add more attribute in above response - @Component public class CustomErrorAttributes extendsDefaultErrorAttributes` : just add this bean - check: CustomErrorAttributes.java - add custome attribute

customization-1 : BasicErrorController

  • note: don't define server.error.404,etc
  • when any Exception occurs, it is automatically routed to below path
  • define server.error.path = /my-error-path
  • or just keep /error
  • add new @RestController for above path
  • extract ErrorAttributes from webRequest. like above.
  • will send out json response.
  • @Component class MyBasicErrorController extends ErrorController { @GetMapping(/my-error-path) m()}
  • MyBasicErrorController.java

customization-2 (@ControllerAdvice)

  • httpRequest send > No issue - no 401,no 500, etc > controller method m1() gets executed.
  • next m1() throws exceptions
  • can have different handler for different exception type.
  • @ExceptionHandler(Exception.class) RE<> m1(Exception e, WebRequest request) { use e ... }
  • @ExceptionHandler(Exception2.class) RE<> m1(Exception2 e, WebRequest request) {...}
  • ...

customization-3 :: Disable tomcat Whitelabel-ErrorPage

  • @EnableAutoConfiguration(exclude = {ErrorMvcAutoConfiguration.class}) --> shows Tomcat page then.
  • or, server.error.whitelabel.enabled=false

inbound / outbound flows :green_circle:

case:1 : incoming request failed, then: - /error + BasicErrorController (already). - /my-error + MyBasicErrorController (custom) + inject ErrorAttribute.

case-2 : incoming requested success, but business code failed with Exception. - Global Exception Handling - @ControllerAdvice/@RestControllerAdvice + @ExceptionHandler(Exception.class)