How to manage exceptions thrown in filters in Spring?

I want to use generic way to manage 5xx error codes, let's say specifically the case when the db is down across my whole spring application. I want a pretty error json instead of a stack trace.

For the controllers I have a @ControllerAdvice class for the different exceptions and this is also catching the case that the db is stopping in the middle of the request. But this is not all. I also happen to have a custom CorsFilter extending OncePerRequestFilter and there when i call doFilter i get the CannotGetJdbcConnectionException and it will not be managed by the @ControllerAdvice. I read several things online that only made me more confused.

So I have a lot of questions:

• Do i need to implement a custom filter? I found the ExceptionTranslationFilter but this only handles AuthenticationException or AccessDeniedException.
• I thought of implementing my own HandlerExceptionResolver, but this made me doubt, I don't have any custom exception to manage, there must be a more obvious way than this. I also tried to add a try/catch and call an implementation of the HandlerExceptionResolver (should be good enough, my exception is nothing special) but this is not returning anything in the response, i get a status 200 and an empty body.

Is there any good way to deal with this? Thanks

So this is what I did:

I read the basics about filters here and I figured out that I need to create a custom filter that will be first in the filter chain and will have a try catch to catch all runtime exceptions that might occur there. Then i need to create the json manually and put it in the response.

So here is my custom filter:

public class ExceptionHandlerFilter extends OncePerRequestFilter {

    @Override
    public void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        try {
            filterChain.doFilter(request, response);
        } catch (RuntimeException e) {

            // custom error response class used across my project
            ErrorResponse errorResponse = new ErrorResponse(e);

            response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
            response.getWriter().write(convertObjectToJson(errorResponse));
    }
}

    public String convertObjectToJson(Object object) throws JsonProcessingException {
        if (object == null) {
            return null;
        }
        ObjectMapper mapper = new ObjectMapper();
        return mapper.writeValueAsString(object);
    }
}

And then i added it in the web.xml before the CorsFilter. And it works!

<filter> 
    <filter-name>exceptionHandlerFilter</filter-name> 
    <filter-class>xx.xxxxxx.xxxxx.api.controllers.filters.ExceptionHandlerFilter</filter-class> 
</filter> 


<filter-mapping> 
    <filter-name>exceptionHandlerFilter</filter-name> 
    <url-pattern>/*</url-pattern> 
</filter-mapping> 

<filter> 
    <filter-name>CorsFilter</filter-name> 
    <filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class> 
</filter> 

<filter-mapping>
    <filter-name>CorsFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

I wanted to provide a solution based on the answer of @kopelitsa. The main differences being:

1. Reusing the controller exception handling by using the HandlerExceptionResolver.
2. Using Java config over XML config

---

First, you need to make sure, that you have a class that handles exceptions occurring in a regular RestController/Controller (a class annotated with @RestControllerAdvice or @ControllerAdvice and method(s) annotated with @ExceptionHandler). This handles your exceptions occurring in a controller. Here is an example using the RestControllerAdvice:

@RestControllerAdvice
public class ExceptionTranslator {

    @ExceptionHandler(RuntimeException.class)
    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    public ErrorDTO processRuntimeException(RuntimeException e) {
        return createErrorDTO(HttpStatus.INTERNAL_SERVER_ERROR, "An internal server error occurred.", e);
    }

    private ErrorDTO createErrorDTO(HttpStatus status, String message, Exception e) {
        (...)
    }
}

To reuse this behavior in the Spring Security filter chain, you need to define a Filter and hook it into your security configuration. The filter needs to redirect the exception to the above defined exception handling. Here is an example:

@Component
public class FilterChainExceptionHandler extends OncePerRequestFilter {

    private final Logger log = LoggerFactory.getLogger(getClass());

    @Autowired
    @Qualifier("handlerExceptionResolver")
    private HandlerExceptionResolver resolver;

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {

        try {
            filterChain.doFilter(request, response);
        } catch (Exception e) {
            log.error("Spring Security Filter Chain Exception:", e);
            resolver.resolveException(request, response, null, e);
        }
	}
}

The created filter then needs to be added to the SecurityConfiguration. You need to hook it into the chain very early, because all preceding filter's exceptions won't be caught. In my case, it was reasonable to add it before the LogoutFilter. See the default filter chain and its order in the official docs. Here is an example:

@Configuration
@EnableWebSecurity
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {

    @Autowired
    private FilterChainExceptionHandler filterChainExceptionHandler;

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .addFilterBefore(filterChainExceptionHandler, LogoutFilter.class)
            (...)
    }

}

I come across this issue myself and I performed the steps below to reuse my ExceptionController that is annotated with @ControllerAdvise for Exceptions thrown in a registered Filter.

There are obviously many ways to handle exception but, in my case, I wanted the exception to be handled by my ExceptionController because I am stubborn and also because I don't want to copy/paste the same code (i.e. I have some processing/logging code in ExceptionController). I would like to return the beautiful JSON response just like the rest of the exceptions thrown not from a Filter.

{
  "status": 400,
  "message": "some exception thrown when executing the request"
}

Anyway, I managed to make use of my ExceptionHandler and I had to do a little bit of extra as shown below in steps:

Steps

---

1. You have a custom filter that may or may not throw an exception
2. You have a Spring controller that handles exceptions using @ControllerAdvise i.e. MyExceptionController

Sample code

//sample Filter, to be added in web.xml
public MyFilterThatThrowException implements Filter {
   //Spring Controller annotated with @ControllerAdvise which has handlers
   //for exceptions
   private MyExceptionController myExceptionController; 
   
   @Override
   public void destroy() {
		// TODO Auto-generated method stub
   }
   
   @Override
   public void init(FilterConfig arg0) throws ServletException {
       //Manually get an instance of MyExceptionController
       ApplicationContext ctx = WebApplicationContextUtils
			      .getRequiredWebApplicationContext(arg0.getServletContext());
       
       //MyExceptionHanlder is now accessible because I loaded it manually
       this.myExceptionController = ctx.getBean(MyExceptionController.class); 
   }
 
   @Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		HttpServletResponse res = (HttpServletResponse) response;
        
        try {
           //code that throws exception
        } catch(Exception ex) {
          //MyObject is whatever the output of the below method
          MyObject errorDTO = myExceptionController.handleMyException(req, ex); 
		  
          //set the response object
          res.setStatus(errorDTO .getStatus());
		  res.setContentType("application/json");
		  
          //pass down the actual obj that exception handler normally send
		  ObjectMapper mapper = new ObjectMapper();
		  PrintWriter out = res.getWriter(); 
		  out.print(mapper.writeValueAsString(errorDTO ));
		  out.flush();
				
		  return; 
        }

        //proceed normally otherwise
        chain.doFilter(request, response); 
     }
}

And now the sample Spring Controller that handles Exception in normal cases (i.e. exceptions that are not usually thrown in Filter level, the one we want to use for exceptions thrown in a Filter)

//sample SpringController 
@ControllerAdvice
public class ExceptionController extends ResponseEntityExceptionHandler {
    
    //sample handler
	@ResponseStatus(value = HttpStatus.BAD_REQUEST)
	@ExceptionHandler(SQLException.class)
	public @ResponseBody MyObject handleSQLException(HttpServletRequest request,
			Exception ex){
		ErrorDTO response = new ErrorDTO (400, "some exception thrown when "
				+ "executing the request."); 
		return response;
	}
    //other handlers
}

Sharing the solution with those who wish to use ExceptionController for Exceptions thrown in a Filter.

So, here's what I did based on an amalgamation of the above answers... We already had a GlobalExceptionHandler annotated with @ControllerAdvice and I also wanted to find a way to re-use that code to handle exceptions that come from filters.

The simplest solution I could find was to leave the exception handler alone, and implement an error controller as follows:

@Controller
public class ErrorControllerImpl implements ErrorController {
  @RequestMapping("/error")
  public void handleError(HttpServletRequest request) throws Throwable {
    if (request.getAttribute("javax.servlet.error.exception") != null) {
      throw (Throwable) request.getAttribute("javax.servlet.error.exception");
    }
  }
}

So, any errors caused by exceptions first pass through the ErrorController and are re-directed off to the exception handler by rethrowing them from within a @Controller context, whereas any other errors (not caused directly by an exception) pass through the ErrorController without modification.

Any reasons why this is actually a bad idea?

If you want a generic way, you can define an error page in web.xml:

<error-page>
  <exception-type>java.lang.Throwable</exception-type>
  <location>/500</location>
</error-page>

And add mapping in Spring MVC:

@Controller
public class ErrorController {

    @RequestMapping(value="/500")
    public @ResponseBody String handleException(HttpServletRequest req) {
        // you can get the exception thrown
        Throwable t = (Throwable)req.getAttribute("javax.servlet.error.exception");

        // customize response to what you want
        return "Internal server error.";
    }
}

This is my solution by overriding default Spring Boot /error handler

package com.mypackage;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.web.ErrorAttributes;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.util.Assert;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Map;

/**
 * This controller is vital in order to handle exceptions thrown in Filters.
 */
@RestController
@RequestMapping("/error")
public class ErrorController implements org.springframework.boot.autoconfigure.web.ErrorController {

    private final static Logger LOGGER = LoggerFactory.getLogger(ErrorController.class);

    private final ErrorAttributes errorAttributes;

    @Autowired
    public ErrorController(ErrorAttributes errorAttributes) {
        Assert.notNull(errorAttributes, "ErrorAttributes must not be null");
        this.errorAttributes = errorAttributes;
    }

    @Override
    public String getErrorPath() {
        return "/error";
    }

    @RequestMapping
    public ResponseEntity<Map<String, Object>> error(HttpServletRequest aRequest, HttpServletResponse response) {
        RequestAttributes requestAttributes = new ServletRequestAttributes(aRequest);
        Map<String, Object> result =     this.errorAttributes.getErrorAttributes(requestAttributes, false);

        Throwable error = this.errorAttributes.getError(requestAttributes);

        ResponseStatus annotation =     AnnotationUtils.getAnnotation(error.getClass(), ResponseStatus.class);
        HttpStatus statusCode = annotation != null ? annotation.value() : HttpStatus.INTERNAL_SERVER_ERROR;

        result.put("status", statusCode.value());
        result.put("error", statusCode.getReasonPhrase());

        LOGGER.error(result.toString());
        return new ResponseEntity<>(result, statusCode) ;
    }

}

Just to complement the other fine answers provided, as I too recently wanted a single error/exception handling component in a simple SpringBoot app containing filters that may throw exceptions, with other exceptions potentially thrown from controller methods.

Fortunately, it seems there is nothing to prevent you from combining your controller advice with an override of Spring's default error handler to provide consistent response payloads, allow you to share logic, inspect exceptions from filters, trap specific service-thrown exceptions, etc.

E.g.

@ControllerAdvice
@RestController
public class GlobalErrorHandler implements ErrorController {




@ResponseStatus(HttpStatus.BAD_REQUEST)
@ExceptionHandler(ValidationException.class)
public Error handleValidationException(
final ValidationException validationException) {
return new Error("400", "Incorrect params"); // whatever
}




@ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
@ExceptionHandler(Exception.class)
public Error handleUnknownException(final Exception exception) {
return new Error("500", "Unexpected error processing request");
}




@RequestMapping("/error")
public ResponseEntity handleError(final HttpServletRequest request,
final HttpServletResponse response) {



Object exception = request.getAttribute("javax.servlet.error.exception");

// TODO: Logic to inspect exception thrown from Filters...
return ResponseEntity.badRequest().body(new Error(/* whatever */));




}




@Override
public String getErrorPath() {
return "/error";
}




}
}

When you want to test a state of application and in case of a problem return HTTP error I would suggest a filter. The filter below handles all HTTP requests. The shortest solution in Spring Boot with a javax filter.

In the implementation can be various conditions. In my case the applicationManager testing if the application is ready.

import ...ApplicationManager;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Component
public class SystemIsReadyFilter implements Filter {

	@Autowired
	private ApplicationManager applicationManager;

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		if (!applicationManager.isApplicationReady()) {
			((HttpServletResponse) response).sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, "The service is booting.");
		} else {
			chain.doFilter(request, response);
		}
	}

	@Override
	public void destroy() {}
}

After reading through different methods suggested in the above answers, I decided to handle the authentication exceptions by using a custom filter. I was able to handle the response status and codes using an error response class using the following method.

I created a custom filter and modified my security config by using the addFilterAfter method and added after the CorsFilter class.

@Component
public class AuthFilter implements Filter {
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
    //Cast the servlet request and response to HttpServletRequest and HttpServletResponse
    HttpServletResponse httpServletResponse = (HttpServletResponse) response;
    HttpServletRequest httpServletRequest = (HttpServletRequest) request;
    
    // Grab the exception from the request attribute
    Exception exception = (Exception) request.getAttribute("javax.servlet.error.exception");
    //Set response content type to application/json
    httpServletResponse.setContentType(MediaType.APPLICATION_JSON_VALUE);
    
    //check if exception is not null and determine the instance of the exception to further manipulate the status codes and messages of your exception
    if(exception!=null && exception instanceof AuthorizationParameterNotFoundException){
        ErrorResponse errorResponse = new ErrorResponse(exception.getMessage(),"Authetication Failed!");
        httpServletResponse.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        PrintWriter writer = httpServletResponse.getWriter();
        writer.write(convertObjectToJson(errorResponse));
        writer.flush();
        return;
    }
    // If exception instance cannot be determined, then throw a nice exception and desired response code.
    else if(exception!=null){
            ErrorResponse errorResponse = new ErrorResponse(exception.getMessage(),"Authetication Failed!");
            PrintWriter writer = httpServletResponse.getWriter();
            writer.write(convertObjectToJson(errorResponse));
            writer.flush();
            return;
        }
        else {
        // proceed with the initial request if no exception is thrown.
            chain.doFilter(httpServletRequest,httpServletResponse);
        }
    }

public String convertObjectToJson(Object object) throws JsonProcessingException {
    if (object == null) {
        return null;
    }
    ObjectMapper mapper = new ObjectMapper();
    return mapper.writeValueAsString(object);
}
}

SecurityConfig class

    @Configuration
    public class JwtSecurityConfig extends WebSecurityConfigurerAdapter {
    @Autowired
    AuthFilter authenticationFilter;
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.addFilterAfter(authenticationFilter, CorsFilter.class).csrf().disable()
                .cors(); //........
        return http;
     }
   }

ErrorResponse class

public class ErrorResponse  {
private final String message;
private final String description;

public ErrorResponse(String description, String message) {
    this.message = message;
    this.description = description;
}

public String getMessage() {
    return message;
}

public String getDescription() {
    return description;
}}

You can use the following method inside the catch block:

response.sendError(HttpStatus.UNAUTHORIZED.value(), "Invalid token")

Notice that you can use any HttpStatus code and a custom message.

I had the same issue in webflux, going on the theme that someone is looking to resuse there @ControllerAdvice, you do not want to throw a direct exception or return a mono error in the webfilter, however you want to set the response to be the mono error.

    public class YourFilter implements WebFilter {


    @Override
    public Mono<Void> filter(final ServerWebExchange exchange, final WebFilterChain chain) {
        exchange.getResponse().writeWith(Mono.error(new YouException()));
        return chain.filter(exchange)
    }
}

In Filters, we don't have a control with @ControllerAdvice or @RestControllerAdvice to handle our exceptions that could occur at the time of doing the authentication. Because, DispatcherServlet will only come into picture after the Controller class hits. So, we need to do the following.

1. we need to have

   HttpServletResponse httpResponse = (HttpServletResponse) response;

"response" object we can pass it from public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) of GenericFilterBean.java implementation class. 2) We can use the below utility class to write or print our error JSON model or String object into the ServletResponse output stream.

public static void handleUnAuthorizedError(ServletResponse response,Exception e)
{
	ErrorModel error = null;
	if(e!=null)
		error = new ErrorModel(ErrorCodes.ACCOUNT_UNAUTHORIZED, e.getMessage());
	else
		error = new ErrorModel(ErrorCodes.ACCOUNT_UNAUTHORIZED, ApplicationConstants.UNAUTHORIZED);
	
	JsonUtils jsonUtils = new JsonUtils();
	HttpServletResponse httpResponse = (HttpServletResponse) response;
	httpResponse.setContentType(MediaType.APPLICATION_JSON_VALUE);
	httpResponse.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
	try {
		httpResponse.getOutputStream().println(jsonUtils.convertToJSON(error));
	} catch (IOException ex) {
		ex.printStackTrace();
	}
}


public String convertToJSON(Object inputObj) {
		ObjectMapper objectMapper = new ObjectMapper();
		String orderJson = null;
		try {
			orderJson = objectMapper.writeValueAsString(inputObj);
		}
		catch(Exception e){
			e.printStackTrace();
		}
		return orderJson;
	}

Late to the party but we can also use it like this:

@ApiIgnore
@RestControllerAdvice
public class ExceptionHandlerController {

	@Autowired
	private MessageSource messageSource;

And in the filter:

@Component
public class MyFilter extends OncePerRequestFilter {

	@Autowired
	@Qualifier("handlerExceptionResolver")
	private HandlerExceptionResolver exceptionResolver;


    @Override
    protected void doFilterInternal(HttpServletRequest request, @NotNull HttpServletResponse response, @NotNull FilterChain filterChain) {
    		try {
    		  // Some exception
    		} catch (Exception e) {
    			this.exceptionResolver.resolveException(request, response, null, e);
    		}
    	}

You do not need to create a custom Filter for this. We solved this by creating custom exceptions that extend ServletException (which is thrown from the doFilter method, shown in the declaration). These are then caught and handled by our global error handler.

edit: grammar

It's strange because @ControllerAdvice should works, are you catching the correct Exception?

@ControllerAdvice
public class GlobalDefaultExceptionHandler {

    @ResponseBody
	@ExceptionHandler(value = DataAccessException.class)
	public String defaultErrorHandler(HttpServletResponse response, DataAccessException e) throws Exception {
       response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
       //Json return
    }
}

Also try to catch this exception in CorsFilter and send 500 error, something like this

@ExceptionHandler(DataAccessException.class)
@ResponseBody
public String handleDataException(DataAccessException ex, HttpServletResponse response) {
    response.setStatus(HttpStatus.INTERNAL_SERVER_ERROR.value());
    //Json return
}