exception handling for filter in spring

Question

I am handling exceptions in spring using @ExceptionHandler. Any exception thrown by controller is caught using method annotated with @ExceptionHandler and action is taken accordingly. To avoid writing @exceptionHandler for every controller i am using @ControllerAdvice annotation.

Everything works fine as expected.

Now i have a filter(Yes, not interceptor, to handle certain requirement) which is implemented using DelegatingFilterProxy and ContextLoaderListener.

When i am throwing the same exception from above filter, its not caught the way it was done in controller case. It is directly thrown to user.

What's wrong in here?

Answer 1

Filters happens before controllers are even resolved so exceptions thrown from filters can't be caught by a Controller Advice.

Filters are a part of the servlet and not really the MVC stack.

Answer 2

As the exception is not raised from a controller but a filter, @ControllerAdvice won't catch it.

So, the best solution i found after looking everywhere was to create a filter for this internal errors:

public class ExceptionHandlerFilter extends OncePerRequestFilter {
    @Override
    public void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        try {
            filterChain.doFilter(request, response);

        } catch (JwtException e) {
            setErrorResponse(HttpStatus.BAD_REQUEST, response, e);
            e.printStackTrace();
        } catch (RuntimeException e) {
            e.printStackTrace();
            setErrorResponse(HttpStatus.INTERNAL_SERVER_ERROR, response, e);
        }
    }

    public void setErrorResponse(HttpStatus status, HttpServletResponse response, Throwable ex){
        response.setStatus(status.value());
        response.setContentType("application/json");
        // A class used for errors
        ApiError apiError = new ApiError(status, ex);
        try {
            String json = apiError.convertToJson();
            System.out.println(json);
            response.getWriter().write(json);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

Add it to your config, i'm using a WebSecurityConfigurerAdapter implementation:

// Custom JWT based security filter
httpSecurity
        .addFilterBefore(authenticationTokenFilterBean(), UsernamePasswordAuthenticationFilter.class);

// Custom Exception Filter for filter
httpSecurity
        .addFilterBefore(exceptionHandlerFilterBean(), JwtAuthenticationTokenFilter.class);

The error class:

public class ApiError {

    private HttpStatus status;
    @JsonSerialize(using = LocalDateTimeSerializer.class)
    @JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "dd-MM-yyyy hh:mm:ss")
    private LocalDateTime timestamp;
    private String message;
    private String debugMessage;

    private ApiError() {
        timestamp = LocalDateTime.now();
    }
    public ApiError(HttpStatus status) {
        this();
        this.status = status;
    }

    public ApiError(HttpStatus status, Throwable ex) {
        this();
        this.status = status;
        this.message = "Unexpected error";
        this.debugMessage = ex.getLocalizedMessage();
    }

    public ApiError(HttpStatus status, String message, Throwable ex) {
        this();
        this.status = status;
        this.message = message;
        this.debugMessage = ex.getLocalizedMessage();
    }

    public String convertToJson() throws JsonProcessingException {
        if (this == null) {
            return null;
        }
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(new JavaTimeModule());
        mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);

        return mapper.writeValueAsString(this);
    }

  //Setters and getters
}