Spring Boot: custom and simple exception handler (using the default payload generated by Spring)

CustomExceptionHandler.java

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.dao.DataAccessException;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;
import org.springframework.web.context.request.WebRequest;
import java.time.LocalDateTime;
import java.util.Map;

@RestControllerAdvice
public class CustomExceptionHandler {

    private static final Logger logger = LoggerFactory.getLogger(CustomExceptionHandler.class);

    @ExceptionHandler(DataAccessException.class)
    public ResponseEntity<?> handleDatabaseErrors(Exception ex, WebRequest request) {

        logger.error("Catching an unhandled database exception thrown by a controller: " + ex.getLocalizedMessage(), ex);

        Map<String, Object> body = Map.of(
                "status", 500,
                "error", "Internal Server Error",
                "path", request.getDescription(false).replace("uri=", ""),
                "timestamp", LocalDateTime.now(),
                "message", "Ocorreu um erro interno. Por favor contate o administrador."
        );
        return ResponseEntity
                .internalServerError().body(body);
    }
}

Spring Boot MockMvc does NOT send payload when there's a expcetion of types ResponseStatusException or MethodArgumentNotValidException during the tests. It happens because MockMvc is NOT a real Servlet environment.

Some issues:

• MockMvc fails to capture the Exception message [SPR-12692]
• ‼️ MockMvc support for testing errors: there are a few interesting solutions here;
• Comment with a workaround
• StackOverflow: Cannot properly test ErrorController Spring Boot

Here one of many workarounds to handle this issue:

import org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController
import org.springframework.boot.web.servlet.error.ErrorController
import org.springframework.http.ResponseEntity
import org.springframework.validation.BindException
import org.springframework.web.bind.MethodArgumentNotValidException
import org.springframework.web.bind.annotation.ControllerAdvice
import org.springframework.web.bind.annotation.ExceptionHandler
import javax.servlet.http.HttpServletRequest

/**
 * This advice is necessary because MockMvc is not a real servlet environment, therefore it does not redirect error
 * responses to [ErrorController], which produces validation response. So we need to fake it in tests.
 * It's not ideal, but at least we can use classic MockMvc tests for testing error response + document it.
 */
@ControllerAdvice
internal class MockMvcValidationConfiguration(private val errorController: BasicErrorController) {

    // add any exceptions/validations/binding problems
    @ExceptionHandler(MethodArgumentNotValidException::class, BindException::class)
    fun defaultErrorHandler(request: HttpServletRequest, ex: Exception): ResponseEntity<*> {
        request.setAttribute("javax.servlet.error.request_uri", request.pathInfo)
        request.setAttribute("javax.servlet.error.status_code", 400)
        return errorController.error(request)
    }
}

And a Java version:

import org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController;
import org.springframework.context.annotation.Profile;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.BindException;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

import javax.servlet.http.HttpServletRequest;

/**
 * This advice is necessary because MockMvc is not a real servlet environment, therefore it does not redirect error
 * responses to [ErrorController], which produces validation response. So we need to fake it in tests.
 * It's not ideal, but at least we can use classic MockMvc tests for testing error response + document it.
 */
@Profile("test")
@ControllerAdvice
public class KeepErrorMessagesWithMockMvcAdvice {

    private final BasicErrorController errorController;

    public KeepErrorMessagesWithMockMvcAdvice(BasicErrorController errorController) {
        this.errorController = errorController;
    }

    // add any exceptions/validations/binding problems
    @ExceptionHandler({ MethodArgumentNotValidException.class, BindException.class } )
    public ResponseEntity<?> defaultErrorHandler(Exception e, HttpServletRequest request) {
        request.setAttribute("javax.servlet.error.status_code", 400);
        request.setAttribute("javax.servlet.error.request_uri", request.getPathInfo());
        return errorController.error(request);
    }
}

Since Spring Boot 2.6.x we need to include server errors explicitly, stacktrace etc.

So, configure your application.properties like this:

server.error.include-message=always
server.error.include-binding-errors=always
server.error.include-stacktrace=on_param
server.error.include-exception=false

Or configure your application.yml like this:

server:
  error:
    include-message: always
    include-binding-errors: always
    include-stacktrace: on_param
    include-exception: false