How to show server (Java) Exception message in React.js

Question

I am not able to see the message (in React.js catch block) set while throwing Exception (by server in Java).

Situation: User wants to perform some action (via myService), some verification w.r.t action can be done only on back-end, if that fails how to show the user what was the reason of failure?

Service (Java):

@GetMapping(path = {/*Servive_path*/}, produces = APPLICATION_JSON_VALUE)
public MyClass myService(@RequestParam String param) {
    throw new RuntimeException("This is error message");
}

Action (React.js):

const myServive = (param) => {
  return async (dispatch, getState) => {
    return request({
      url: ENDPOINTS.MY_SERVICE,
      method: methods.GET,
      params: { param }
    })
      .then(res => {
        dispatch(saveResult(res));
        dispatch(
          notify({
            title: "Successful",
            message: "It was successfully.",
            status: 200,
            dismissAfter: CONFIG.NOTIFICATION_TIMEOUT
          })
        );
      })
      .catch(err => {
        console.log("err.data: ", err.data); //Output-> err.data: 
        console.log("err.message: ", err.message); //Output-> err.message: undefined
        dispatch(
          notify({
            title: "Some error occured",
            message: **//Want to set the error message**,
            status: "error",
            dismissAfter: CONFIG.NOTIFICATION_TIMEOUT
          })
        );
      });
  };
};

Want to show the exception message by setting value in massage in catch block of action.

Output

err.data: ""
err.message: undefined

Also,

err.status: 500
err.request.response: ""
err.request.responseText: ""
err.request.responseType: ""
err.request.status: 500
err.request.statusText: ""

Please help.

Answer 1

By default in case of exception Spring return http status 500 with Content-Type: text/html;charset=UTF-8 and generates html page with error description. Your error description will be in the last line of this page after

<div>There was an unexpected error (type=Internal Server Error, status=500).</div>

and will look like

<div>This is error message</div>

Of course you can write crutch in your code and parse this page using React, but I wouldn't recommend so. It's much better to add Controller advice and write custom exception handling. In your case something like this

import lombok.Value;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestControllerAdvice;

@RestControllerAdvice
public class ErrorHandler {

    @ExceptionHandler(Exception.class)
    @ResponseStatus(HttpStatus.INTERNAL_SERVER_ERROR)
    public ExceptionRestResponse handleCustomException(Exception exception) {
        return new ExceptionRestResponse(500, exception.getMessage());
    }

    @Value
    public static class ExceptionRestResponse {
        int code;
        String message;
    }
} 

Then you will get response with Content-Type: application/json which will look like

{
    "code": 500,
    "message": "This is error message"
} 

Answer 2

You can use the ResponseStatusException to send error message to reactjs .

@RequestMapping(method = RequestMethod.GET, value = "/get")
public List<MyInfo> getInfo(){
   try {
          // code to return
       } catch (InvalidObjectException | InvalidOperationException | OperationNotPermittedException | UserPermissionNotAvailableException e) {
    // throwing custom exceptions
    throw new ResponseStatusException(HttpStatus.FORBIDDEN, e.getMessage(), e);
        } 
   catch (Exception e) {
        throw new ResponseStatusException(HttpStatus.INTERNAL_SERVER_ERROR, e.getMessage(), e);
       }
   }

Instead of e.getMessage() , you may use a specific error message.

Run console.error(error) to see the structure of the error response and display it accordingly. The error response may look like this:

"error" : {
     "status": 403,
     "statusText": "FORBIDDEN",
     "message": "User does not have permission to perform this operation",
     "timestamp": "2020-05-08T04:28:32.917+0000"
     ....
}

More here: https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/server/ResponseStatusException.html