notes/pl/java/libfws/spring/boot/features/error-exception-process.txt

2021
https://dzone.com/articles/spring-boot-exception-handling
    https://github.com/SeunMatt/smattme-tutorials/tree/master/spring-boot-exception-handling
https://reflectoring.io/spring-boot-exception-handling/
2019
https://thepracticaldeveloper.com/2019/09/09/custom-error-handling-rest-controllers-spring-boot/
https://dzone.com/articles/spring-rest-service-exception-handling-1
2018
https://dzone.com/articles/customize-error-responses-in-spring-boot

public enum ErrorMessages {
    MISSING_REQUIRED_FIELD("BlaBla..."),
    RECORD_ALREADY_EXISTS("AnotherBla...")

    private String errorMessage;

    public ErrorMessage(String errorMessage) {
        this.errorMessage = errorMessage;
    }

    public String getErrorMessage() {
        return errorMessage;
    }
}

public class UserRestController {
    @PostMapping(...)
    public User createUser(@RequestBody UserDetailsRequestModel userDetails) throws Exception {
        if () {
            throw new Exception(ErrorMessage.MISSING_REQUIRED_FIELD.getErrorMessage());
            //  {
            //    "timestamp": "2018-05-09...",
            //    "status": 500,
            //    "error": "Internal Server Error",
            //    "message": "BlaBla...",
            //    "path": "/users"
            //  }
        }
    }
}

package ...exception.UserServiceException;

public class UserServiceException extend RuntimeException {
    private static final long serialVersionUID = 134l...L;

    public UserServiceException(String message) {
        super(message);
    }
}

public class UserRestController {
    @PostMapping(...)
    public User createUser(@RequestBody UserDetailsRequestModel userDetails) throws UserServiceException {
        if () {
            throw new UserServiceException(ErrorMessage.MISSING_REQUIRED_FIELD.getErrorMessage());
        }
    }
}

package ...exceptions.AppExceptionsHandler;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.context.Request.WebRequest;

@ControllerAdvice
public class AppExceptionsHandler {

    @ExceptionHandler(value = {UserServiceException.class}) 
    public ResponseEntity<Object> handleUserServiceException(UserServiceException ex, WebRequest request) {
        return new ResponseEntity<>(ex.getMessage, new HTTPHeaders(), HTTPStatus.INTERNAL_SERVER_ERROR);
        // no Accept headers
    }
}

public class ErrorMessage {
    private Date timestamp;
    private String errorMessage;

    public ErrorMessage() {
    }

    // getters/setters
}

@ControllerAdvice
public class AppExceptionsHandler {

    @ExceptionHandler(value = {UserServiceException.class}) 
    public ResponseEntity<Object> handleUserServiceException(UserServiceException ex, WebRequest request) {
        ErrorMessage errorMessage = new ErrorMessage(new Date(), ex.getMessage());
        return new ResponseEntity<>(errorMessage, new HTTPHeaders(), HTTPStatus.INTERNAL_SERVER_ERROR);
        // now we can use headers
    }
    @ExceptionHandler(value = {Exception.class}) 
    public ResponseEntity<Object> handleOtherException(Exception ex, WebRequest request) {
        ErrorMessage errorMessage = new ErrorMessage(new Date(), ex.getMessage());
        return new ResponseEntity<>(errorMessage, new HTTPHeaders(), HTTPStatus.INTERNAL_SERVER_ERROR);
    }
}