seal

若是月亮还没来
路灯也可照窗台
照着白色的山茶花微微开
若是晨风还没来
晚风也可吹入怀
吹着那一地树影温柔摇摆

Level 6: Exception handling and error prompts

Target: Implement a unified exception handling mechanism to provide friendly error prompts for the front end.

Solution

To solve this problem, I choose to create a new code package —— exception

In this code package, I divided it into two parts below:

1. Custom Exceptions
2. Unified exception collector

Custom Exceptions

package com.example.demo2.exception;

import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.http.HttpStatus;

//The @ResponseStatus annotation can automatically set the HTTP response status code when an exception is thrown
@ResponseStatus(HttpStatus.NOT_FOUND)
public class UserNotFoundException extends RuntimeException {

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

    public UserNotFoundException(Long id){
        super("User with id " + id + " not found");
    }
}

This class extends normal exception , and use super method to create a custom exception

Unified exception collector

package com.example.demo2.exception;

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;

import java.time.LocalDateTime;
import java.util.HashMap;
import java.util.Map;

@ControllerAdvice
//The @ControllerAdvice annotation indicates that this is a global exception handler
// It will intercent all exceptions thrown by @Controller
public class GlobalExceptionHandler {

    @ExceptionHandler(UserNotFoundException.class)
    public ResponseEntity<Map<String,Object>> handleUserNotFoundException(
            UserNotFoundException ex, WebRequest request){
        Map<String,Object> errorDetails = new HashMap<>();
        errorDetails.put("timestamp", LocalDateTime.now());
        errorDetails.put("status", HttpStatus.NOT_FOUND.value());
        errorDetails.put("error", "User not found");
        errorDetails.put("message", ex.getMessage());
        errorDetails.put("path1", request.getContextPath());
        errorDetails.put("path2", request.getDescription(false));
        return new ResponseEntity<>(errorDetails, HttpStatus.NOT_FOUND);
    }

    @ExceptionHandler(Exception.class)
    public ResponseEntity<Map<String, Object>> handleGlobalException(
            Exception ex, WebRequest request){
        Map<String,Object> errorDetails = new HashMap<>();
        errorDetails.put("timestamp", LocalDateTime.now());
        errorDetails.put("status", HttpStatus.INTERNAL_SERVER_ERROR.value());
        errorDetails.put("error", "Internal server error");
        errorDetails.put("message", ex.getMessage());
        errorDetails.put("path2", request.getDescription(false));

        return new ResponseEntity<>(errorDetails, HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

Here devided exceptions into two classes —— UserNotFound and Normal Exception