@ControllerAdvice

This annotation is the core of unified exception handling

Design ideas in this category:

• Use the @ ExceptionHandler annotation to catch the specified or customized exception;

• Use @ controlleradvise to integrate the method of @ ExceptionHandler into a class;

• A general exception capture method must be defined to capture undefined exception information;

• Define an exception class to catch exceptions for the project or business;

• The abnormal object information is added to the unified result enumeration;

Custom global exception class

import com.example.demo.util.R;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;

/**
 * Global exception handling class
 */
@ControllerAdvice
public class CommonExceptionHandler {

    /**
     * General exception handling
     * @param ex
     * @return
     */
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public R exceptionHandler(Exception ex) {
        //Output exception information
        ex.printStackTrace();
        //Handling exception information of verification annotation
        if (ex instanceof MethodArgumentNotValidException) {
            MethodArgumentNotValidException mex = (MethodArgumentNotValidException) ex;
            return R.failed(mex.getBindingResult().getFieldErrors().get(0).getDefaultMessage());
        } else {
            return R.failed(ex.getMessage());
        }
    }

    /**
     * Handle an exception separately
     * @param e
     * @return
     */
    @ExceptionHandler(NullPointerException.class)
    @ResponseBody
    public R error(NullPointerException e) {
        //Output exception information
        e.printStackTrace();
        return R.failed("Null pointer exception");
    }
}

This is the main core code.

Code example

1. Project directory:

2.Controller code:

import com.example.demo.model.User;
import com.example.demo.util.R;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.validation.Valid;

/**
 * User login controller
 */
@RestController
@RequestMapping(value = "/user")
public class UserController {

    /**
     * User login
     * @param user
     * @return
     */
    @PostMapping(value = "/login")
    public R login(@Valid @RequestBody User user){
        System.out.println("Login succeeded!");
        return R.ok(user);
    }

}

3.User entity class

import lombok.Data;

import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Size;

/**
 * User login entity class
 */
@Data
public class User {

    @NotBlank(message = "User name cannot be empty")
    private String username;

    @NotBlank(message = "Password cannot be empty")
    @Size(max = 20, min = 6, message = "Password length is 6-20 Between characters")
    private String password;

}

The code of API code enumeration and R return object will not be shown. These two codes refer to the design of R object in mybatis plus. They are relatively simple and can be written at will.

PostMan request test

Seeing this result, our global unified handling of annotation verification exception is successful.