写一个全局自定义异常

package com.example.springboot.utils;

import lombok.Getter;

@Getter
public class ServerException extends RuntimeException{
    // RuntimeException
    private String code = "500";
    // 重写构造方法
    public ServerException(String msg){
        super(msg);
    }
    // 自定义一个code，msg 返回给前端 方便查看报错信息
    public ServerException(String code,String msg){
        super(msg);
        this.code = code;
    }
}

package com.example.springboot.utils;

import com.example.springboot.pojo.Result;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.ResponseBody;
@ControllerAdvice
public class GlobalException {

    @ExceptionHandler(ServerException.class) // 获取自定义的类
    @ResponseBody // 转成 Json格式
    public Result getError(ServerException e){
        // e.getCode  e.getMessage 获取到自定义信息 和 code 有报错会立马 报错
       return Result.error(e.getCode(),e.getMessage());
    }
}

用法：

package com.example.springboot.server;

import com.example.springboot.mapper.LoginMapper;
import com.example.springboot.pojo.UserData;
import com.example.springboot.utils.ServerException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class ServerLoginImp implements ServerLoginDao {
    @Autowired
    private LoginMapper loginMapper;
    @Override
    public UserData loginByUNameAndPwd(UserData user) {
        UserData userName = loginMapper.ByUserName(user.getUsername());
        if (userName == null){
          throw new ServerException("404","用户不存在,请注册"); // 为空报错 抛出
        }
        UserData login = loginMapper.login(user);
        if (login == null){
            throw new ServerException("404","账号或密码错误"); // 没查出 抛出
        }
        return loginMapper.login(user);
    }
}