SpringBoot前后端交互、全局异常处理：后端异常信息抛到前端显示弹窗

前提是前端必须有接收后端信息的载体：比如：ajax的异步接收等等。

后端：

编写后端的统一返回信息类：


/**
 * 后端统一返回结果
 * @param <T>
 */
@Data
public class Result<T> implements Serializable {
    private Integer code;//1成功，0和其他数字为失败。
    private String msg;//错误信息
    private T data;//数据

    public static <T> Result<T> success(){
        Result<T> result = new Result<T>();
        result.code=1;
        return result;
    }
    public static <T> Result<T> success(T object){
        Result<T> result = new Result<T>();
        result.data=object;
        result.code=1;
        return result;
    }

    public static <T> Result<T> error(String msg){
        Result<T> result = new Result<T>();
        result.code=0;
        result.msg=msg;
        return result;
    }
}

异常基础类：

/**
 * 业务异常
 */
public class BaseException extends RuntimeException{
    public BaseException(String message) {
        super(message);
    }
    public BaseException() {
    }
}

账号不存在异常：

/**
 * 账号不存在异常
 */
public class AccountNotFoundException extends BaseException {

    public AccountNotFoundException() {
    }

    public AccountNotFoundException(String msg) {
        super(msg);
    }

}

账号密码为空异常：

/**
 * 账号密码为空
 */
public class InputAccountAndPassword extends BaseException{
    public InputAccountAndPassword(String message) {
        super(message);
    }
}

登录失败异常：

/**
 * 登录失败
 */
public class LoginFailedException extends BaseException{
    public LoginFailedException(String msg){
        super(msg);
    }
}

密码错误：

/**
 * 密码错误异常
 */
public class PasswordErrorException extends BaseException {

    public PasswordErrorException() {
    }

    public PasswordErrorException(String msg) {
        super(msg);
    }

}

全局异常类：

/**
 * 全局异常处理
 */
//@ControllerAdvice(annotations = {RestController.class,Controller.class})
//@ResponseBody
@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {
    /**
     * 业务异常
     * @param ex 异常信息
     * @return 封装、抛出给前端
     */
    @ExceptionHandler
    public Result<String> exceptionHandler(BaseException ex){
        log.error(ex.getMessage());
        return Result.error(ex.getMessage());
    }

    @ExceptionHandler
    public Result<String> exceptionHandler(ExpiredJwtException ex){
        String message=ex.getMessage();
        if (message.contains("expired")){
            return Result.error("登录过期！");
        }
        return null;
    }
}

举例：

登录的服务

@Service
@Slf4j
public class LoginServiceImpl implements LoginService {
    @Autowired(required = false)
    private LoginMapper loginMapper;

    /**
     * 用户登录
     * @param user 用户
     */
    public void userLogin(User user) {
        String email = user.getEmail();
        String password = user.getPassword();
        if (email.isEmpty() || password.isEmpty()) {
            //账号密码为空
            throw new InputAccountAndPassword(MessageConstant.ACCOUNT_PASSWORD_EMPTY);
        }
        //账号密码不为空
        else {
            //验证账号
            int i = loginMapper.userExist(email);
            //账号存在
            if (i > 0) {
                //验证密码
                int p = loginMapper.loginCheck(email, password);
                //密码正确
                if (p == 1) {
                    //准许登录 state==1
                    loginMapper.login(email);
                }
                else {
                    //密码错误
                    throw new PasswordErrorException(MessageConstant.PASSWORD_ERROR);
                }
            }
            //账号不存在
            else {
                throw new AccountNotFoundException(MessageConstant.ACCOUNT_NOT_FOUND);
            }
        }
    }
}

异常提示常量类MessageConstant：

/**
 * 信息提示常量类
 */
public class MessageConstant {
    public static final String PASSWORD_ERROR = "密码错误";
    public static final String ACCOUNT_NOT_FOUND = "账号不存在";
    public static final String LOGIN_FAILED = "登录失败";
    public static final String ACCOUNT_PASSWORD_EMPTY="请输入账号和密码";
}

控制端：

@RestController
@RequestMapping("/login")
@Slf4j
public class LoginController {
    @Autowired(required = false)
    private LoginService loginService;
    @Autowired
    private JwtProperties jwtProperties;
    @PostMapping("/userlogin")
    public Result login(@RequestBody User user){
        log.info("开始登录：email:{},password:{}",user.getEmail(),user.getPassword());
        log.info("{}",user);
        loginService.userLogin(user);
        //登录成功后，生成jwt令牌
        Map<String, Object>claims=new HashMap<>();
        claims.put("userId",1L);
        claims.put("email",user.getEmail());
        String token= JwtUtil.createJWT(
                jwtProperties.getUserSecretKey(),
                jwtProperties.getUserTtl(),
                claims);
        UserDTO userDTO = new UserDTO();
        userDTO.setToken(token);
        log.info("生成的token是：{}",token);
        return Result.success(userDTO);
    }
}

前端登录页面以及ajax的测试用例：

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>欢迎登录公司员工考勤管理平台</title>
    <link rel="shortcut icon" th:href="@{/images/icon.svg}">
    <link rel="stylesheet" type="text/css" th:href="@{/css/bootstrap.css}">
    <script th:src="@{/js/jquery-3.2.1.js}"></script>
    <script th:src="@{/js/token.js}"></script>
    <script type="text/javascript">
        $(function () {
            let token=null;
            //登录按钮
            $("#login").click(function () {
                let email=$('#email').val();
                let password=$('#password').val();
                $.ajax({
                    type:"post",
                    url:"/login/userlogin",
                    contentType:"application/json",
                    data:JSON.stringify({"email":email,"password":password}),
                    success:function (result) {
                        if (result.code===1){
                             token=result.data.token;
                            alert("登录成功");
                        //    收到Token，开始存储token
                            localStorage.setItem('token',token);
                            alert("token值为:"+token+"!");
                            //返回Token给后端
                            //返回后端
                            location.href="/main";//也会经过拦截器
                        }else {
                            alert(result.msg);
                        }
                    }
                });
            });

         $("#registry").click(function () {
             location.href="/registry"
         })
        })
    </script>
</head>
<body style="position: absolute;
  top: 20%;
  left: 38%;
  transform: translate(40%,40%);
  margin: 0;padding: 0">
<div>
    <h2>登录页面</h2>
</div>
<div>
    <label for="email"></label><input type="text" id="email" name="email" placeholder="E-mail address">
</div>
<div>
    <label for="password"></label><input type="password" id="password" name="password" placeholder="Password"/>
</div>
<button id="login">登录</button>
<button id="registry">注册</button>
</body>
</html>

测试：

账号密码不为空：