Spring Boot 返回结果封装及全局异常处理

为什么要进行结果封装

为了让前端能够拿到统一格式的返回结果，后端在返回时，应该用统一的格式进行封装。

如何进行结果封装

1. 定义返回结果信息的枚举类

   public enum ResultInfo {
       SUCCESS(0, "Success"), 
       INCORRECT_USERNAME_OR_PASSWORD(101, "Incorrect username or password");
   
       private final int code;
       private final String msg;
   
       private ResultInfo(int code, String msg) {
           this.code = code;
           this.msg = msg;
       }
   
       public int getCode() {
           return this.code;
       }
   
       public String getMsg() {
           return this.msg;
       }
   }

   状态码和信息可以自定义。

2. 定义返回结果的工具类

   @Data
   public class ReturnResult {
   
       private int code;
       private String msg;
       private Object data;
   
       /**
        * 构造结果，不包含data
        *
        * @param resultInfo 结果信息
        */
       public ReturnResult(ResultInfo resultInfo) {
           this.code = resultInfo.getCode();
           this.msg = resultInfo.getMsg();
           this.data = null;
       }
   
       /**
        * 构造结果，包含data
        *
        * @param resultInfo 结果信息
        * @param data 要返回的数据
        */
       public ReturnResult(ResultInfo resultInfo, Object data) {
           this.code = resultInfo.getCode();
           this.msg = resultInfo.getMsg();
           this.data = data;
       }
   
       /**
        * 返回成功状态码及信息
        *
        * @return ReturnResult
        */
       public static ReturnResult onSuccess() {
           return new ReturnResult(SUCCESS);
       }
   
       /**
        * 返回成功状态码、信息、数据
        *
        * @return ReturnResult
        */
       public static ReturnResult onSuccess(Object data) {
           return new ReturnResult(SUCCESS, data);
       }
   
       /**
        * 返回失败状态码、信息
        *
        * @return ReturnResult
        */
       public static ReturnResult onFail(ResultInfo resultInfo) {
           return new ReturnResult(resultInfo);
       }
   
       /**
        * 返回失败状态码、信息、数据
        *
        * @return ReturnResult
        */
       public static ReturnResult onFail(ResultInfo resultInfo, Object data) {
           return new ReturnResult(resultInfo, data);
       }
   }

3. 测试

   @RestController
   @RequestMapping(produces = "application/json;charset=UTF-8")
   public class LoginController {
   
       @GetMapping("/login")
       public ReturnResult login(String username, String password) {
           // 省略验证登录代码
           if (...) {
               return ReturnResult.onSuccess();
           } else {
               return ReturnResult.onFail(ResultInfo.INCORRECT_USERNAME_OR_PASSWORD);
           }
       }
   }

4. 结果展示

全局异常处理

当服务端出现异常时，为了使前端收到统一格式的响应，我们应该进行全局异常捕获处理成统一的格式返回。

1. 自定义异常类

public class MyException extends RuntimeException {

    private int code;
    private String msg;

    public MyException(ResultInfo resultInfo) {
        this.code = resultInfo.getCode();
        this.msg = resultInfo.getMsg();
    }

    public MyException(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

2. 使用@ControllerAdvice注解捕获异常

@Log4j2
@ControllerAdvice
public class ExceptionHandle {

    @ExceptionHandler(value = NotLoginException.class)
    @ResponseBody
    public ReturnResult notLoginHandler(HttpServletRequest req, NotLoginException e) {
        log.info(e.getMessage());
        // 封装成结果返回一致的格式
        return ReturnResult.onFail(ResultInfo.NOT_LOGIN);
    }

    @ExceptionHandler(value = NotRoleException.class)
    @ResponseBody
    public ReturnResult notLoginHandler(HttpServletRequest req, NotRoleException e) {
        log.info(e.getMessage());
        return ReturnResult.onFail(ResultInfo.NOT_ROLE);
    }

    @ExceptionHandler(value = MyException.class)
    @ResponseBody
    public ReturnResult myExceptionHandler(HttpServletRequest req, MyException e) {
        log.info(e.getMsg());
        return ReturnResult.onFail(e.getCode(), e.getMsg(), null);
    }

    @ExceptionHandler(value = NullPointerException.class)
    @ResponseBody
    public ReturnResult nullPointerExceptionHandler(HttpServletRequest req, NullPointerException e) {
        log.error("{}: {}", e.getClass().getName(), e.getMessage());
        HashMap<String, Object> dataMap = new HashMap<>();
        dataMap.put("errmsg", e.getClass().getName());
        return ReturnResult.onFail(ResultInfo.NULL_POINTER_EXCEPTION, dataMap);
    }

    @ExceptionHandler(value = Exception.class)
    @ResponseBody
    public ReturnResult exceptionHandler(HttpServletRequest req, Exception e) {
        log.error("{}: {}", e.getClass().getName(), e.getMessage());
        HashMap<String, Object> dataMap = new HashMap<>();
        dataMap.put("errmsg", e.getClass().getName());
        return ReturnResult.onFail(ResultInfo.UNKNOWN_ERROR, dataMap);
    }
}

3. 使用

@RestController
@RequestMapping(produces = "application/json;charset=UTF-8")
public class LoginController {

    @GetMapping("/login")
    public ReturnResult login(String username, String password) {
        // 省略验证登录代码
        if (...) {
            return ReturnResult.onSuccess();
        } else {
            throw new MyException(ResultInfo.INCORRECT_USERNAME_OR_PASSWORD);
        }
    }
}