Spring Boot统一接口返回及全局异常处理

前言：

前段时间接手了一个老项目，现在需要在此项目中添加一些新的需求，同事在开发过程中遇到了一些问题？

• 1.成功的状态到底是200还是0啊，订单系统200代表成功，而会员系统却是0代表成功。
• 2.接口返回的结果中，有些是用msg字段表示描述，有些又是用desc字段描述，前段处理起来比较麻烦能不能统一。
• 3.错误提示信息需要支持国际化。

其实这些问题，归根究底还是代码规范问题，我们需要将接口定义和全局异常统一处理，历史项目10多个工程，难道每个工程都去实现一遍，答案可定是不可能的。

1、解决方案

定义公共模块，实现统一接口定义规范和异常处理，其他的系统进行依赖和扩展即可。

2、具体实现

2.1 定义状态码统一接口

public interface BaseResultCode
{
    /**
     * 状态码
     * @return
     */
    int getCode();
    /**
     * 提示信息
     * @return
     */
    String getMsg();
}

2.2 公共模块状态码枚举类

public enum ResultCode implements BaseResultCode
{
    OK(200, "成功"),
    ERROR(300,"系统异常"), 
    NEED_AUTH(301, "非法请求,请重新登录"), 
    PARAMTER_ERROR(302, "参数错误");
    //省略其他定义错误码
    private int code;
    private String msg;
    private ResultCode(int code, String msg)
    {
        this.code = code;
        this.msg = msg;
    }
    public static ResultCode getValue(int code)
    {
        for (ResultCode errorCode : values())
        {
            if (errorCode.getCode() == code)
            {
                return errorCode;
            }
        }
        return null;
    }
   //省略Get、Set方法
 }

2.3 定义全局自定义异常

public class SysException extends RuntimeException
{
    private static final long serialVersionUID = 5225171867523879342L;
    private int code;
    private String msg;
    private Object[] params;
    private BaseResultCode errorCode;
    public SysException()
    {
        super();
    }
    public SysException(String message)
    {
        super(message);
    }
    public SysException(Throwable cause)
    {
        super(cause);
    }
    public SysException(int code ,String message)
    {
        this.code = code;
        this.msg = message;
    }
    public SysException(int code ,String message,  Object[] params)
    {
        this(code, message);
        this.params= params;
    }
    public SysException(String message, Throwable cause)
    {
        super(message, cause);
    }
    public SysException(BaseResultCode errorCode)
    {
        this.errorCode = errorCode;
    }
    public SysException(String message, Object[] params)
    {
        super(message);
        this.params = params;
    }
    public SysException(BaseResultCode errorCode, String message, Object[] params)
    {
        this(message, params);
        this.errorCode = errorCode;
    }
    
    /**
     * Construct by default
     * 
     * @param message
     *            message
     * @param parameters
     *            parameters
     * @param cause
     *            cause
     */
    public SysException(String message, Object[] params, Throwable cause)
    {
        super(message, cause);
        this.params = params;
    }

    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;
    }
    /**
     * @return the params
     */
    public Object[] getParams()
    {
        return params;
    }
    /**
     * @param params
     *            the params to set
     */
    public void setParams(Object[] params)
    {
        this.params = params;
    }
    public BaseResultCode getErrorCode()
    {
        return errorCode;
    }
    public void setErrorCode(BaseResultCode errorCode)
    {
        this.errorCode = errorCode;
    }
    
}

2.4 定义统一接口格式输出类

public class Result implements Serializable
{
    private static final long serialVersionUID = -1773941471021475043L;
    private Object data;
    private int code;
    private String msg;
    public Result()
    {
    }
    public Result(int code, Object data, String msg)
    {
        this.code = code;
        this.data = data;
        this.msg = msg;
    }
    public Result(int code, String desc)
    {
        this(code, null, desc);
    }
    public Result(BaseResultCode errorCode)
    {
        this(errorCode.getCode(), null, errorCode.getMsg());
    }
    public static Result success()
    {
        return success(null);
    }
    public static Result success(Object data)
    {
        Result result = new Result();
        result.setData(data);
        result.setCode(ResultCode.OK.getCode());
        return result;
    }
    public static Result error(String msg)
    {
        Result result = new Result();
        result.setCode(ResultCode.ERROR.getCode());
        result.setMsg(msg);
        return result;
    }
    public static Result error(BaseResultCode baseCode)
    {
        Result result = new Result();
        result.setCode(baseCode.getCode());
        result.setMsg(baseCode.getMsg());
        return result;
    }
}

个人建议：统一接口输出类不要定义为泛型类型

2.5 定义统一接口格式输出类

@RestControllerAdvice
public class SysExceptionHandler
{
    public static Log logger = LogManager.getLogger(SysExceptionHandler.class);
    @ExceptionHandler(Exception.class)
    public Result handleException(HttpServletRequest request,
            Exception ex)
    {
        logger.error("Handle Exception Request Url:{},Exception:{}",request.getRequestURL(),ex);
        Result result = new Result();
        //系统异常
        if (ex instanceof SysException)
        {
            SysException se = (SysException) ex;
            BaseResultCode resultCode =se.getErrorCode();
            if(resultCode==null)
            {
                result = Result.error(se.getMessage());
            }
            else
            {
               result = new Result(resultCode.getCode(),
                                       StringUtil.isNotEmpty(se.getMessage())?se.getMessage():resultCode.getMsg());
            }
        }
        //参数错误
        else if (ex instanceof ConstraintViolationException)
        {
            ConstraintViolationException v = (ConstraintViolationException) ex;
            String message = v.getConstraintViolations().iterator().next()
                    .getMessage();
            result.setCode(ResultCode.PARAMTER_ERROR.getCode());
            result.setMsg(ResultCode.PARAMTER_ERROR.getMsg() + ":" + message);
        }
        //参数错误
        else if (ex instanceof BindException)
        {
            BindException v = (BindException) ex;
            String message = v.getAllErrors().stream().map(ObjectError::getDefaultMessage).collect(Collectors.joining(","));
            result.setCode(ResultCode.PARAMTER_ERROR.getCode());
            result.setMsg(ResultCode.PARAMTER_ERROR.getMsg() + ":" + message);
        }
        //参数错误
        else if (ex instanceof MethodArgumentNotValidException)
        {
            MethodArgumentNotValidException v = (MethodArgumentNotValidException) ex;
            String message = v.getBindingResult().getAllErrors().stream().map(ObjectError::getDefaultMessage).collect(Collectors.joining(","));
            result.setCode(ResultCode.PARAMTER_ERROR.getCode());
            result.setMsg(ResultCode.PARAMTER_ERROR.getMsg() + ":" + message);
        }
        else
        {
           result = new Result(ResultCode.ERROR.getCode(),ExceptionUtil.getErrorMsg(ex));
        }
        logger.info("exception handle reuslt:" + result);
        return result;
    }
}

上述定义已经可以实现全局接口和异常的统一处理，但是存在的如下问题

每个controller都需要返回Reesult类型，且每个方法都需要返回Result.success()或者Result.success(data)的结果，有点重复，需要进行优化。

    @GetMapping("addUser")
    public Result add()
    {
       for(int i=0;i<10;i++)
       {
           TUser user = new TUser();
           //user.setOid(IdWorker.getId());
           user.setName("shareing_"+i);
           user.setAge(i);
           userService.addUser(user);
       }
       return Result.success();
    }

2.6 接口统一输出优化

实现方式只需要实现ResponseBodyAdvice接口，重写beforeBodyWrite方法接口。

@RestControllerAdvice
public class ResponseAdvice implements ResponseBodyAdvice<Object>
{
    private Logger logger = LoggerFactory.getLogger(ResponseAdvice.class);
    @Override
    public boolean supports(MethodParameter returnType,
            Class<? extends HttpMessageConverter<?>> converterType)
    {
        return true;
    }
    @Override
    public Object beforeBodyWrite(Object o, MethodParameter returnType,
            MediaType selectedContentType,
            Class<? extends HttpMessageConverter<?>> selectedConverterType,
            ServerHttpRequest request, ServerHttpResponse response)
    {
        logger.info("before body write param:{}",o);
        if(o instanceof String)
        {
           //序列化结果输出
           return FastJsonUtil.toJSONString(Result.success(o));
        }
        else if (o instanceof Result)
        {
             return o;
        }
        return Result.success(o);
    }
}

经过优化后，controller输出可以根据业务的需求定义输出对象。

 @GetMapping("getUserByName")
    public TUser getUserByName1(@RequestParam String name)
    {
       logger.info("getUserByName paramter name:"+name);
       return userService.getUserByName(name); 
    }

2.7 子系统如何实现

子系统引入common的jar包，

  <dependency>
	    <groupId>com.xx</groupId>
	    <artifactId>xx-common</artifactId>
	    <version>2.0</version>
	</dependency>

3、子系统定义状态码，实现BaseResultCode接口

 public enum OrderModelErrorCode implements BaseResultCode
{
    ORDER_STATUS_ERROR(1000, "订单状态不正确");
    private int code;
    private String msg;
    private UserModelErrorCode(int code, String msg)
    {
        this.code = code;
        this.msg = msg;
    }
    @Override
    public int getCode()
    {
        return code;
    }
    @Override
    public String getMsg()
    {
        return msg;
    }
}

定义异常处理类，继承公共异常处理类SysExceptionHandler

@RestControllerAdvice
public class OrderModalExceptionHandle extends SysExceptionHandler
{
     @Override
    public Result handleException(HttpServletRequest request, Exception ex)
    {
        return super.handleException(request, ex);
        //子系统可以扩展异常处理
    }
}

子系统使用示例：

@Override
public Order getOrder(String orderId)
{
	Order order =getOrder(orderId);
        //相关伪代码
	if(order.getStatus()>120)
	{
	   throw new SysException(OrderModelErrorCode.ORDER_STATUS_ERROR);    
	}
	return order;
}

经过相关项目的重构，已经解决了第一个和第二问题，关于第三个国际化问题，将在后续的文章中讲解。

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