基于Spring的异常封装

对于前后端分离的Restful架构的服务端应用而言，需要保证在任何情况下都要正常响应前端的请求信息，包括处理过程中发生异常时。这就得针对异常进行统一的封装处理，保证前台能正常解析应答信息。

1.统一异常对象

自定义统一的异常对象有助于我们对异常的处理，这是我们返回给前台错误信息的统一接口。

public class SrvException extends RuntimeException {

    private static final long serialVersionUID = 3162989605548935100L;

    private String code;
    private String msg;

    private Object data;

    public SrvException() {

    }

    public SrvException(CodeMsg cm) {
        this(cm.getCode(), cm.getMsg(), null);
    }

    public SrvException(String code, String msg) {
        this(code, msg, null);
    }

    public SrvException(String code, String msg, Exception e) {
        this(code, msg, null, e);
    }

    public SrvException(String code, String msg, Object data) {
        this(code, msg, data, null);
    }

    public SrvException(String code, String msg, Object data, Exception e) {
        super(msg, e);
        this.code = code;
        this.msg = msg;
        this.data = data;
    }

    public String getCode() {
        return code;
    }

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

    public String getMsg() {
        return msg;
    }

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

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }

    @Override
    public String toString() {
        return "Code:" + code + " Msg:" + msg + " Data:" + JsonHelper.toJson(data);
    }

}

2.统一异常定义

这个类中定义了所有当前系统中抛出的异常信息。

public class CodeMsgDef {
    public static CodeMsg SUCCESS = new CodeMsg(ErrorCodeDef.SUCCESS, "SUCCESS");
    public static CodeMsg ERROR = new CodeMsg(ErrorCodeDef.ERROR, "ERROR");
    
    public static CodeMsg 系统错误 = new CodeMsg(ErrorCodeDef.RUNTIME_ERROR, "未知系统错误！");
    public static CodeMsg 参数错误 = new CodeMsg(ErrorCodeDef.PARAMETER_ERROR, "参数错误!");
    public static CodeMsg 必填参数为空 = new CodeMsg(ErrorCodeDef.PARAMETER_ERROR, "必填参数不能为空！");
    public static CodeMsg 无权限查看 = new CodeMsg(ErrorCodeDef.PURVIEW_ERROR, "无权限查看！");
    public static CodeMsg 不可修改状态 = new CodeMsg(ErrorCodeDef.NOT_UPDATE, "不可修改状态！");
}
public class ErrorCodeDef {
    protected static final String SUCCESS = "0";
    protected static final String ERROR = "1";
    protected static final String RUNTIME_ERROR = "2";
    protected static final String PARAMETER_ERROR = "3";
    protected static final String PURVIEW_ERROR = "4";
    protected static final String NOT_UPDATE = "5";
}

tips: 异常定义类可以放在基础包中被各个微服务依赖，用于判断异常来源。

3.可检测异常的处理

对于非运行时异常，我们可以直接 try/catch 之后转换成SrvException:

try {
    //文件上传
} catch (Exception e) {
    log.error("文件处理失败！", e);
    throw new SrvException(CodeMsgDef.FILE_UPLOAD_ERROR);
}

4.业务异常处理

业务异常需要手动抛出，在最外层统一处理。

if (id <= 0) {
    throw new SrvException(CodeMsgDef.参数错误);
}

5.运行时异常处理

运行时异常虽然也可捕获，但是处理过于麻烦，所以也放在最外层统一处理。

6.异常的统一处理

经过上面的处理之后，异常就被区分成 SrvException 和 RuntimeException;

这里再使用 @ControllerAdvice 和 @ExceptionHandler 在系统抛出异常时，针对指定异常做处理。

@ControllerAdvice
public class ExceptionController {

    private static final Logger log = LoggerFactory.getLogger(ExceptionController.class);

    @ExceptionHandler({RuntimeException.class, Exception.class})
    @ResponseBody
    public Object runtimeExceptionHandler(Exception e, HttpServletRequest request, HttpServletResponse response) {
        if (log.isDebugEnabled()) {
            log.debug(e.getMessage(), e);
        } else {
            log.error(e.getMessage(), e);
        }
        return ResponseUtil.instance(CodeMsgDef.系统错误);
    }

    @ExceptionHandler({SrvException.class})
    @ResponseBody
    public Object srvExceptionHandler(SrvException e) {
        if (log.isDebugEnabled()) {
            log.debug("SrvException: msg: " + e.getMsg() + ", code: " + e.getCode(), e);
        } else {
            log.error("SrvException: msg: " + e.getMsg() + ", code: " + e.getCode());
        }
        return ResponseUtil.instance(e);
    }

}

7.工具类

public class ResponseUtil {
    public static Response success(Object obj) {
        if (obj instanceof String) {
            return new Response(CodeMsgDef.SUCCESS, (String) obj);
        } else {
            return new Response(CodeMsgDef.SUCCESS, obj);
        }
    }

    public static Response instance(SrvException e) {
        return new Response(new CodeMsg(e.getCode(),e.getMsg()));
    }

    public static Response instance(CodeMsg codeMsg) {
        return new Response(codeMsg);
    }

    public static Response instance(CodeMsg codeMsg, String msg) {
        return new Response(new CodeMsg(codeMsg.getCode(), msg));
    }

    public static Response instance(CodeMsg codeMsg, Object obj) {
        if (obj instanceof String) {
            return new Response(codeMsg, (String) obj);
        } else {
            return new Response(codeMsg,obj != null ? JsonHelper.toJson(obj) : null);
        }
    }

    public static Response instance(CodeMsg codeMsg, String msg, Object obj) {
        if (obj instanceof String) {
            return new Response(new CodeMsg(codeMsg.getCode(), msg), (String) obj);
        } else {
            return new Response(new CodeMsg(codeMsg.getCode(), msg),obj != null ? JsonHelper.toJson(obj) : null);
        }
    }

}

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