架构之全局错误异常定义

小灰灰 2023-06-17 03:59 9阅读 0赞

# 异常简介 #

## 说明 ##

一个开发框架少不了异常处理机制，让所有的错误集中在一个地方处理，在业务代码开发的时候，往外抛就可以了，由上层统一拦截处理、返回给调用方。这里我们使用了自定义错误码，并将错误码定义在了错误码枚举类中，当然如果你的系统比较庞大，错误码非常多，并且要实现错误码的动态调整，那么也可以将错误码存在数据库中，启动后放到内存缓存，这里为了方便大家理解只是提前将错误码定义在了枚举类中。

## UML图 ##

![自定义异常][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5nY2hhbmdiaW4xMjM_size_16_color_FFFFFF_t_70]![异常处理][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5nY2hhbmdiaW4xMjM_size_16_color_FFFFFF_t_70 1]

# 异常定义 #

## 错误码定义 ##

通过实现此接口扩展应用程序中的错误代码

public interface ErrorCodeI {
    
        public String getErrCode();
    
        public String getErrDesc();
    
    }

## 基础错误码定义 ##

定义3个基本错误代码

public enum BasicErrorCode implements ErrorCodeI {
    
        BIZ_ERROR("BIZ_ERROR" , "通用的业务逻辑错误"),
    
        ZCB_ERROR("ZCB_FRAMEWORK_ERROR" , "ZCB框架错误"),
    
        SYS_ERROR("SYS_ERROR" , "未知的系统错误" );
    
        private String errCode;
    
        private String errDesc;
    
        private BasicErrorCode(String errCode, String errDesc){
            this.errCode = errCode;
            this.errDesc = errDesc;
        }
    
        @Override
        public String getErrCode() {
            return errCode;
        }
    
        @Override
        public String getErrDesc() {
            return errDesc;
        }
    }

## 基础异常信息定义 ##

基异常是所有异常的父级，需要继承运行时异常RuntimeException

public abstract class BaseException extends RuntimeException{
    
        private static final long serialVersionUID = 1L;
        
        private ErrorCodeI errCode;
        
        public BaseException(String errMessage){
            super(errMessage);
        }
        
        public BaseException(String errMessage, Throwable e) {
            super(errMessage, e);
        }
        
        public ErrorCodeI getErrCode() {
            return errCode;
        }
        
        public void setErrCode(ErrorCodeI errCode) {
            this.errCode = errCode;
        }
        
    }

## 框架异常定义 ##

扩展框架的基础结构异常

public class ZCBException extends BaseException {
        
        private static final long serialVersionUID = 1L;
        
        public ZCBException(String errMessage){
            super(errMessage);
            this.setErrCode(BasicErrorCode.ZCB_ERROR);
        }
        
        public ZCBException(String errMessage, Throwable e) {
            super(errMessage, e);
            this.setErrCode(BasicErrorCode.ZCB_ERROR);
        }
    }

## 通用业务异常定义 ##

扩展框架的业务已知异常

public class BizException extends BaseException {
    
        private static final long serialVersionUID = 1L;
    
        public BizException(String errMessage){
            super(errMessage);
            this.setErrCode(BasicErrorCode.BIZ_ERROR);
        }
    
        public BizException(ErrorCodeI errCode, String errMessage){
            super(errMessage);
            this.setErrCode(errCode);
        }
    
        public BizException(String errMessage, Throwable e) {
            super(errMessage, e);
            this.setErrCode(BasicErrorCode.BIZ_ERROR);
        }
    }

## 系统异常定义 ##

扩展框架系统意外异常

public class SysException extends BaseException {
    
        private static final long serialVersionUID = 4355163994767354840L;
    
        public SysException(String errMessage){
            super(errMessage);
            this.setErrCode(BasicErrorCode.SYS_ERROR);
        }
    
        public SysException(ErrorCodeI errCode, String errMessage) {
            super(errMessage);
            this.setErrCode(errCode);
        }
    
        public SysException(String errMessage, Throwable e) {
            super(errMessage, e);
            this.setErrCode(BasicErrorCode.SYS_ERROR);
        }
    
        public SysException(String errMessage, ErrorCodeI errorCode, Throwable e) {
            super(errMessage, e);
            this.setErrCode(errorCode);
        }
    }

# 异常处理 #

## 异常处理接口定义 ##

ExceptionHandlerI提供了一个后门，应用程序可以覆盖默认的异常处理

public interface ExceptionHandlerI {
        public void handleException(Command cmd, Response response, Exception exception);
    }

## 异常处理工厂 ##

这里提供一种扩展机制，如果自己有实现异常处理机制，则执行自定义的异常处理，没有就走默认的异常处理机制。

public class ExceptionHandlerFactory {
    
        public static ExceptionHandlerI getExceptionHandler(){
            try {
                return ApplicationContextHelper.getBean(ExceptionHandlerI.class);
            }
            catch (NoSuchBeanDefinitionException ex){
                return DefaultExceptionHandler.singleton;
            }
        }
    
    }

## 默认异常处理 ##

默认捕获异常并打印日志，并在对应的返回信息返回错误码。

public class DefaultExceptionHandler implements ExceptionHandlerI {
    
        private Log logger = LogFactory.getLog(ExtensionExecutor.class);
    
        public static DefaultExceptionHandler singleton = new DefaultExceptionHandler();
    
        @Override
        public void handleException(Command cmd, Response response, Exception exception) {
            buildResponse(response, exception);
            printLog(cmd, response, exception);
        }
    
        private void printLog(Command cmd, Response response, Exception exception) {
            if(exception instanceof BaseException){
                //biz exception is expected, only warn it
                logger.warn(buildErrorMsg(cmd, response));
            }
            else{
                //sys exception should be monitored, and pay attention to it
                logger.error(buildErrorMsg(cmd, response), exception);
            }
        }
    
        private String buildErrorMsg(Command cmd, Response response) {
            return "Process ["   cmd   "] failed, errorCode: "
                      response.getErrCode()   " errorMsg:"
                      response.getErrMessage();
        }
    
        private void buildResponse(Response response, Exception exception) {
            if (exception instanceof BaseException) {
                ErrorCodeI errCode = ((BaseException) exception).getErrCode();
                response.setErrCode(errCode.getErrCode());
            }
            else {
                response.setErrCode(BasicErrorCode.SYS_ERROR.getErrCode());
            }
            response.setErrMessage(exception.getMessage());
            response.setSuccess(false);
        }
    }

## 异常处理调用 ##

在最上层框架进行调用，为异常处理的总入口。

public Response invoke(Command command) {
            Response response = null;
            try {
                preIntercept(command);
                response = commandExecutor.execute(command);  
            }
            catch(Exception e){
                response = getResponseInstance(command);
                response.setSuccess(false);
                ExceptionHandlerFactory.getExceptionHandler().handleException(command, response, e);
            }
            finally {
                //make sure post interceptors performs even though exception happens
                postIntercept(command, response);
            }          
            return response;
        }

# 使用场景 #

## 系统异常 ##

public static<T> T getBean(Class<T> targetClz){
            T beanInstance = null;
            //优先按type查
            try {
                beanInstance = (T) applicationContext.getBean(targetClz);
            }catch (Exception e){
            }
            //按name查
            if(beanInstance == null){
                String simpleName = targetClz.getSimpleName();
                //首字母小写
                simpleName = Character.toLowerCase(simpleName.charAt(0))   simpleName.substring(1);
                beanInstance = (T) applicationContext.getBean(simpleName);
            }
            if(beanInstance == null){
                new SysException(BasicErrorCode.SYS_ERROR, "Component "   targetClz   " can not be found in Spring Container");
            }
            return beanInstance;
        }

## 业务异常 ##

public static void notNull(Object object, ErrorCodeI errorCode, String message) {
            if (object == null) {
                throw new BizException(errorCode, message);
            }
        }

## 自定义异常 ##

private void checkNull(BizScenario bizScenario){
            if(bizScenario == null){
                throw new ZCBException("BizScenario can not be null for extension");
            }
        }

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