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
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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