Spring的異常統一處理非常簡單，首先我們需要看一下Spring中定義的HandlerExceptionResolver接口：
/**
* Interface to be implemented by objects than can resolve exceptions thrown
* during handler mapping or execution, in the typical case to error views.
* Implementors are typically registered as beans in the application context.
*
* <p>Error views are analogous to the error page JSPs, but can be used with
* any kind of exception including any checked exception, with potentially
* fine-granular mappings for specific handlers.
*
* @author Juergen Hoeller
* @since 22.11.2003
*/
public interface HandlerExceptionResolver {
/**
* Try to resolve the given exception that got thrown during on handler execution,
* returning a ModelAndView that represents a specific error page if appropriate.
* <p>The returned ModelAndView may be {@linkplain ModelAndView#isEmpty() empty}
* to indicate that the exception has been resolved successfully but that no view
* should be rendered, for instance by setting a status code.
* @param request current HTTP request
* @param response current HTTP response
* @param handler the executed handler, or <code>null</code> if none chosen at the
* time of the exception (for example, if multipart resolution failed)
* @param ex the exception that got thrown during handler execution
* @return a corresponding ModelAndView to forward to,
* or <code>null</code> for default processing
*/
ModelAndView resolveException(
HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex);
}
他定義了一個resolveException方法，我們如果要處理異常的話，需要實現這個接口類，並且實現resolveException方法，在resolveException方法中處理自己的異常邏輯。
例如我設計一個自定義的異常處理類：
/**
* 自定義一個異常捕獲處理類
* @author zhuli
* @date 2014-9-3
*/
public class MyExceptionResolver implements HandlerExceptionResolver {
private static final Logger logger = LoggerFactory.getLogger(MyExceptionResolver.class);
@Override
public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
//可以自由處理各種異常邏輯
if (ex instanceof org.springframework.web.HttpRequestMethodNotSupportedException) {
logger.warn(Logger.ACTION.DEFAULT, "Http Method Error");
}
return null;
}
} 然後需要將我們的我們自定義的MyExceptionResolver類注入到bean中
<bean id="MyExceptionResolver" class="com.tiantian.xxx.web.handler.MyExceptionResolver"/> 具體Spring是怎麼調用的？我們可以先看下Spring中的doDispatch方法中，有這麼一段代碼：
catch (ModelAndViewDefiningException ex) {
logger.debug("ModelAndViewDefiningException encountered", ex);
mv = ex.getModelAndView();
}
catch (Exception ex) {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(processedRequest, response, handler, ex);
errorView = (mv != null);
} 其中processHandlerException方法就是來捕獲異常處理的，那麼繼續看processHandlerException這個方法：
protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response,
Object handler, Exception ex) throws Exception {
// Check registered HandlerExceptionResolvers...
ModelAndView exMv = null;
for (HandlerExceptionResolver handlerExceptionResolver : this.handlerExceptionResolvers) {
exMv = handlerExceptionResolver.resolveException(request, response, handler, ex);
if (exMv != null) {
break;
}
}
if (exMv != null) {
if (exMv.isEmpty()) {
return null;
}
// We might still need view name translation for a plain error model...
if (!exMv.hasView()) {
exMv.setViewName(getDefaultViewName(request));
}
if (logger.isDebugEnabled()) {
logger.debug("Handler execution resulted in exception - forwarding to resolved error view: " + exMv, ex);
}
WebUtils.exposeErrorRequestAttributes(request, ex, getServletName());
return exMv;
}
throw ex;
} 這個方法中的handlerExceptionResolver.resolveException就是用來捕獲異常的，並且Spring允許多個自定義的異常類實現。
可以看this.handlerExceptionResolvers方法，跟蹤進去
private void initHandlerExceptionResolvers(ApplicationContext context) {
this.handlerExceptionResolvers = null;
if (this.detectAllHandlerExceptionResolvers) {
// Find all HandlerExceptionResolvers in the ApplicationContext, including ancestor contexts.
Map<String, HandlerExceptionResolver> matchingBeans = BeanFactoryUtils
.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);
if (!matchingBeans.isEmpty()) {
this.handlerExceptionResolvers = new ArrayList<HandlerExceptionResolver>(matchingBeans.values());
// We keep HandlerExceptionResolvers in sorted order.
OrderComparator.sort(this.handlerExceptionResolvers);
}
}
else {
try {
HandlerExceptionResolver her =
context.getBean(HANDLER_EXCEPTION_RESOLVER_BEAN_NAME, HandlerExceptionResolver.class);
this.handlerExceptionResolvers = Collections.singletonList(her);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, no HandlerExceptionResolver is fine too.
}
}
// Ensure we have at least some HandlerExceptionResolvers, by registering
// default HandlerExceptionResolvers if no other resolvers are found.
if (this.handlerExceptionResolvers == null) {
this.handlerExceptionResolvers = getDefaultStrategies(context, HandlerExceptionResolver.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerExceptionResolvers found in servlet '" + getServletName() + "': using default");
}
}
}可以清洗看到這個方法是將handlerExceptionResolvers進行了初始化，並將自定義的異常處理類（可以多個）寫入this.handlerExceptionResolvers
