spring的异常统一处理非常简单，首先我们需要看一下Spring中定义的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.

*

*

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.

*

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 null 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 null for default processing

*/

ModelAndView resolveException(

HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex);

}

他定义了一个resolveException方法，我们如果要处理异常的话，需要实现这个接口类，并且实现resolveException方法，在resolveException方法中处理自己的异常逻辑。 例如我设计一个自定义的异常处理类：

/**

* 自定义一个异常捕获处理类

* @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) {

//可以自由处理各种异常逻辑

if (ex instanceof org.springframework.web.HttpRequestMethodNotSupportedException) {

logger.warn(Logger.ACTION.DEFAULT, "Http Method Error");

}

return null;

}

}

然后需要将我们的我们自定义的MyExceptionResolver类注入到bean中

具体Spring是怎么调用的？我们可以先看下Spring中的doDispatch方法中，有这么一段代码：

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方法就是来捕获异常处理的，那么继续看processHandlerException这个方法：

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;

}

这个方法中的handlerExceptionResolver.resolveException就是用来捕获异常的，并且Spring允许多个自定义的异常类实现。 可以看this.handlerExceptionResolvers方法，跟踪进去

private void initHandlerExceptionResolvers(ApplicationContext context) {

this.handlerExceptionResolvers = null;

if (this.detectAllHandlerExceptionResolvers) {

// Find all HandlerExceptionResolvers in the ApplicationContext, including ancestor contexts.

Map matchingBeans = BeanFactoryUtils

.beansOfTypeIncludingAncestors(context, HandlerExceptionResolver.class, true, false);

if (!matchingBeans.isEmpty()) {

this.handlerExceptionResolvers = new ArrayList(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");

}

}

}

可以清洗看到这个方法是将handlerExceptionResolvers进行了初始化，并将自定义的异常处理类(可以多个)写入this.handlerExceptionResolvers