spring3.0异常处理进阶

spring3.0开发不可避免要遇到异常处理，如果只有jsp请求能捕获到异常，是不足够的， 有时候AJAX返回json数据时遇到异常。这时候默认的处理方式不能满足了， 需要自定义的方式支持同步和ajax异步异常处理。

或许大家都知道spring3的异常处理方法有：

1 以配置文件的方式进行异常管理

在配置dispacher-servlet.xml

<bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver"> <property name="defaultErrorView"> <value>jsonView</value> </property> <property name="exceptionMappings"> <props> <prop key="java.lang.Exception">/common/error.jsp</prop> </props> </property> </bean>

配置多个异常处理的地方

2以注解的方式配置异常管理

为了方便阅读， 把代码的地方发全一点

@Controller public class ExceptionHandlerController { private final Logger log = LoggerFactory.getLogger(getClass()); @ExceptionHandler(ManagerSecurityException.class) public ModelAndView handleManagerSecurityException(ManagerSecurityException e, HttpServletResponse response) throws IOException { log.info("Manager exception handler " + e.getMessage()); response.sendError(HttpServletResponse.SC_FORBIDDEN, e.getMessage()); return new ModelAndView("viewName",new HashMap()); } }

这样的配置处理jstl请求jsp没有问题，

如果是jquery的 $.post的方法请求， 那么如果还是返回 error.jsp ， 那在 js的success函数里则不能很好地输出显示了。

问题又来了： 如果在 handleManagerSecurityException方法的上面打上注解 @ResponeBody

那么这样又只能返回 json格式串的异常处理， 你想同步请求跳到到error.jsp又不行啦！

解决办法是这样的：定制化异常处理

<bean id="exceptionResolver" class="com.wsd.core.web.servlet.handle.CustomSimpleMappingExceptionResolver"> <property name="defaultErrorView"> <value>/common/error.jsp</value> </property> <property name="exceptionMappings"> <props> <prop key="java.lang.Exception">/common/error.jsp</prop> </props> </property> </bean>

下面我们来看看CustomSimpleMappingExceptionResolver.java是如何做到支持JSP和JSON格式返回的异常错误的

@Override protected ModelAndView doResolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) { // Expose ModelAndView for chosen error view. String viewName = determineViewName(ex, request); if (viewName != null) {//JSP格式返回 if(!(request.getHeader("accept").indexOf("application/json")>-1 || request.getHeader("X-Requested-With").indexOf("XMLHttpRequest")>-1)){//如果不是异步请求 // Apply HTTP status code for error views, if specified. // Only apply it if we're processing a top-level request. Integer statusCode = determineStatusCode(request, viewName); if (statusCode != null) { applyStatusCodeIfPossible(request, response, statusCode); return getModelAndView(viewName, ex, request); } }else{//JSON格式返回 Map<String, Object> model=new HashMap<String, Object>(); if(this.logger.isDebugEnabled()){ model.put("debug", true); }//exception model.put(ConfigConstants.RESULT, ex.getMessage()); model.put("failure", true); try { response.getWriter().write("有异常啦!"); } catch (IOException e) { e.printStackTrace(); } return new ModelAndView(); } return null; } else { return null; } }

这里判断了request.getHeader("accept").indexOf("application/json")是不是异步请求

下面给出同步和异步请求的Header

同步的text/html

=== MimeHeaders ===
host = localhost:8888
user-agent = Mozilla/5.0 (Windows; U; Windows NT 6.1; en-GB; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8
accept = text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
accept-language = en,zh;q=0.7,en-gb;q=0.3
accept-encoding = gzip,deflate
accept-charset = ISO-8859-1,utf-8;q=0.7,*;q=0.7
keep-alive = 115
connection = keep-alive
cookie = JSESSIONID=BB7441E4B481FF64A5BCC8E6F596C330

异步的application/json
=== MimeHeaders ===
host = localhost:8888
user-agent = Mozilla/5.0 (Windows; U; Windows NT 6.1; en-GB; rv:1.9.2.8) Gecko/20100722 Firefox/3.6.8
accept = application/json, text/javascript, */*
accept-language = en,zh;q=0.7,en-gb;q=0.3
accept-encoding = gzip,deflate
accept-charset = ISO-8859-1,utf-8;q=0.7,*;q=0.7
keep-alive = 115
connection = keep-alive
content-type = application/x-www-form-urlencoded
x-requested-with = XMLHttpRequest
referer = http://localhost:8888/auth/auth/dictionary/dictionaryForm.html
cookie = JSESSIONID=A4B59EA87C9B83B71C0D455634746411

请注意

try {
response.getWriter().write("有异常啦!");
} catch (IOException e) {
e.printStackTrace();
}
return new ModelAndView();

关键就在最后这1句 return new ModelAndView();

为什么不写 return null; 或者 return new ModelAndView('jsonView', model); 呢？

因为spring3的源码里这样写着了

protected ModelAndView processHandlerException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { // Check registerer 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; } 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; }

注意看

if (exMv != null) {
if (exMv.isEmpty()) {
return null;
}

这句和最后一句： throw ex;

如果你写 respone.getWriter().write("有异常啦"); 你也要 new一个空的ModelAndView，

上面的代码表明， 如果你 return null; 它就跑出异常 throw ex; 如果没人接收， 则会调用你配置的默认异常处理器

或者中断不做任何输出。

好了， 这样可以同时支持同步和AJAX异步请求异常处理了。

下面附上截图， 以免误人子弟~