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~