文件上传时控制上传文件类型，单个文件大小时的问题

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: java.lang.NullPointerException
	org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515)
	org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)

root cause

java.lang.NullPointerException
	com.test.action.FileUploadAction.execute(FileUploadAction.java:79)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	java.lang.reflect.Method.invoke(Method.java:597)
	com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:404)
	com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:267)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:229)
	org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:268)
	com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
	com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
	com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
	com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
	org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:50)
	org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:504)
	org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.20 logs.

==============================================================================
struts.xml 配置文件 如下：

		<action name="uploadAction" class="com.test.action.FileUploadAction">
			<result name="success">/fileupload1/resultupload.jsp</result>
			<result name="file">/fileupload/fileupload.jsp</result>
			
			<interceptor-ref name="fileUpload">
				<!-- path: package org.apache.struts2.interceptor.FileUploadInterceptor	maximumSize		字節-->
				<param name="maximumSize">1024000</param>
				<!--	上传文件允许的类型 		-->
				<!--	C:\Program Files\Apache Software Foundation\Tomcat 6.0\conf\web.xml 参照		-->
				<param name="allowedTypes">image/jpeg</param>
			</interceptor-ref>
		
		</action>

==========================================
分析问题一旦一个Action中写了拦截器，那么默认的拦截器将不再被调用。
所以应该为：
==========================================

<action name="uploadAction" class="com.test.action.FileUploadAction">
			<result name="success">/fileupload/resultupload.jsp</result>
			<result name="input">/fileupload1/fileupload.jsp</result>
			
			<interceptor-ref name="fileUpload">
				<!-- path: package org.apache.struts2.interceptor.FileUploadInterceptor	maximumSize		字節-->
				<param name="maximumSize">1024000</param>
				<!--	上传文件允许的类型 		-->
				<!--	C:\Program Files\Apache Software Foundation\Tomcat 6.0\conf\web.xml 参照		-->
				<param name="allowedTypes">image/jpeg</param>
			</interceptor-ref>
			<interceptor-ref name="defaultStack">
			</interceptor-ref>
		</action>