关于java.lang.NullPointerException: Module 'null' not found.的问题

在用eclipse做struts1项目时，配置都ok了。可是一运行就报java.lang.NullPointerException: Module 'null' not found.错。

代码如下；

web.xml

 1 <servlet>
 2         <servlet-name>action</servlet-name>
 3         <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
 4         <init-param>
 5             <param-name>config</param-name>
 6             <param-value>/WEB-INF/struts-config.xml</param-value>
 7         </init-param>
 8     </servlet>
 9     <servlet-mapping>
10         <servlet-name>action</servlet-name>
11         <url-pattern>*.do</url-pattern>
12     </servlet-mapping>

struts-config.xml：

 1 <struts-config>
 2     <form-beans>
 3        <form-bean name="loginForm" type="com.actionform.LoginForm" />
 4     </form-beans>
 5     <action-mappings>
 6        <action path="/login" type="com.action.LoginAction" name="loginForm" input="/index.jsp"
 7            scope="request">
 8            <forward name="success" path="/success.jsp" />
 9        </action>
10     </action-mappings>
11 </struts-config>

jsp页面：

1 <html:form action="login.do" method="post">
2         <html:text property="username"></html:text>
3         <br> <html:submit value="Submit"></html:submit>
4 </html:form>

action和actionform都是ok的。

配置和好后，程序无任何语法异常。但是在我打开index.jsp页面的时候程序抛出了空指针异常

java.lang.NullPointerException: Module 'null' not found.抛出这个异常的时候我们知道这是由于Tomcat并未加载

ActionServlet 以致Jsp界面使用Struts中的<html:text property="">程序抛出异常.

 1 Oct 10, 2015 4:38:15 PM org.apache.catalina.core.StandardWrapperValve invoke
 2 SEVERE: Servlet.service() for servlet jsp threw exception
 3 java.lang.NullPointerException: Module 'null' not found.
 4     at org.apache.struts.taglib.TagUtils.getModuleConfig(TagUtils.java:755)
 5     at org.apache.struts.taglib.TagUtils.getModuleConfig(TagUtils.java:735)
 6     at org.apache.struts.taglib.html.FormTag.lookup(FormTag.java:818)
 7     at org.apache.struts.taglib.html.FormTag.doStartTag(FormTag.java:488)
 8     at org.apache.jsp.index_jsp._jspx_meth_html_005fform_005f0(index_jsp.java:83)
 9     at org.apache.jsp.index_jsp._jspService(index_jsp.java:54)
10     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
11     at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
12     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
13     at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
14     at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
15     at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
16     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
17     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
18     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
19     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
20     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
21     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
22     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
23     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
24     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:874)
25     at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
26     at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
27     at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
28     at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:689)
29     at java.lang.Thread.run(Unknown Source)

异常延伸：

     一、这个异常就牵扯到web.xml  的<load-on-startup></load-on-startp>

 

     二、那么这个标签有什么用了？

这个标签有着很重要的用途<load-on-startup>（在这里可以放置0-5之间的整数）</load-on-startp>

 

1 <servlet>
2         <servlet-name>action</servlet-name>
3         <servlet-class>org.apache.struts.action.ActionServlet</servlet-class>
4         <init-param>
5             <param-name>config</param-name>
6             <param-value>/WEB-INF/struts-config.xml</param-value>
7         </init-param>
8         <load-on-startup>1</load-on-startup>
9     </servlet>

 

     三、0-5 是web容器控制Tomcat告诉Tomcat按怎样的顺序去执行init（）方法加载Servlet（程序中可能会有多个Serlvet)如果没有在web.xml中使用这个标签或者参数的为负数 那么Tomcat将不自动加载这个Servlet。上诉错误就是因

为没有在web.xml中配置<load-on-startup>标签

 

    四、另外<load-on-startup>中的参数越小那么优先级也就越高

 

posted @ 2015-10-10 16:41  权杖攻城狮  阅读(1204)  评论(0)  编辑  收藏  举报