关于tiles，Tomcat报错，该怎么解决啊？

Question

严重: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.struts.taglib.tiles.InsertTag.processAttribute(InsertTag.java:687)
at org.apache.struts.taglib.tiles.InsertTag.createTagHandler(InsertTag.java:478)
at org.apache.struts.taglib.tiles.InsertTag.doStartTag(InsertTag.java:438)
at org.apache.jsp.layout_jsp._jspx_meth_tiles_005finsert_005f0(layout_jsp.java:126)
at org.apache.jsp.layout_jsp._jspService(layout_jsp.java:68)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
问题该怎么解决啊？？急！！

Answer 1

java.lang.NullPointerException 
空异常了at org.apache.jsp.layout_jsp._jspx_meth_tiles_005finsert_005f0(layout_jsp.java:126)
at org.apache.jsp.layout_jsp._jspService(layout_jsp.java:68) 这个根据信息提示，跟踪下程序流程。。

Answer 2

标签用的有问题，用的时候有的 值为NULL.,,

Answer 3

问题解决了，是struts-config.xml配置没写好，原先是这样写的：
<action
      parameter="index-definition"
      path="/index"
      type="com.yourcompany.struts.action.IndexAction">
      <forward name="success" path="/layout.jsp" />
</action>
修改了，path="index-definition"后就正常显示了。还是没仔细看书，没完全理解就敲例子代码，心急吃不了热豆腐啊，╮(╯▽╰)╭