Why did Servlet.service() for servlet jsp throw this exception?

Question

I get the following error, what could be the problem?

My context descriptor:

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">    <servlet>     <servlet-name>UploadServlet</servlet-name>     <servlet-class>controller.UploadServlet</servlet-class>   </servlet>    <servlet-mapping>     <servlet-name>UploadServlet</servlet-name>     <url-pattern>/UploadServlet</url-pattern>   </servlet-mapping>   <welcome-file-list>     <welcome-file>index.jsp</welcome-file>   </welcome-file-list> </web-app> 

SEVERE: Servlet.service() for servlet jsp threw exception java.lang.NullPointerException     at org.apache.jsp.index_jsp._jspInit(index_jsp.java:22)     at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52)     at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:159)     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)     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:293)     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)     at java.lang.Thread.run(Unknown Source) Feb 23, 2010 11:35:28 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet jsp threw exception java.lang.NullPointerException     at org.apache.jsp.index_jsp._jspInit(index_jsp.java:22)     at org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52)     at org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:159)     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)     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:293)     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)     at java.lang.Thread.run(Unknown Source) 

Answer 1

It can be caused by a classpath contamination. Check that you /WEB-INF/lib doesn't contain something like jsp-api-*.jar.