Java EE (Java Enterprise Edition) General Discussion

I'm having a problem with a custom tag class, and I'm not sure whether it's because I'm doing something wrong, or because I'm running into a bug with Tomcat, JDK1.4b2, or something else. Basically, I'm finding that the pageContext object is null in the constructor of a custom tag class... something that I'm pretty sure is NOT supposed to happen.

I'm running JDK1.4b2 with Forte CE 3.1 (the bug predates the jumbo fix that brought it up to 3.0) and using Forte's embedded Tomcat.

I'm not sure whether it matters, but here's the sequence of events:

A servlet gets launched,
instantiates an object of type Error_list,
binds Error_list to the request object, and
forwards to a JSP that uses the custom tag defined by ListErrorsTag.
Unfortunately, pageContext is null in ErrorListTag's constructor, so the attempt to get the request object from the pageContext object generates a NullPointerException.

The SERVLET: *****************************************
// relevant lines from the servlet instantiating the object, binding it, and forwarding...

     Error_list errors = new Error_list("BAD_THINGS", "crash and burn");
     request.setAttribute("errors",errors);

     ServletContext sc = this.getServletContext();
     RequestDispatcher rd = sc.getRequestDispatcher("admin_category_create.jsp");
     rd.forward(request,response);

The JSP: ************************************************
In the JSP "admin_category_create.jsp" itself, I specify the taglib:

     
     <%@ taglib uri='/WEB-INF/AdminTags.tld' prefix = 'admin' %>

and reference it:

     <admin:listErrors>The errors will be listed here</admin:listErrors>

The Explosion of the Taglib: ************************
// beginning of Taglib class:

public class ListErrorsTag extends BodyTagSupport {
    
    private Error_list errors;
    
    public ListErrorsTag() {
    super()
    
    try {
    
         if (pageContext == null)
             System.out.println("uh oh! pageContext is null");
         
         ServletRequest request = pageContext.getRequest();
         
         errors = (Error_list)request.getAttribute("errors");
    
    }
    catch (NullPointerException e) {
         System.out.println("boom!");
    }
}

The Result: **************************************

Tomcat's error log:

uh oh! pageContext is null
boom!

*************************************
if I eliminate the try/catch and allow the NullPointerException to take place, I get:

Error: 500
Location: /admin_category_create.jsp
Internal Servlet Error:

javax.servlet.ServletException
at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:459)
at _0002fadmin_0005fcategory_0005fcreate_0002ejspadmin_0005fcategory_0005fcreate_jsp_0._jspService(_0002fadmin_0005fcategory_0005fcreate_0002ejspadmin_0005fcategory_0005fcreate_jsp_0.java:338)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:177)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:318)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:391)
at org.netbeans.modules.web.tomcat.JspServlet.service(JspServlet.java:91)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
at org.apache.tomcat.core.Handler.service(Handler.java:286)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.facade.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:194)
at admin.processRequest(admin.java:126)
at admin.doPost(admin.java:144)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
at org.apache.tomcat.core.Handler.service(Handler.java:286)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:797)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:210)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:498)
at java.lang.Thread.run(Thread.java:539)

Root cause:
java.lang.NullPointerException
at AdminTags.ListErrorsTag.(ListErrorsTag.java:32)
at _0002fadmin_0005fcategory_0005fcreate_0002ejspadmin_0005fcategory_0005fcreate_jsp_0._jspService(_0002fadmin_0005fcategory_0005fcreate_0002ejspadmin_0005fcategory_0005fcreate_jsp_0.java:272)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:177)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:318)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:391)
at org.netbeans.modules.web.tomcat.JspServlet.service(JspServlet.java:91)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
at org.apache.tomcat.core.Handler.service(Handler.java:286)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.facade.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:194)
at admin.processRequest(admin.java:126)
at admin.doPost(admin.java:144)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.tomcat.core.ServletWrapper.doService(ServletWrapper.java:404)
at org.apache.tomcat.core.Handler.service(Handler.java:286)
at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372)
at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:797)
at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743)
at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:210)
at org.apache.tomcat.service.TcpWorkerThread.runIt(PoolTcpEndpoint.java:416)
at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(ThreadPool.java:498)
at java.lang.Thread.run(Thread.java:539)