[Bug 58701] New: JSP Reloading Initialization Problem

[bu...@apache.org]

https://bz.apache.org/bugzilla/show_bug.cgi?id=58701

            Bug ID: 58701
           Summary: JSP Reloading Initialization Problem
           Product: Tomcat 8
           Version: 8.0.29
          Hardware: PC
                OS: Mac OS X 10.1
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Catalina
          Assignee: dev@tomcat.apache.org
          Reporter: l2.rowlands@gmail.com

Created attachment 33332
  --> https://bz.apache.org/bugzilla/attachment.cgi?id=33332&action=edit
The logs for the tomcat reloading bug.

My company uses a custom inhouse tomcat library for hotloading generated source
into tomcat at runtime. This custom classloader requires tomcat's JSP engine to
perform a reload, so that it can recognize the newly generated classes. We are
performing the following code to facilitate this:


    Context context = this.getContext();
    Wrapper jspWrapper = (Wrapper)context.findChild("jsp");

    // There might not be any jsps if we're just getting started.
    if (jspWrapper==null) return;

    jspWrapper.unload();
    jspWrapper.load();


This code works just fine on Tomcat 6. However, when migrating this custom
classloader to Tomcat 8, a subsequent JSP page load fails with the attached
stacktrace.

I have investigated this stack trace and come to the conclusion that, in
StandardWrapper.java on line 1473, although the instance itself is set to null,
the field "instanceInitialized" is still set to true. This means that my next
call to load will recreate the JspServlet, but it will not be initialized
correctly, thus causing the error in the attached stacktrace. I have seen in
the debugger that it is indeed the case that the JspServlet is not being
initialized properly.

A fix for this bug is to simply add this line:

instanceInitialized = false;

to line 1474 in StandardWrapper.java.

I have successfully been able to work around this bug in my own code with the
following hack:

    Context context = this.getContext();
    Wrapper jspWrapper = (Wrapper)context.findChild("jsp");

    // There might not be any jsps if we're just getting started.
    if (jspWrapper==null) return;

    jspWrapper.unload();

    // tomcat-catalina 8.0.29
    // This custom hack is required to fix a bug in the StandardWrapper
catalina sourcecode. This custom field in their source was not reset back to
false
    // after calling unload, so the underlying JspServlet (the instance) did
not get initialized properly upon calling load.
    // This bug happens in tomcat 7 and 8.
    AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
      public Boolean run() {
        try
        {
          Field field =
((StandardWrapper)jspWrapper).getClass().getDeclaredField("instanceInitialized");
          field.setAccessible(true);
          field.setBoolean(jspWrapper, false);
        }
        catch (NoSuchFieldException | SecurityException |
IllegalArgumentException | IllegalAccessException e)
        {
          throw new RuntimeException(e);
        }

        return Boolean.TRUE;
      }
    });


    jspWrapper.load();

Although as you can see it is far from ideal.

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[Bug 58701] JSP Reloading Initialization Problem

[bu...@apache.org]

https://bz.apache.org/bugzilla/show_bug.cgi?id=58701

Mark Thomas <ma...@apache.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from Mark Thomas <ma...@apache.org> ---
Thanks for the report and the analysis.

I have fixed the issue along with some other issues in StandardWrapper in 9.0.x
for 9.0.0.M2 onwards, 8.0.x for 8.0.31 onwards and 7.0.x for 7.0.68 onwards.

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