https://issues.apache.org/bugzilla/show_bug.cgi?id=48582
Summary: JspServletWrapper.getServletContext() throws
NullPointerException
Product: Tomcat 6
Version: 6.0.20
Platform: PC
OS/Version: Linux
Status: NEW
Severity: major
Priority: P2
Component: Jasper
AssignedTo: dev@tomcat.apache.org
ReportedBy: tmcc...@yahoo-inc.com
We're getting this exception/stack trace in a web application:
''[2010-01-15 17:52:01,381] - ERROR [org.apache.catalina.core.ContainerBase]
Exception invoking periodic operation:
'java.lang.NullPointerException
at
org.apache.jasper.servlet.JspServletWrapper.getServletContext(JspServletWrapper.java:174)
at
org.apache.jasper.compiler.JspRuntimeContext.checkCompile(JspRuntimeContext.java:304)
at
org.apache.jasper.servlet.JspServlet.periodicEvent(JspServlet.java:289)
at
org.apache.catalina.core.StandardWrapper.backgroundProcess(StandardWrapper.java:668)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1571)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1580)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1580)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1580)
at
org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1560)
at java.lang.Thread.run(Thread.java:595)
Looking at JspServletWrapper, I see that it has 2 constructors; one for JSP
pages, and another for tag files. The one for tag files has a problem in this
line:
this.config = null; // not used
because this.config is indeed used by the public method getServletContext():
public ServletContext getServletContext() {
return config.getServletContext();
}
and since that method is public, you can't safely say that this.config will not
be used. :) So this means that if you create a JspServletWrapper for a JSP tag
file, you can never call getServletContext() on it, or you'll generate the NPE
above. However, JspRuntimeContext does exactly that in the following block of
code, from the checkCompile() method:
Object [] wrappers = jsps.values().toArray();
for (int i = 0; i < wrappers.length; i++ ) {
JspServletWrapper jsw = (JspServletWrapper)wrappers[i];
JspCompilationContext ctxt = jsw.getJspEngineContext();
// JspServletWrapper also synchronizes on this when
// it detects it has to do a reload
synchronized(jsw) {
try {
ctxt.compile();
} catch (FileNotFoundException ex) {
ctxt.incrementRemoved();
} catch (Throwable t) {
jsw.getServletContext().log("Background compile failed",
t);
}
}
}
The values in the "jsps" map are both JSP files and tag files, as seen by
TagFileProcessor.loadTagFile(), which puts tag files there.
So to summarize, any JSP tag file that experiences a compilation failure inside
of the checkCompile() method will seem to generate this NullPointerException.
A secondary issue here is that if any problem occurs inside of the catch block
in the code pasted above (as is currently happening), the original exception is
swallowed forever. This is the Throw From Within Finally anti-pattern
(http://today.java.net/article/2006/04/04/exception-handling-antipatterns#throwFromWithinFinally)
and should be fixed as well.
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