Tomcat 6 server - was running, but now it won't start - error in log file -SEVERE: Null component?

java tomcat startup catalina.out
katura picture katura · Dec 3, 2010 · Viewed 7.3k times · Source

I've been running Tomcat 6 on my pc for some time now, and it has been running successfully...up until today. I just tried to start it, and now for some reason it won't start.

I start it from a command line prompt. The second prompt that appears after I enter 'startup' in the first prompt is exiting quickly, whereas it usually stays open and shows the status of the server.

Here's what the log file logged -

Dec 3, 2010 4:00:00 PM org.apache.catalina.core.AprLifecycleListener init
INFO: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\Java\jdk1.5.0_16\bin;.;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\system32\WindowsPowerShell\v1.0;c:\Program Files\Common Files\Roxio Shared\DLLShared\;C:\Java\jdk1.5.0_16\bin;C:\jakarta-tomcat\bin;C:\MYSQL\MySQL Server 5.1\bin
Dec 3, 2010 4:00:01 PM org.apache.coyote.http11.Http11Protocol init
INFO: Initializing Coyote HTTP/1.1 on http-8080
Dec 3, 2010 4:00:01 PM org.apache.catalina.startup.Catalina load
INFO: Initialization processed in 424 ms
Dec 3, 2010 4:00:01 PM org.apache.catalina.core.StandardService start
INFO: Starting service Catalina
Dec 3, 2010 4:00:01 PM org.apache.catalina.core.StandardEngine start
INFO: Starting Servlet Engine: Apache Tomcat/6.0.29
Dec 3, 2010 4:00:01 PM org.apache.tomcat.util.modeler.Registry registerComponent
SEVERE: Null component Catalina:type=JspMonitor,name=jsp,WebModule=//localhost/MyWebApp,J2EEApplication=none,J2EEServer=none

I never saw this before, where it says SEVERE: Null component... - what does it mean? What's causing it?

Answer

katura picture katura · Dec 6, 2010

Here's what I ended up doing. I made a backup of my server.xml and web.xml files, along with my apps under the webapps folder, and removed jakarta-tomcat, and then reinstalled it. I restored the server.xml and web.xml file, threw my webapps back in, and started Tomcat up. This time, I got the same error as before, but it pinpointed that a particular servlet under one of my folders had a "bad version number". So I went through my servlet folders and recompiled the classes.

I started Tomcat again, and its running as it used to.

The problem was that a class had been compiled under a different version of the JDK, and it was causing an error.

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