We are using jboss4.0.4GA with jboss default configuration. We made following changes in $JBOSS_HOME/server/default/deploy/jbossweb-tomcat55.sar/META-INF/jboss-service.xml
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
<!-- Get the flag indicating if the normal Java2 parent first class
loading model should be used over the servlet 2.3 web container first
model.
-->
false
<!-- A flag indicating if the JBoss Loader should be used. This loader
uses a unified class loader as the class loader rather than the tomcat
specific class loader.
The default is false to ensure that wars have isolated class loading
for duplicate jars and jsp files.
-->
false
<!-- The list of package names that should not be loaded without
delegating to the parent class loader before trying the web app
class loader. The packages listed here are those tha are used by
the web container implementation and cannot be overriden.
This only applies when UseJBossWebLoader=false.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Somehow, when Jboss starts, we always get following error:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
at org.jboss.mx.loading.RepositoryClassLoader.loadClassLocally(RepositoryClassLoader.java:190)
at org.jboss.mx.loading.UnifiedLoaderRepository3.loadClassFromClassLoader(UnifiedLoaderRepository3.java:277)
at org.jboss.mx.loading.LoadMgr3.beginLoadTask(LoadMgr3.java:189)
at org.jboss.mx.loading.RepositoryClassLoader.loadClassImpl(RepositoryClassLoader.java:511)
at org.jboss.mx.loading.RepositoryClassLoader.loadClass(RepositoryClassLoader.java:405)
at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at org.jboss.ws.server.WebServiceDeployerJSE.isWebserviceDeployment(WebServiceDeployerJSE.java:151)
at org.jboss.ws.server.WebServiceDeployer.create(WebServiceDeployer.java:101)
at org.jboss.ws.server.WebServiceDeployerJSE.create(WebServiceDeployerJSE.java:66)
at org.jboss.deployment.SubDeployerInterceptorSupport$XMBeanInterceptor.create(SubDeployerInterceptorSupport.java:180)
at org.jboss.deployment.SubDeployerInterceptor.invoke(SubDeployerInterceptor.java:91)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

It is too weird, we have javax.servlet.jar at $JBOSS_HOME/server/lib/

It seems that tomcat class loader can't have jars from jboss system class repository.

Any input would be greatly appreciated. Thanks in advance.