The packaging scheme for Tuscany runtime and dependency jars is problematic
against the Tomcat class loading hierarchy
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Key: TUSCANY-262
URL: http://issues.apache.org/jira/browse/TUSCANY-262
Project: Tuscany
Type: Bug
Components: Java SCA Tomcat Integration
Reporter: Raymond Feng
Priority: Critical
As a result from the investigation on JIRA issue Tuscany-258, I found the
following problem.
Right now, most of the Tuscany and dependency jars are copied to
$CATALINA_HOME/server/lib. Is it by design? I think it's problematic and it's
the root cause of the problem
described by 258.
Here's a quote from the Tomcat 5.0 document @
http://tomcat.apache.org/tomcat-5.0-doc/class-loader-howto.html:
"Catalina - This class loader is initialized to include all classes and
resources required to implement Tomcat 5 itself. These classes and resources
are TOTALLY invisible to web applications. All unpacked classes and resources
in $CATALINA_HOME/server/classes, as well as classes and resources in JAR files
under $CATALINA_HOME/server/lib, are made visible through this class loader. "
It leads to a very messy classloading story. The classloader for the Tuscany
runtime classes/interfaces is NOT part of the web application's classloader
chain. Some classes in the runtime (including Tuscany and Axis2) uses Thread
context classloader as the starting point to resolve resources/classes and
it'll fail without the hacky classloader switching all over the place.
I did some experiement and found out the following should be the correct
packaging scheme:
1) Only tuscany-tomcat-SNAPSHOT.jar should be copied to
$CATALINA_HOME/server/lib since it contains a class
"org.apache.tuscany.tomcat.TuscanyHost" extending
"org.apache.catalina.core.StandardHost" which is packaged in catalina.jar under
$CATALINA_HOME/server/lib.
2) All the other Tuscany jars should be copied to $CATALINA_HOME/common/lib
With the new strategy, we can remove the classloader switching hacks in the
code base.
I can upload the patch if you guys agree with me. The patch includes the
changes against the build.xml (testing/tomcat), TuscanyContextListener.java
(sca/tomcat) and the rollbacks of the workaround committed by Ant under 258.
Thanks,
Raymond
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