Velocity behavior explained?

From: Christian Mittendorf (christian.mittendor..reenet.de)
Date: Thu Aug 11 2005 - 05:02:30 EDT

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    Hello!

    We experienced a problem with Cayenne and multiple data nodes.

    I will describe our setup first: we run multiple webapps on a tomcat.
    The cayenne.xml
    is stored in the shared directory, most of the third party jars are
    also located there.
    Cayenne-nodeps.jar is always part of each webapp.

    The setup was working fine until we added 2 more data nodes to
    cayenne.xml. We were then
    running into a problem that we cannot access the two new nodes, but
    we could still use our
    first node.

    In catalina.out we saw the following error:

    SEVERE: Servlet.service() for servlet pos threw exception
    java.lang.ExceptionInInitializerError
             at
    org.objectstyle.cayenne.access.jdbc.SQLTemplateSelectExecutionPlan.execu
    te(SQLTemplateSelectExecutionPlan.java:97)
             at org.objectstyle.cayenne.access.DataNode.performQueries
    (DataNode.java:341)
             at org.objectstyle.cayenne.access.DataDomain.performQueries
    (DataDomain.java:654)
    [...]
    Caused by: org.objectstyle.cayenne.CayenneRuntimeException: [v.1.1B2
    July 25 2004] Error setting up Velocity RuntimeInstance.
             at
    org.objectstyle.cayenne.access.jdbc.SQLTemplateProcessor.initVelocityRun
    time(SQLTemplateProcessor.java:119)
             at
    org.objectstyle.cayenne.access.jdbc.SQLTemplateProcessor.<clinit>
    (SQLTemplateProcessor.java:96)
             ... 30 more
    Caused by: java.lang.Exception: The specified class for
    Resourcemanager
    (org.objectstyle.cayenne.access.jdbc.SQLTemplateResourceManager) does
    not ex
    ist (or is not accessible to the current classlaoder.
             at
    org.apache.velocity.runtime.RuntimeInstance.initializeResourceManager
    (RuntimeInstance.java:506)
             at org.apache.velocity.runtime.RuntimeInstance.init
    (RuntimeInstance.java:227)
             at
    org.objectstyle.cayenne.access.jdbc.SQLTemplateProcessor.initVelocityRun
    time(SQLTemplateProcessor.java:116)
             ... 31 more

    Changing our setup and moving velocity.jar into each webapp did solve
    the problem.

    However, we would now like to understand it. What is the reason for
    this behaviour?

    Christian

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