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From "Reich, Matthias" <>
Subject RE: axis - tomcat "loader constraint violation"
Date Fri, 13 Jul 2007 12:54:46 GMT

it looks as if class


was as well found in common/lib as in the WEB-INF/lib folder of your

If the webapp classloader looks for this class, it will first look in
webapps private resources.
However, the class had been loaded and resolved before via the common
classloader when some other class had referred to it.
If javax/xml/rpc/Service would not be accessible via the webapp's
private resources,
the webapp classloader would delegate the task of loading the class to
it's parent classloader,
an then no conflict would arise.

You should take care to have classes located *either* in the common
classpath *or* in the webapp classpath, but not in both of them.


> -----Original Message-----
> From: E Koutsoudaki [] 
> Sent: Friday, July 13, 2007 2:12 PM
> To:
> Subject: axis - tomcat "loader constraint violation"
> Dear all,
> as part of a project I am working on I have to add to an 
> existent Java 
> based web
> application the functionality of retrieving information from the NCBI 
> web service.
> I have generated the Java source files by following the 
> instructions in 
> the NCBI website
> at:
> The source files are created and they compile. For testing reasons I 
> have implement a
> Java application (not web based) from which I was able to retrieve 
> information from the
> NCBI resources.
> When integrate the source files into the web based application, again 
> the project builds
> fine, but when running the following error occurs:
> java.lang.LinkageError: loader constraint violation: when resolving 
> field "service" the
> class loader (instance of 
> org/apache/catalina/loader/WebappClassLoader) 
> of the referring
> class, org/apache/axis/client/Stub, and the class loader (instance of
> org/apache/catalina/loader/StandardClassLoader) for the 
> field's resolved type,
> javax/xml/rpc/Service, have different Class objects for that type
> gov.nih.nlm.ncbi.www.soap.eutils.EUtilsServiceSoap
> Stub.<init>(
> gov.nih.nlm.ncbi.www.soap.eutils.EUtilsServiceSoap
> Stub.<init>(
> gov.nih.nlm.ncbi.http://www.soap.eutils.EUtilsService...ocator
> .java:55)
> gov.nih.nlm.ncbi.http://www.soap.eutils.EUtilsService...ocator
> .java:50)
> The web based application runs on a Tomcat server and the 
> axis library 
> files have been
> added in the common/lib folder of the web server so as the web server 
> to be able to
> locate the libraries.
> The axis version I've used is the 1.4, Tomcat 5.5 and jdk 1.6.0_01.
> I have also tried by using the axis-1_2_1, and jdk1.5.0_12. and 
> generally other
> combinations of those. I always keep Tomcat to 5.5 since this is the 
> version of the
> existing web application.
> I would be grateful for any enlightenment about the occurring error.
> Thank you in advance.
> Elisavet Koutsoudaki
> ---------------------------------------------------------------------
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