Is there any way I can assign different values of CLASSPATH to different contexts?

One way to get the functional equivalent is to put the files in question in either "<app-path>/WEB-INF/classes" or "<app-path>/WEB-INF/lib", depending on whether you are talking about a .class or .jar. The CLASSPATH for a given webapp will include WEB-INF/classes and all the .jar files found in WEB-INF/lib. Say you had utils.jar and form-taglib.jar in WEB-INF/lib, the resulting classpath would look like:

  $CLASSPATH:<app-path>/WEB-INF/classes:<app-path>/WEB-INF/lib/utils.jar:<app-path>/WEB-INF/lib/form-taglib.jar