[PATCH] Fix:
java.lang.NullPointerException
	at org.apache.jasper.compiler.TagLibraryInfoImpl.toString(TagLibraryInfoImpl.java:129)\
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Ref: https://issues.apache.org/jira/browse/WW-4223
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Yasser Zamani added a comment - 21/Oct/13 09:36
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I discovered the source of the problem. It seems that there is no problem with Struts itself but when you run a Struts application on:
    Jetty: TagLibraryInfoImpl class will be resolved from jetty home/lib/jsp/org.apache.jasper.glassfish-2.2.2.v201112011158.jar where line #129 is:
        TagLibraryInfoImpl.java:129
            print("tagLibraryValidator", tagLibraryValidator.toString(), out);
but in
    Tomcat: TagLibraryInfoImpl class will be resolved from tomcat home/lib/jasper.jar where equivalent code at line #94 is:
        TagLibraryInfoImpl.java:94
            print("tagLibraryValidator", "" + tagLibraryValidator, out);
These facts show that when tagLibraryValidator is null, Jetty will be broken by NPE (because of tagLibraryValidator.toString()) but Tomcat continues well (because of "" + tagLibraryValidator).