SecurityException - Class signer ?

Question

I'm trying to learn to use JAXB..
Well.. the XML schema binding and stuff seems to go well, but when i try to use the classes (only trying to instantiate the "main" object of my XML structure), i get the following exception :
java.lang.SecurityException: class "javax.xml.namespace.NamespaceContext"'s signer information does not match signer information of other classes in the same package
I read some posts on the forums and some people (with a 'signer-problem') said that there's probably two different versions of the class that's causing the exception on the classpath..
One NamespaceContext -class seems to be in the namespaces.jar that comes with the Java Web Services Development Pack, but where is the other ?
And even if i knew where both of them are (if that's even the problem), what could i do about it ? I probably can't change the system libraries ? :)
This has been driving me nuts all day long, but i'd like to get JAXB to work, so maybe you could help me out here?
Maybe i messed something up while clicking on "next" during the installation process ? :)
And no one else seemed to have had any trouble with the NamespaceContext class !

Answer 1

I had the same issue trying to deploy JAXB 1.3 with WebSphere 5.1.
The problem in this case was that webservices.jar dynamically load qname.jar which contains classes in the package javax.xml.namespace. namespace.jar also contains classes in this package but the signer is different hence the exception. All I had to do to fix it was put webservices.jar after namespace.jar in the classpath. Also wrote this code to report something useful to people trying to deploy the code.
    private static String getUsefulMsg (String msg, Throwable exc)
        Throwable t = exc;
        String retMsg = msg;
        while (t != null)
            if (SecurityException.class.isAssignableFrom(t.getClass()))
                // This happens because webservices.jar dynamically loads qname.jar which has
                // classes in the same package as namespace.jar but with a different signer.
                if (t.getMessage().equals(UNHELPFUL_MESSAGE))
                    // explain how to fix this setup problem
                    retMsg = HELPFUL_MESSAGE;
                break;
            else if (t.getClass().isAssignableFrom(JAXBException.class))
                t = ((JAXBException)t).getLinkedException();
            else
                break;
        return retMsg;
    private static final String HELPFUL_MESSAGE = "webservices.jar needs to be after namespace.jar in classpath";
    private static final String UNHELPFUL_MESSAGE =  "class  \"javax.xml.namespace.NamespaceContext\"'s signer information does not match signer information of other classes in the same package";