CODEWITHSUNDEEP
javajspservletstomcat7classloader
user2084865
user2084865

Reputation: 697

How do I set or access JspCompilationContext in Tomcat from a servlet?

I have a plugin system realized in Tomcat 7 which loads dynamically classes of these plugins (reloadable via a custom classloader). Unfortunately, if a plugin has a JSP which uses a class which belongs to this plugin, it cannot find this class. This seems to be the correct behavior as we have the Tomcat classloader hierarchy and my custom classloader is at the bottom.

Nevertheless, with this hacky thing I can make the classes available to the JSPs:

        URLClassLoader webappClassloader = (URLClassLoader)Thread.currentThread().getContextClassLoader();
        Method addURLMethod = webappClassloader.getClass().getDeclaredMethod("addURL", URL.class);
        addURLMethod.setAccessible(true);
        for(String url : pluginFolders)
            addURLMethod.invoke(webappClassloader, new URL("file://" + url));

Please note, that the plugins are not in the WEB-INF/classes directory.

This is all great but now a class can only be loaded once (see also this). In order to make the plugins updatable (without restarting the whole webapp) I am using a custom classloader. But I wasn't able to set this classloader to be used by Jasper (I tried Thread.currentThread().setContextClassLoader() which had no effect). I digged into the source of Jasper and it seems like it should be possible to set a custom classloader. But I have no idea how to achieve this from a servlet.

Maybe you can give me an answer to one of the following questions?

Thanks in advance!

Upvotes: 2

Views: 107

Answers (1)

Christopher Schultz
Christopher Schultz

Reputation: 20862

You need to set your own ClassLoader using the for the <Context> in META-INF/context.xml. This will allow you to specify the ClassLoader that will be used for your web application.

Upvotes: 2

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