The only thing different here is the initial setup, you need to provide a list of jars from your WEB-INF/lib as well as the path to WEB-INF/classes since these aren't on the default java.class.path.

There are two ways to get this to work:

Way 1: Pass in the class names for all your entities

The advantage to this is that you don't need the ServletContext or anything, just the one method:

entityManagerFactory = EntityManagerFactoryEntityManagerFactoryImpl.newInstanceWithClassNames(persistenceUnitName, null, setOfClassName);

Way 2: Add Extra Webapp Class Paths

The advantage to this one is that you don't need to let SimpleJPA know about new entities or anything, it will just automagically find them.

This method will get you all the paths you need.

    private static Set<String> getLibPaths(ServletContext servletContext) {
        String basePath = servletContext.getRealPath("");
        Set<String> libPathsLocked = servletContext.getResourcePaths("/WEB-INF/lib");
        Set<String> libPaths = new HashSet<String>();
        if(libPathsLocked != null){
            for (String s : libPathsLocked) {
                // need to prefix with full path
                libPaths.add(basePath + s);
            }
        }
        String path = servletContext.getRealPath("/WEB-INF/classes");
        if (path != null) {
            File fp = new File(path);
            if (fp.exists()) libPaths.add(path);
        }
        return libPaths;
    }

This isn't in the SimpleJPA package because it adds a dependency on the servlet api.

Now all you need to do is create your EntityManagerFactory with the following constructor:

entityManagerFactory = new EntityManagerFactoryImpl(persistenceUnitName, null, libPaths);

TODO: Explain SimpleJPAUtil usage.