Servlet中的JNDI查找会导致permgen内存泄漏吗？

Question

Since JBoss 4.2 does not support @EJB injections, I am using a JNDI lookup to reference an EJB that is needed by a Servlet.

I am concerned that this type of lookup may be causing the Permgen non-heap memory in the JVM to grow.

As I understand JNDI, it is a form of dynamic classloading, so this might be causing a classloader leak.

So my question is, could the below servlet code possibly be causing a Permgen memory leak over time?

Also, should I be explicitly calling the close() method on InitialContext after the lookup? Is there a chance that GC is not cleaning up the InitialContexts as expected due to the way they are being instantiated here (in a Servlet)?

Thank you.

public class MyServlet extends HttpServlet {

// JBoss 4.x does not support @EJB injections in servlets (see jndi lookup below)
@EJB
private MyService myService;

private static final String SERVICE_JNDI_NAME = "MyServiceBean";

private Logger log = Logger.getLogger(this.getClass().getPackage().getName());


public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

try {
    // JBoss 4.x does not support @EJB injections in servlets
    InitialContext ctx = new javax.naming.InitialContext();
    myService = (MyService) ctx.lookup(SERVICE_JNDI_NAME);
} catch (NamingException e) {
    log.warn("NamingException trying to lookup MyService in context");
    throw new RuntimeException(e);
}

...

RequestDispatcher requestDispatcher = request.getRequestDispatcher("/page.jsp");
requestDispatcher.forward(request, response);
}

}

Answer 1

JNDI is a directory lookup service and a core technology of Java Enterprise Edition application servers. Unless you have a buggy implementation or have an application with an unusual usage pattern, then I would expect the classes loaded because of JNDI to stabilize eventually.

Either way, I strongly recommend you to use a heap dump analyzer . Take several snapshots while your application is running and see what is added when the permgen keeps increasing. This information will either show you directly what the problem is, or help narrow down the root cause to a much smaller area.