FWD » Core Development

Today I added some new functionality to FWD and suddenly the client started to abend with

java.lang.NullPointerException
    at com.sun.proxy.$Proxy2.getSessionTooltips(Unknown Source)
    at com.goldencode.p2j.ui.chui.ThinClient.setSessionTooltips(ThinClient.java:3408)
    at com.goldencode.p2j.main.ClientCore.start(ClientCore.java:346)
    at com.goldencode.p2j.main.ClientCore.start(ClientCore.java:163)
    at com.goldencode.p2j.main.ClientDriver.start(ClientDriver.java:250)
    at com.goldencode.p2j.main.CommonDriver.process(CommonDriver.java:444)
    at com.goldencode.p2j.main.ClientDriver.process(ClientDriver.java:144)
    at com.goldencode.p2j.main.ClientDriver.main(ClientDriver.java:313)

This was quite known to me, but I did not exactly recalled why this happens. In fact, this NPE can be thrown because of a lot of factors because this is the first access to session internal data so all initializations occur here. I turned to server and investigated. I found the following hidden (I had to manually print it out because, by default is not displayed) exception:

java.lang.ExceptionInInitializerError
    at com.goldencode.p2j.util.HandleResource.<init>(HandleResource.java:136)
    at com.goldencode.p2j.util.HandleChain.<init>(HandleChain.java:225)
    at com.goldencode.p2j.util.HandleChain.<init>(HandleChain.java:198)
    at com.goldencode.p2j.util.HandleChain.<init>(HandleChain.java:185)
    at com.goldencode.p2j.ui.GenericWidget.<init>(GenericWidget.java:410)
    at com.goldencode.p2j.ui.BaseEntity.<init>(BaseEntity.java:225)
    at com.goldencode.p2j.ui.PaneEntity.<init>(PaneEntity.java:106)
    at com.goldencode.p2j.ui.WindowWidget.<init>(WindowWidget.java:197)
    at com.goldencode.p2j.ui.LogicalTerminal.init(LogicalTerminal.java:1255)
    at com.goldencode.p2j.security.ContextLocal.initializeValue(ContextLocal.java:655)
    at com.goldencode.p2j.security.ContextLocal.get(ContextLocal.java:494)
    at com.goldencode.p2j.security.ContextLocal.get(ContextLocal.java:430)
    at com.goldencode.p2j.ui.LogicalTerminal.locate(LogicalTerminal.java:11168)
    at com.goldencode.p2j.ui.LogicalTerminal.lambda$initialize$6(LogicalTerminal.java:12282)
    at com.goldencode.p2j.util.TransactionManager$ContextContainer.obtain(TransactionManager.java:10112)
    at com.goldencode.p2j.util.TransactionManager.isHeadless(TransactionManager.java:2549)
    at com.goldencode.p2j.util.ErrorManager$ServerDataAccess.isHeadless(ErrorManager.java:2705)
    at com.goldencode.p2j.util.ErrorManager.isHeadless(ErrorManager.java:2120)
    at com.goldencode.p2j.util.SessionUtils$1.initialValue(SessionUtils.java:153)
    at com.goldencode.p2j.util.SessionUtils$1.initialValue(SessionUtils.java:137)
    at com.goldencode.p2j.security.ContextLocal.get(ContextLocal.java:492)
    at com.goldencode.p2j.security.ContextLocal.get(ContextLocal.java:430)
    at com.goldencode.p2j.util.SessionUtils.getSessionTooltips(SessionUtils.java:858)
    at com.goldencode.p2j.ui.LogicalTerminal.getSessionTooltips(LogicalTerminal.java:15403)
    at com.goldencode.p2j.ui.LogicalTerminalMethodAccess.invoke(Unknown Source)
    at com.goldencode.p2j.util.MethodInvoker.invoke(MethodInvoker.java:156)
    at com.goldencode.p2j.net.Dispatcher.processInbound(Dispatcher.java:757)
    at com.goldencode.p2j.net.Conversation.block(Conversation.java:412)
    at com.goldencode.p2j.net.Conversation.run(Conversation.java:232)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: code size limit exceeded
    at sun.misc.ProxyGenerator.generateStaticInitializer(ProxyGenerator.java:1261)
    at sun.misc.ProxyGenerator.generateClassFile(ProxyGenerator.java:484)
    at sun.misc.ProxyGenerator.generateProxyClass(ProxyGenerator.java:339)
    at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:639)
    at java.lang.reflect.Proxy$ProxyClassFactory.apply(Proxy.java:557)
    at java.lang.reflect.WeakCache$Factory.get(WeakCache.java:230)
    at java.lang.reflect.WeakCache.get(WeakCache.java:127)
    at java.lang.reflect.Proxy.getProxyClass0(Proxy.java:419)
    at java.lang.reflect.Proxy.newProxyInstance(Proxy.java:719)
    at com.goldencode.p2j.util.handle.<clinit>(handle.java:335)
    ... 30 more

My question was: Are we reaching some upper limit (var1.code.size() > 65535) with the handle hierarchy?

Constantin responded by email:

I think the problem is with the HandleCommon interface - if you added a new interface there, we might reach a limit... see this, the bug looks reported but not solved: https://bugs.openjdk.java.net/browse/JDK-7189284

Try switching to our custom ProxyFactory.getProxy, and see how it behaves.

I was able to confirm this: meanwhile, I temporarily removed (commented out) one of the existing inetrfaces from extended interfaces in HandleCommon so FWD works now for me. I will try the custom proxy factory later and let you know of the outcome.

I found the following patch to work fine:

--- src/com/goldencode/p2j/util/handle.java
+++ patched/src/com/goldencode/p2j/util/handle.java
@@ -1,4 +1,3 @@
-      ClassLoader cl = MultiClassLoader.class.getClassLoader();
-      Class<?>[] ifaces = new Class<?>[] { HandleCommon.class };
-      InvalidAttributeAccess handler = new InvalidAttributeAccess();
-      invalidAttrAccessProxy = (HandleCommon) Proxy.newProxyInstance(cl, ifaces, handler);
+      invalidAttrAccessProxy = ProxyFactory.getProxy(handle.class, 
+                                                     new Class<?>[] { HandleCommon.class },
+                                                     new InvalidAttributeAccess());

I will add it to my currently assigned branch (3809c). If you encounter the NPE from description please use this until it gets into trunk.

While working with the new proxy I encountered the following exception:

Caused by: java.lang.AbstractMethodError: Method com/goldencode/p2j/util/$__Proxy0.name()Lcom/goldencode/p2j/util/character; is abstract
        at com.goldencode.p2j.util.$__Proxy0.name(Unknown Source)
        [...] 

I will investigate this issue tomorrow.

Apparently, the exception was caused because the proxy was implementing only the declaring methods. In HandleCommon there are none, all methods being declared in its super-interfaces. I changed the factory method to one more explicit and, after recompiling the project, the AbstractMethodError is gone.

Here is the new patch (without the H-entry and imports updates). Notice the InvalidAttributeAccess must be public in order to be accessed from the inside.

--- src/com/goldencode/p2j/util/handle.java
+++ patched/src/com/goldencode/p2j/util/handle.java
@@ -329,10 +331,9 @@

    static
    {
-      ClassLoader cl = MultiClassLoader.class.getClassLoader();
-      Class<?>[] ifaces = new Class<?>[] { HandleCommon.class };
-      InvalidAttributeAccess handler = new InvalidAttributeAccess();
-      invalidAttrAccessProxy = (HandleCommon) Proxy.newProxyInstance(cl, ifaces, handler);
+      invalidAttrAccessProxy = ProxyFactory.getProxy(InvalidAttributeAccess.class,
+                                                     new Class<?>[] { HandleCommon.class },
+                                                     false, null);
    }

    /**
@@ -3601,7 +3602,7 @@
    /**
     * Handler for the {@link #invalidAttrAccessProxy} proxy.
     */
-   private static class InvalidAttributeAccess
+   public static class InvalidAttributeAccess
    implements InvocationHandler
    {
       /**

Ovidiu, do you have a final fix for this?

The update from note4 looks fine in my tests.