Some basic GWT infrastructure.

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@6177 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/web/Base.gwt.xml

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+<module>
+  <source path="gwt"/>
+</module>

src/java/com/threerings/web/gwt/ServiceException.java

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+//
+// $Id: ServiceException.java 12616 2008-10-17 21:40:55Z mdb $
+
+package com.threerings.web.gwt;
+
+import com.google.gwt.user.client.rpc.IsSerializable;
+
+/**
+ * An exception thrown by a remote service when it wishes to communicate a
+ * particular error message to a user.
+ */
+public class ServiceException extends Exception
+    implements IsSerializable
+{
+    /**
+     * Creates a service exception with the supplied translation message.
+     */
+    public ServiceException (String message)
+    {
+        _message = message;
+    }
+
+    /**
+     * Default constructor for use when unserializing.
+     */
+    public ServiceException ()
+    {
+    }
+
+    @Override // from Exception
+    public String getMessage ()
+    {
+        // we have to return our own message because GWT won't serialize anything in our parent
+        // class without a bunch of annoying fiddling
+        return _message;
+    }
+
+    protected String _message;
+}

src/java/com/threerings/web/server/ServletWaiter.java

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+//
+// $Id: ServletWaiter.java 13028 2008-10-31 21:52:05Z jamie $
+
+package com.threerings.web.server;
+
+import java.util.concurrent.Callable;
+
+import com.samskivert.servlet.util.ServiceWaiter;
+import com.samskivert.util.RunQueue;
+
+import com.threerings.presents.data.InvocationCodes;
+import com.threerings.presents.server.InvocationException;
+import com.threerings.web.gwt.ServiceException;
+
+import static com.threerings.admin.Log.log;
+
+/**
+ * Used to bridge the gap between synchronous servlets and our asynchronous
+ * game server architecture.
+ *
+ * <p> We don't want to use service waiters as a permanent solution, as that
+ * will result in a zillion servlet threads hanging around waiting for results
+ * all over the goddamned place. Instead we want to rearchitect Jetty to
+ * support asynchronous servlets that give up their thread when they need to
+ * block and grab a new thread out of the pool when they're ready to go
+ * again. This is a tall order, but I think they might be working on something
+ * like this for Jetty 6.0.
+ */
+public class ServletWaiter<T> extends ServiceWaiter<T>
+{
+    public ServletWaiter (String ident)
+    {
+        _ident = ident;
+    }
+
+    /**
+     * Waits for our asynchronous result and returns it if all is well. If
+     * anything goes wrong (a timeout or a asynchronous call failure) the
+     * exception is logged and a {@link ServiceException} is thrown.
+     */
+    public T waitForResult ()
+        throws ServiceException
+    {
+        try {
+            if (waitForResponse()) {
+                return getArgument();
+            } else {
+                throw getError();
+            }
+
+        } catch (InvocationException ie) {
+            // pass these through without a fuss
+            throw new ServiceException(ie.getMessage());
+
+        } catch (Exception e) {
+            log.warning(_ident + " failed.", e);
+            throw new ServiceException(InvocationCodes.E_INTERNAL_ERROR);
+        }
+    }
+
+    /**
+     * Posts a result getter to be executed on the run queue thread and blocks waiting for the
+     * result.
+     */
+    public static <T> T queueAndWait (
+        RunQueue runq, final String name, final Callable<T> action)
+        throws ServiceException
+    {
+        final ServletWaiter<T> waiter = new ServletWaiter<T>(name);
+        runq.postRunnable(new Runnable() {
+            public void run () {
+                try {
+                    waiter.postSuccess(action.call());
+                } catch (final Exception e) {
+                    waiter.postFailure(e);
+                }
+            }
+        });
+        return waiter.waitForResult();
+    }
+
+    protected String _ident;
+}