A ServiceWaiter that doesn't know about those stinking InvocationServices.

git-svn-id: https://samskivert.googlecode.com/svn/trunk@1193 6335cc39-0255-0410-8fd6-9bcaacd3b74c
2003-08-12 23:44:33 +00:00
parent 5f41b5ea96
commit 70ad6989fd
1 changed files with 151 additions and 0 deletions
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+//
+// $Id: ServiceWaiter.java,v 1.1 2003/08/12 23:44:33 ray Exp $
+
+package com.samskivert.servlet.util;
+
+import com.samskivert.Log;
+import com.samskivert.servlet.RedirectException;
+import com.samskivert.util.ResultListener;
+
+/**
+ * A handy base class for issuing server-side service requests and
+ * awaiting their responses from within a servlet.
+ *
+ * <em>Note:</em> You might think that it would be keen to use this
+ * anonymously like so:
+ *
+ * <pre>
+ * ServiceWaiter waiter = new ServiceWaiter() {
+ *     public void handleSuccess (int invid, ...) {
+ *         // handle success
+ *     }
+ *     // ...
+ * };
+ * </pre>
+ *
+ * But that won't work because public methods in anonymous inner classes
+ * do not have public visibility and so the invocation manager will not be
+ * able to reflect your response methods when the time comes to deliver
+ * the response. Unfortunately, there appears to be no manner in which to
+ * instruct the Java compiler to give public scope to an anonymous inner
+ * class rather than default scope. Sigh.
+ */
+public class ServiceWaiter
+    implements ResultListener
+{
+    /**
+     * Construct a ServiceWaiter with the default (30 second) timeout.
+     */
+    public ServiceWaiter ()
+    {
+        this(DEFAULT_WAITER_TIMEOUT);
+    }
+
+    /**
+     * Construct a ServiceWaiter with the specified timeout.
+     *
+     * @param timeout the timeout, in seconds.
+     */
+    public ServiceWaiter (int timeout)
+    {
+        _timeout = timeout;
+    }
+
+    /**
+     * Marks the request as successful and posts the supplied response
+     * argument for perusal by the caller.
+     */
+    public synchronized void postSuccess (Object arg)
+    {
+        _success = 1;
+        _argument = arg;
+        notify();
+    }
+
+    /**
+     * Marks the request as failed and posts the supplied response
+     * argument for perusal by the caller.
+     */
+    public synchronized void postFailure (Object arg)
+    {
+        _success = -1;
+        _argument = arg;
+        notify();
+    }
+
+    /**
+     * Returns the argument posted by the waiter when the response
+     * arrived.
+     */
+    public Object getArgument ()
+    {
+        return _argument;
+    }
+
+    /**
+     * Blocks waiting for the response.
+     *
+     * @return true if a success response was posted, false if a failure
+     * repsonse was posted.
+     */
+    public synchronized boolean awaitResponse ()
+        throws RedirectException
+    {
+        while (_success == 0) {
+            try {
+                // wait for the response, timing out after a while
+                wait(1000L * _timeout);
+
+                // if we get here without some sort of response, then
+                // we've timed out and we should freak out
+                if (_success == 0) {
+                    Log.warning("Service waiter timed out.");
+                    Thread.dumpStack();
+                    throw new RedirectException(getTimeoutRedirectURL());
+                }
+
+            } catch (InterruptedException ie) {
+                // fall through and wait again
+            }
+        }
+
+        return (_success > 0);
+    }
+
+    /**
+     * Get the page to which we redirect on timeout.
+     */
+    protected String getTimeoutRedirectURL ()
+    {
+        // TODO
+        return "/";
+    }
+
+    // documentation inherited from interface ResultListener
+    public void requestCompleted (Object result)
+    {
+        postSuccess(result);
+    }
+
+    // documentation inherited from interface ResultListener
+    public void requestFailed (Exception cause)
+    {
+        postFailure((cause != null) ? cause.getMessage() : null);
+    }
+
+    /** Whether or not the response succeeded; positive for success,
+     * negative for failure, zero means we haven't received the response
+     * yet. */
+    protected int _success = 0;
+
+    /** The argument posted by the waiter upon receipt of the response. */
+    protected Object _argument;
+
+    /** How many seconds to wait before giving up the ghost. */
+    protected int _timeout;
+
+    /** If a response is not received within the specified timeout, an
+     * exception is thrown which redirects the user to an internal error
+     * page. */
+    protected static final int DEFAULT_WAITER_TIMEOUT = 30;
+}