[jboss-cvs] JBoss Messaging SVN: r1774 - trunk/src/main/org/jboss/jms/util

[jboss-cvs-commits at lists.jboss.org]

Author: clebert.suconic at jboss.com
Date: 2006-12-12 20:02:57 -0500 (Tue, 12 Dec 2006)
New Revision: 1774

Added:
   trunk/src/main/org/jboss/jms/util/Valve.java
Log:
implementing client valve

Added: trunk/src/main/org/jboss/jms/util/Valve.java
===================================================================
--- trunk/src/main/org/jboss/jms/util/Valve.java	2006-12-12 20:04:43 UTC (rev 1773)
+++ trunk/src/main/org/jboss/jms/util/Valve.java	2006-12-13 01:02:57 UTC (rev 1774)
@@ -0,0 +1,100 @@
+/*
+   * JBoss, Home of Professional Open Source
+   * Copyright 2005, JBoss Inc., and individual contributors as indicated
+   * by the @authors tag. See the copyright.txt in the distribution for a
+   * full listing of individual contributors.
+   *
+   * This is free software; you can redistribute it and/or modify it
+   * under the terms of the GNU Lesser General Public License as
+   * published by the Free Software Foundation; either version 2.1 of
+   * the License, or (at your option) any later version.
+   *
+   * This software is distributed in the hope that it will be useful,
+   * but WITHOUT ANY WARRANTY; without even the implied warranty of
+   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+   * Lesser General Public License for more details.
+   *
+   * You should have received a copy of the GNU Lesser General Public
+   * License along with this software; if not, write to the Free
+   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
+   */
+
+package org.jboss.jms.util;
+
+
+/**
+ * This class is used to guarantee only one thread will be performing a given function, and if any other
+ * thread tries to execute the same functionality it will just ignored
+ * <pre>
+     Valve valve = new Valve();
+        if (valve.open())
+        {
+             try
+             {
+                doSomething();
+             }
+             finally
+             {
+                valve.close();
+             }
+        }
+        else
+        {
+             System.out.println("Nothing to be done
+        }
+  </pre>
+
+   <p>Notice that you can call close only once, so only call close if you were able to open the valve.</p>
+   <p>After its usage if you decide to reset you should just create a new Valve in a safe synchronized block, so
+        if any other thread still using the variable you do it in a safe way </p>
+
+ * @see org.jboss.test.messaging.jms.VeryBasicValveTest
+ * @author <a href="mailto:clebert.suconic at jboss.com">Clebert Suconic</a>
+ *  */
+public class Valve
+{
+   boolean opened;
+   boolean closed;
+
+
+   public boolean open() throws Exception
+   {
+      return open(true);
+   }
+
+   public synchronized boolean open(boolean wait) throws Exception
+   {
+      // already opened? then needs to wait to be closed
+      if (opened)
+      {
+         // if not closed yet, will wait to be closed
+         if (!closed)
+         {
+            if (wait)
+            {
+               this.wait();
+            }
+         }
+         return false;
+      } else
+      {
+         opened = true;
+         return true;
+      }
+   }
+
+   public synchronized void close()
+   {
+      if (!opened)
+      {
+         throw new IllegalStateException("Open must be called first");
+      }
+      if (closed)
+      {
+         throw new IllegalStateException("Valve is already closed");
+      }
+      closed = true;
+      notifyAll();
+   }
+}