Initial Comment that contains a mostly completed version of this

little tool.

pom.xml

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+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.valhalla.tools.net</groupId>
+  <artifactId>net-proc-comm-tool</artifactId>
+  <version>1.0.0</version>
+  <packaging>jar</packaging>
+
+  <name>net-ipc-tools</name>
+  <url>http://maven.apache.org</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+  </properties>
+
+  <dependencies>
+  	<dependency>
+  		<groupId>junit</groupId>
+  		<artifactId>junit</artifactId>
+  		<version>4.8.2</version>
+  		<scope>test</scope>
+  		<optional>false</optional>
+  	</dependency>
+  	<dependency>
+  		<groupId>org.slf4j</groupId>
+  		<artifactId>slf4j-api</artifactId>
+  		<version>1.6.4</version>
+  	</dependency>
+  	<dependency>
+  		<groupId>org.valhalla.tools.process</groupId>
+  		<artifactId>process-ipc-tools</artifactId>
+  		<version>1.0.2</version>
+  		<scope>test</scope>
+  	</dependency>
+  	<dependency>
+  		<groupId>ch.qos.logback</groupId>
+  		<artifactId>logback-core</artifactId>
+  		<version>1.0.0</version>
+  		<scope>test</scope>
+  	</dependency>
+  	<dependency>
+  		<groupId>ch.qos.logback</groupId>
+  		<artifactId>logback-classic</artifactId>
+  		<version>1.0.0</version>
+  		<scope>test</scope>
+  	</dependency>
+  </dependencies>
+</project>

src/main/java/org/valhalla/tools/net/CommandExecutor.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.valhalla.tools.net;
+
+import java.io.Serializable;
+
+/**
+ * This is the main interface that all users of this library will be required to
+ * implement.  This interface implementation will have intimate knowledge of what
+ * actions need to be performed on the passed instances.  The current library 
+ * has no claims on this and leaves it to the user of this library.
+ * 
+ * @author Claudio Corsi
+ *
+ */
+public interface CommandExecutor<S, R> extends Serializable {
+
+	/**
+	 * This method will apply the given changes to the passed instance.
+	 * It will return a reply to be sent to the remote process.  The
+	 * returned instance can be null.
+	 * 
+	 * @param destination The instance that this instance will perform
+	 *        the given request/reply
+	 *        
+	 * @return An instance of a CommandExecutor that will be sent to
+	 *         the requesting/replying process.  This can be null
+	 */
+	CommandExecutor<R, S> apply(S destination);
+
+}

src/main/java/org/valhalla/tools/net/ServiceClient.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.valhalla.tools.net;
+
+import java.net.Socket;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This ServiceClient class is used to communicate with the ServiceServer instance and
+ * implements all of the required calls to be able to receive and send CommandExecutor
+ * instances between this process and the server process.
+ *   
+ * @author Claudio Corsi
+ *
+ */
+public class ServiceClient<C, S> {
+
+	private static final Logger logger = LoggerFactory.getLogger(ServiceClient.class);
+
+	private CountDownLatch       shutdown = new CountDownLatch(1);
+	private ServiceManager<C, S> manager  = null;
+	private String               hostname;
+	private AtomicBoolean        started;
+
+	/**
+	 * This default constructor will assume that the service server instance is located
+	 * on the same host as this process.  This is similar to passing "localhost" to the
+	 * constructor that expects a hostname.
+	 */
+	public ServiceClient() {
+		this("localhost");
+	}
+
+	/**
+	 * This method will create an instance of the service client that will be used to 
+	 * communicate to the service server instance that is located within the passed
+	 * host name.
+	 * 
+	 * @param hostname the name of the host that the service server instance is located
+	 * 
+	 */
+	public ServiceClient(String hostname) {
+		this.hostname = hostname;
+	}
+
+	/**
+	 * This method is used to start the process of communicating with the service
+	 * server instance for the passed host name.  This method will setup the 
+	 * socket communication and instantiate the ServiceManager instance that is
+	 * used to communicate with the service manager instance of the service 
+	 * server. </br>
+	 * 
+	 * This method can only be called once per instance.  Any subsequent calls to
+	 * this method will generate and IllegalArgumentException. 
+	 * 
+	 * @param client the client instance that received CommandExecutor instances
+	 *   are applied to.
+	 *   
+	 * @throws Exception If any exceptions are raised when trying to setup the 
+	 *   socket communication between this service client and the service server.
+	 *   
+	 */
+	public void execute(final C client) throws Exception {
+		if (started.compareAndSet(false, true) == false) {
+			logger.error("The execute method was called multiple times which is not allowed.");
+			throw new IllegalStateException("This method can only be called once");
+		}
+
+		// TODO: Should we be creating a thread that will then perform a callback
+		//       action to inform the calling process that the ServiceManager was
+		//       successfully created and is ready to perform CommandExecutor
+		//       processing.
+		//       It might not be necessary since the ServiceManager instance already
+		//       spawns a thread to process the CommandExecutor actions.
+
+		// This is the main point of entry that we will be using to 
+		// test the new feature...
+		int port = Integer.getInteger(ServiceConstants.SERVICE_MANAGER_PORT_NAME, 0);
+		if (port <= 0) {
+			logger.info("No service manager port number was defined");
+			throw new IllegalArgumentException("The service manager port is invalid: " + port);
+		}
+		Socket socket = new Socket(hostname, port);
+		try {
+			logger.info("Creating Service Manager instance");
+			manager =  new ServiceManager<C, S>(socket, client);
+			// Now that we started the manager we just wait until we are told to 
+			// finish....
+			logger.info("Waiting to be told that I am done");
+			shutdown.await();
+		} finally {
+			logger.info("Exiting client application");
+			if (manager != null) {
+				// Closing the manager causes the socket to be closed also...
+				manager.stop();
+			} else {
+				// Close the opened socket...
+				socket.close();
+			}
+		}
+	}
+
+	/**
+	 * This method is called whenever you want to shutdown the communication between
+	 * this client service manager and the server service manager.
+	 * 
+	 */
+	public void shutdown() {
+		this.shutdown.countDown();
+	}
+
+	/**
+	 * This method will return this instance service manager instance.
+	 * 
+	 * @return the service manager instance
+	 */
+	public ServiceManager<C, S> getManager() {
+		return manager;
+	}
+
+}

src/main/java/org/valhalla/tools/net/ServiceConstants.java

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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.valhalla.tools.net;
+
+/**
+ * @author Claudio Corsi
+ *
+ */
+public interface ServiceConstants {
+
+	String SERVICE_MANAGER_PORT_NAME = "service.manager.port";
+
+}