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/* |
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* This file is part of SingleInstance. |
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* |
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* SingleInstance is free software: you can redistribute it and/or modify |
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* it under the terms of the GNU Lesser General Public License as published by |
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* the Free Software Foundation, either version 3 of the License, or |
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* (at your option) any later version. |
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* |
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* SingleInstance is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public License |
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* along with SingleInstance. If not, see <https://www.gnu.org/licenses/>. |
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* |
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* Copyright (c) 2020 Vincent Quatrevieux |
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*/ |
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package fr.quatrevieux.singleinstance; |
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import fr.quatrevieux.singleinstance.ipc.InstanceServer; |
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import java.io.IOException; |
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import java.lang.management.ManagementFactory; |
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import java.util.Optional; |
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/** |
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* Handle single instance system |
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* |
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* Usage : |
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* <pre>{@code |
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* public static void main(String[] args) { |
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* // Check single instance |
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* InstanceManager manager = new InstanceManager(); |
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* |
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* manager.find().ifPresent(distant -> { |
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* // A running instance is present : send a message and close the application |
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* distant.send("My message", args[0].getBytes()); |
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* System.exit(0); |
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* }); |
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* |
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* // Initialize application |
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* MyApp app = xxx; |
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* |
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* // Start the IPC server |
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* manager.server().ifPresent(server -> { |
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* server.consume(message -> app.handleMessage(message)); |
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* }); |
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* } |
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* }</pre> |
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*/ |
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final public class InstanceManager { |
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final private LockFile lockFile; |
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public InstanceManager() { |
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this(new LockFile()); |
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} |
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public InstanceManager(LockFile lockFile) { |
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this.lockFile = lockFile; |
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} |
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/** |
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* Try to acquire the single instance (i.e. the lock file) |
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* If the lock is acquired, the PID will be written on |
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* |
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* @return true if the current process as acquire the lock |
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* |
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* @throws IOException When cannot access to lock file |
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*/ |
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public boolean acquire() throws IOException { |
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if (lockFile.acquire()) { |
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lockFile.write(output -> output.writeInt(getCurrentPid())); |
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return true; |
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} |
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return false; |
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} |
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/** |
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* Try to get the distant instance (the first run process) |
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* |
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* Usage: |
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* <pre>{@code |
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* InstanceManager im = new InstanceManager(); |
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* im.find().ifPresent(distant -> { |
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* System.out.println("Process already running"); |
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* // Send a message to the first process |
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* distant.send("Open", args[0].getBytes()); |
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* System.exit(0); |
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* }); |
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* }</pre> |
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* |
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* @return An empty optional if the current process is the first running, or the distant instance if exists |
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* |
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* @throws IOException When cannot access to lock file |
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*/ |
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public Optional<DistantInstance> find() throws IOException { |
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return acquire() ? Optional.empty() : Optional.of(new DistantInstance(lockFile)); |
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} |
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/** |
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* Try to open the IPC server |
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* If the server is successfully opened, the port number will be written on the lock file |
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* |
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* Usage: |
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* <pre>{@code |
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* InstanceManager im = new InstanceManager(); |
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* im.server().ifPresent(server -> { |
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* server.consume(message -> { |
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* // Process received messages |
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* if (message.name().equals(xxx)) { |
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* // ... |
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* } |
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* }); |
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* }); |
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* }</pre> |
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* |
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* @return An empty optional if the current process is not the first running instance |
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* |
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* @throws IOException When cannot open the server |
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*/ |
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public Optional<InstanceServer> server() throws IOException { |
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if (!acquire()) { |
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return Optional.empty(); |
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} |
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InstanceServer server = new InstanceServer(); |
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server.open(); |
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lockFile.write(output -> { |
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output.writeInt(getCurrentPid()); |
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output.writeInt(server.port()); |
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}); |
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return Optional.of(server); |
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} |
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/** |
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* Release the lock file |
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*/ |
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public void release() { |
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lockFile.release(); |
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} |
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private int getCurrentPid() { |
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return Integer.parseInt(ManagementFactory.getRuntimeMXBean().getName().split("@", 2)[0]); |
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} |
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} |
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vincent4vx /
SingleInstance
