package net.jcip.examples;

import java.io.PrintWriter;

import java.io.Writer;

import java.util.concurrent.*;

import net.jcip.annotations.*;

/**

* LogService

* <p/>

* Adding reliable cancellation to LogWriter

*

* @author Brian Goetz and Tim Peierls

*/

public class LogService {

private final BlockingQueue<String> queue;

private final LoggerThread loggerThread;

private final PrintWriter writer;

@GuardedBy("this") private boolean isShutdown;

@GuardedBy("this") private int reservations;

public LogService(Writer writer) {

this.queue = new LinkedBlockingQueue<String>();

this.loggerThread = new LoggerThread();

this.writer = new PrintWriter(writer);

}

public void start() {

loggerThread.start();

}

public void stop() {

synchronized (this) {

isShutdown = true;

}

loggerThread.interrupt();

}

public void log(String msg) throws InterruptedException {

synchronized (this) {

if (isShutdown)

throw new IllegalStateException(/*...*/);

++reservations;

}

queue.put(msg);

}

private class LoggerThread extends Thread {

public void run() {

try {

while (true) {

try {

synchronized (LogService.this) {

if (isShutdown && reservations == 0)

break;

}

String msg = queue.take();

synchronized (LogService.this) {

--reservations;

}

writer.println(msg);

} catch (InterruptedException e) { /* retry */

}

}

} finally {

writer.close();

}

}

}

}