有时候我们用到的程序不一定总是在JVM里面驻守,可能调用完就不用了,释放资源.
RunTime.getRunTime().addShutdownHook的作用就是在JVM销毁前执行的一个线程.
当然这个线程依然要自己写.
利用这个性质,如果我们之前定义了一系列的线程池供程序本身使用,那么就可以在这个最后执行的线程中把这些线程池优雅的关闭掉.
比如我们定义了一个线程池
private ExecutorService streamThreadPool = Executors.newFixedThreadPool(streamNum);
然后我们需要对它进行优雅关闭
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
shutdownGracefully();
}
});
public void shutdownGracefully() {
shutdownThreadPool(streamThreadPool, "main-pool");
}
/**
* 优雅关闭线程池
* @param threadPool
* @param alias
*/
private void shutdownThreadPool(ExecutorService threadPool, String alias) {
log.info("Start to shutdown the thead pool: {}", alias);
threadPool.shutdown(); // 使新任务无法提交.
try {
// 等待未完成任务结束
if (!threadPool.awaitTermination(60, TimeUnit.SECONDS)) {
threadPool.shutdownNow(); // 取消当前执行的任务
log.warn("Interrupt the worker, which may cause some task inconsistent. Please check the biz logs.");
// 等待任务取消的响应
if (!threadPool.awaitTermination(60, TimeUnit.SECONDS))
log.error("Thread pool can't be shutdown even with interrupting worker threads, which may cause some task inconsistent. Please check the biz logs.");
}
} catch (InterruptedException ie) {
// 重新取消当前线程进行中断
threadPool.shutdownNow();
log.error("The current server thread is interrupted when it is trying to stop the worker threads. This may leave an inconcistent state. Please check the biz logs.");
// 保留中断状态
Thread.currentThread().interrupt();
}
log.info("Finally shutdown the thead pool: {}", alias);
}
这样我们就可以在JVM销毁前无论有没有执行的线程都会进行中断,然后关闭线程池.