为Java应用程序加上退出事件处理(ShutdownHook)
ShutdownHook 是这样一个概念:向虚拟机注册一个线程,当程序退出(Ctrl+C)时虚拟机会启动这个线程,我们可以在这个线程的run()中做一些清除的工作,如:释放数据库连接,关闭文件等.
注册:
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注销:
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请注意, 该 hook 线程必须是已经初始化但是没有运行的线程, 这个线程将在虚拟机响应用户的中断之前运行, 例如按下 ^C, 或者系统范围的事件, 例如注销或者关闭系统时.
[例子]
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运行结果:
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可以看到:当程序退出时启动了TestThread线程,执行了定义的释放工作。