如果是web項(xiàng)目，會(huì)啟動(dòng)端口監(jiān)聽，主線程阻塞不會(huì)退出。但如果是普通的java項(xiàng)目對(duì)外提供服務(wù)，主線程一旦跑完，整個(gè)進(jìn)程就退出了。
之前見過有使用死循環(huán)方式來防止退出的。著實(shí)捏了把冷汗，這會(huì)導(dǎo)致cpu占用變高。那有沒有更優(yōu)雅的方式呢，我從阿里開源RPC框架dubbo中找到了答案

public class StartMain {
    
    private static final ReentrantLock LOCK = new ReentrantLock();
    private static final Condition STOP = LOCK.newCondition();
  
    public static void main(String[] args) {


        AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        applicationContext.start();
        logger.info("service start success !~");
        addHook(applicationContext);
        //主線程阻塞等待，守護(hù)線程釋放鎖后退出
        try {
            LOCK.lock();
            STOP.await();
        } catch (InterruptedException e) {
            logger.warn(" service   stopped, interrupted by other thread!", e);
        } finally {
            LOCK.unlock();
        }

    }

    /**
     * Created on 2017年12月12日
     * <p>
     * Discription:[添加一個(gè)守護(hù)線程]
     *
     * @param applicationContext
     * 
     */
    private static void addHook(AbstractApplicationContext applicationContext) {
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {

            try {
               
                applicationContext.stop();
            } catch (Exception e) {
                logger.error("StartMain stop exception ", e);
            }

            logger.info("jvm exit, all service stopped.");
            try {
                LOCK.lock();
                STOP.signal();
            } finally {
                LOCK.unlock();
            }
        }, "StartMain-shutdown-hook"));
    }

}