6.2 线程池的扩展beforeExecute和afterExecute参数说明和使用示例

线程池ThreadPoolExecutor为了提供扩展，提供了protected的两个方法beforeExecute和 afterExecute，每个任务执行前后都会调用这两个方法，相当于对线程任务的执行做了一个切面

线程池中定义的两个空方法

public class ThreadPoolExecutor extends AbstractExecutorService {
    /**     
     * @param t 执行任务的线程
     * @param r 将要被执行的任务
     */
    protected void beforeExecute(Thread t, Runnable r) { }

    /**
     * @param r 将要被执行的任务
     * @param t 异常信息
     */
    protected void afterExecute(Runnable r, Throwable t) { }
}

测试示例

public class MyThreadPoolExpand {
    static class Customer extends Thread{
        private String name;
        private Random random = new Random();
        public Customer(String name){
            this.name = name;
        }
        @Override
        public void run() {
            System.out.println(this.name+":加入线程池");
            try {
                Thread.sleep(random.nextInt(100)*6);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(2,4,5,
                TimeUnit.SECONDS,new ArrayBlockingQueue<>(9),new ThreadPoolExecutor.DiscardOldestPolicy()){
            /**
             *
             * @param t   执行任务的线程
             * @param r 将要被执行的任务
             */
            @Override
            protected void beforeExecute(Thread t, Runnable r) {
                System.out.println(((Customer)r).name + "：beforeExecute将要被执行");
            }

            @Override
            protected void afterExecute(Runnable r, Throwable t) {
                System.out.println(((Customer)r).name + "：afterExecute已经执行完毕");

            }
        };
        for (int i = 0; i < 10; i++) {
            poolExecutor.execute(new Customer("customer-"+i));
        }
        poolExecutor.shutdown();
    }
}

结果：

D:\install\jdk8\bin\java.exe "-javaagent:D:\install\intellij2019\IntelliJ IDEA 2019.1.3\lib\idea_rt.jar=6496:D:\install\intellij2019\IntelliJ IDEA 2019.1.3\bin" -Dfile.encoding=UTF-8 -classpath D:\install\jdk8\jre\lib\charsets.jar;D:\install\jdk8\jre\lib\deploy.jar;D:\install\jdk8\jre\lib\ext\access-bridge-64.jar;D:\install\jdk8\jre\lib\ext\cldrdata.jar;D:\install\jdk8\jre\lib\ext\dnsns.jar;D:\install\jdk8\jre\lib\ext\jaccess.jar;D:\install\jdk8\jre\lib\ext\jfxrt.jar;D:\install\jdk8\jre\lib\ext\localedata.jar;D:\install\jdk8\jre\lib\ext\nashorn.jar;D:\install\jdk8\jre\lib\ext\sunec.jar;D:\install\jdk8\jre\lib\ext\sunjce_provider.jar;D:\install\jdk8\jre\lib\ext\sunmscapi.jar;D:\install\jdk8\jre\lib\ext\sunpkcs11.jar;D:\install\jdk8\jre\lib\ext\zipfs.jar;D:\install\jdk8\jre\lib\javaws.jar;D:\install\jdk8\jre\lib\jce.jar;D:\install\jdk8\jre\lib\jfr.jar;D:\install\jdk8\jre\lib\jfxswt.jar;D:\install\jdk8\jre\lib\jsse.jar;D:\install\jdk8\jre\lib\management-agent.jar;D:\install\jdk8\jre\lib\plugin.jar;D:\install\jdk8\jre\lib\resources.jar;D:\install\jdk8\jre\lib\rt.jar;F:\享学\2、第二期课程\（01）并发编程——mark老师\10-2019.05.12-并发编程第十节课\vip-v2-concurrent\concurrent\target\classes;D:\install\maven\maven-repository\commons-lang\commons-lang\2.6\commons-lang-2.6.jar;D:\install\maven\maven-repository\io\netty\netty-all\4.1.28.Final\netty-all-4.1.28.Final.jar cn.enjoyedu.ch6.MyThreadPoolExpand
customer-1：beforeExecute将要被执行
customer-0：beforeExecute将要被执行
customer-0:加入线程池
customer-1:加入线程池
customer-0：afterExecute已经执行完毕
customer-2：beforeExecute将要被执行
customer-2:加入线程池
customer-2：afterExecute已经执行完毕
customer-3：beforeExecute将要被执行
customer-3:加入线程池
customer-1：afterExecute已经执行完毕
customer-4：beforeExecute将要被执行
customer-4:加入线程池
customer-3：afterExecute已经执行完毕
customer-5：beforeExecute将要被执行
customer-5:加入线程池
customer-4：afterExecute已经执行完毕
customer-6：beforeExecute将要被执行
customer-6:加入线程池
customer-6：afterExecute已经执行完毕
customer-7：beforeExecute将要被执行
customer-7:加入线程池
customer-7：afterExecute已经执行完毕
customer-8：beforeExecute将要被执行
customer-8:加入线程池
customer-8：afterExecute已经执行完毕
customer-9：beforeExecute将要被执行
customer-9:加入线程池
customer-5：afterExecute已经执行完毕
customer-9：afterExecute已经执行完毕

Process finished with exit code 0