最近项目中要用到多线程处理任务，自然就用到了ThreadPoolTaskExecutor这个对象，这个是spring对于Java的concurrent包下的ThreadPoolExecutor类的封装，对于超出等待队列大小的任务默认是使用RejectedExecutionHandler去处理拒绝的任务，而这个Handler的默认策略是AbortPolicy，直接抛出RejectedExecutionException异常，这个不符合我们的业务场景，我希望是对于超出的任务，主线程进行阻塞，直到有可用线程，简单的代码如下
ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
//默认线程池建立的线程数，当多余的线程处于空闲状态时，大于这个数字的线程会自动销毁
taskExecutor.setCorePoolSize(10);
//最大的线程数
taskExecutor.setMaxPoolSize(10);
//等待队列数，这里为了测试方便设置为0，实际可根据具体场景设置
taskExecutor.setQueueCapacity(0);
taskExecutor.setRejectedExecutionHandler(new RejectedExecutionHandler() {
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
if (!executor.isShutdown()) {
try {
log.info("start get queue");
executor.getQueue().put(r);
log.info("end get queue");
} catch (InterruptedException e) {
log.error(e.toString(), e);
Thread.currentThread().interrupt();
}
}
}
}
);
taskExecutor.initialize();
for (int i = 0; i < 100; i++) {
final int index = i;
taskExecutor.execute(new Runnable() {
@Override
public void run() {
try {
log.info("thread start " + index);
Thread.sleep(200000);
log.info("thread end " + index);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
}
结果输出：
INFO 2018-11-15 12:41:00,115 [scheduler-ssmQuartz_Worker-1] org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor: Initializing ExecutorService
INFO 2018-11-15 12:41:00,116 [ThreadPoolTaskExecutor-1] com.bocsh.base.quartz.TimingCardUpdate: thread start 0
INFO 2018-11-15 12:41:00,116 [ThreadPoolTaskExecutor-2] com.bocsh.base.quartz.TimingCardUpdate: thread start 1
INFO 2018-11-15 12:41:00,116 [ThreadPoolTaskExecutor-3] com.bocsh.base.quartz.TimingCardUpdate: thread start 2
INFO 2018-11-15 12:41:00,116 [ThreadPoolTaskExecutor-4] com.bocsh.base.quartz.TimingCardUpdate: thread start 3
INFO 2018-11-15 12:41:00,116 [ThreadPoolTaskExecutor-5] com.bocsh.base.quartz.TimingCardUpdate: thread start 4
INFO 2018-11-15 12:41:00,117 [ThreadPoolTaskExecutor-6] com.bocsh.base.quartz.TimingCardUpdate: thread start 5
INFO 2018-11-15 12:41:00,117 [ThreadPoolTaskExecutor-7] com.bocsh.base.quartz.TimingCardUpdate: thread start 6
INFO 2018-11-15 12:41:00,117 [ThreadPoolTaskExecutor-9] com.bocsh.base.quartz.TimingCardUpdate: thread start 8
INFO 2018-11-15 12:41:00,117 [scheduler-ssmQuartz_Worker-1] com.bocsh.base.quartz.TimingCardUpdate: start get queue
INFO 2018-11-15 12:41:00,117 [ThreadPoolTaskExecutor-8] com.bocsh.base.quartz.TimingCardUpdate: thread start 7
INFO 2018-11-15 12:41:00,117 [ThreadPoolTaskExecutor-10] com.bocsh.base.quartz.TimingCardUpdate: thread start 9
INFO 2018-11-15 12:44:20,116 [ThreadPoolTaskExecutor-4] com.bocsh.base.quartz.TimingCardUpdate: thread end 3
INFO 2018-11-15 12:44:20,116 [ThreadPoolTaskExecutor-2] com.bocsh.base.quartz.TimingCardUpdate: thread end 1
INFO 2018-11-15 12:44:20,116 [ThreadPoolTaskExecutor-4] com.bocsh.base.quartz.TimingCardUpdate: thread start 10
INFO 2018-11-15 12:44:20,116 [ThreadPoolTaskExecutor-3] com.bocsh.base.quartz.TimingCardUpdate: thread end 2
INFO 2018-11-15 12:44:20,116 [ThreadPoolTaskExecutor-1] com.bocsh.base.quartz.TimingCardUpdate: thread end 0
INFO 2018-11-15 12:44:20,116 [scheduler-ssmQuartz_Worker-1] com.bocsh.base.quartz.TimingCardUpdate: end get queue
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-1] com.bocsh.base.quartz.TimingCardUpdate: thread start 11
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-6] com.bocsh.base.quartz.TimingCardUpdate: thread end 5
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-5] com.bocsh.base.quartz.TimingCardUpdate: thread end 4
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-7] com.bocsh.base.quartz.TimingCardUpdate: thread end 6
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-9] com.bocsh.base.quartz.TimingCardUpdate: thread end 8
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-10] com.bocsh.base.quartz.TimingCardUpdate: thread end 9
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-8] com.bocsh.base.quartz.TimingCardUpdate: thread end 7
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-3] com.bocsh.base.quartz.TimingCardUpdate: thread start 12
INFO 2018-11-15 12:44:20,117 [ThreadPoolTaskExecutor-2] com.bocsh.base.quartz.TimingCardUpdate: thread start 13
INFO 2018-11-15 12:44:20,117 [scheduler-ssmQuartz_Worker-1] com.bocsh.base.quartz.TimingCardUpdate: start get queue
INFO 2018-11-15 12:44:20,120 [scheduler-ssmQuartz_Worker-1] com.bocsh.base.quartz.TimingCardUpdate: end get queue
INFO 2018-11-15 12:44:20,120 [ThreadPoolTaskExecutor-8] com.bocsh.base.quartz.TimingCardUpdate: thread start 14
INFO 2018-11-15 12:44:20,120 [ThreadPoolTaskExecutor-10] com.bocsh.base.quartz.TimingCardUpdate: thread start 15
INFO 2018-11-15 12:44:20,120 [ThreadPoolTaskExecutor-5] com.bocsh.base.quartz.TimingCardUpdate: thread start 18
INFO 2018-11-15 12:44:20,120 [ThreadPoolTaskExecutor-7] com.bocsh.base.quartz.TimingCardUpdate: thread start 17
INFO 2018-11-15 12:44:20,120 [ThreadPoolTaskExecutor-9] com.bocsh.base.quartz.TimingCardUpdate: thread start 16
INFO 2018-11-15 12:44:20,120 [scheduler-ssmQuartz_Worker-1] com.bocsh.base.quartz.TimingCardUpdate: start get queue
INFO 2018-11-15 12:44:20,120 [ThreadPoolTaskExecutor-6] com.bocsh.base.quartz.TimingCardUpdate: thread start 19
可以看到，在任务超过线程池大小后，start get queue后会阻塞。
这里之所以能实现阻塞，是基于BlockingQueue的put方法来实现的，当阻塞队列满时，put方法会一直等待
参考文章： 让Java线程池实现任务阻塞执行的一种可行方案
