- cancel方法只是向子线程发起中断请求,是否能够中断取决于子线程自身,不能确定子线程会在哪一步操作退出,加入启用的有事务,这个事务可能回滚了,也可能提交成功了。因此,我们需要借用synchronized功能,让父子线程通讯,来明确获得子线程的运行状态;
- 子线程中执行数据库操作,引起死锁等待,这种情况下cancle操作是不能取消任务了,只能等到事务超时。这个问题由于cancel无法强制关闭线程,因此无法用FutureTask方案。
以下实现依然围绕FutureTask这个方案来将,只是添加父子线程通讯,明确获取子线程状态的实现。
三、代码实现:
3.1、创建一个FTaskEndFlag的线程同步标志。父线程等待子线程反馈执行结果后,再执行后续的逻辑;
package simm.framework.threadutils.interrupt;import java.util.concurrent.TimeoutException; /*** futuretask运行终止事件通知* 2018.09.22 by simm*/ public class FTaskEndFlag {private volatile boolean isNormaled = false;private volatile boolean fired = false;private Exception exception =null;public boolean isNormaled() {return isNormaled;}/*** 获取子线程异常信息* @return*/public Exception getException() {return exception;}/*** 通知结束* @param result* @param result*/public synchronized void notifyEnd(boolean result){isNormaled = result;fired = true;notifyAll();}/*** 通知结束* @param result* @param result*/public synchronized void notifyEnd(boolean result,Exception ex){isNormaled = result;exception = ex;fired = true;notifyAll();}/*** 执行结束通知*/public synchronized void waitForEnd() throws InterruptedException {while (!fired) {//子线程挂起,释放synchronized同步块 wait();}}/*** 等待*/private void waitFunc(long millis){try {Thread.sleep(millis);} catch (InterruptedException e) {e.printStackTrace();}} }
3.2、创建一个BaseFutureTask的抽象类,内置FTaskEndFlag线程同步标志;
package simm.framework.threadutils.interrupt;import java.util.concurrent.Callable;/*** 基础任务* 2018.09.22 by simm*/ public abstract class BaseFutureTask implements Callable<Boolean> {/*** futuretask 等待标志*/private FTaskEndFlag flag = new FTaskEndFlag();public FTaskEndFlag getFlag() {return flag;} }
3.3、创建一个超时重试的工具类,对FutureTask的结果获取设置超时时间;
package simm.framework.threadutils.interrupt;import java.lang.reflect.Constructor; import java.util.List; import java.util.concurrent.*; /*** 方法超时重试工具* 2018.09.20 by simm*/ public class RetryUtil {/*** 可缓存线程执行器(依jvm情况自行回收创建)*/private static ExecutorService executorService = Executors.newCachedThreadPool();/*** 默认方法(3秒超时,重试3次)* @param callable* @return* @throws InterruptedException* @throws ExecutionException* @throws TimeoutException*/public static Boolean execute(BaseFutureTask callable) throws InterruptedException, ExecutionException, TimeoutException {return execute(callable,3000,1000,3);}/*** 方法超时控制* @param callable 方法体* @param timeout 超时时长* @param interval 间隔时长* @param retryTimes 重试次数* @return* @throws ExecutionException* @throws InterruptedException* @throws TimeoutException*/public static Boolean execute(BaseFutureTask callable, long timeout,long interval, int retryTimes) throws ExecutionException, InterruptedException, TimeoutException {Boolean result = false;FutureTask<Boolean> futureTask = new FutureTask<>(callable);executorService.execute(futureTask);try {result = futureTask.get(timeout, TimeUnit.MILLISECONDS);} catch (InterruptedException | ExecutionException e) {e.printStackTrace();futureTask.cancel(true);throw e;}catch(TimeoutException e){futureTask.cancel(true);callable.getFlag().waitForEnd();if(callable.getFlag().isNormaled()){return true;}e.printStackTrace();//超时重试retryTimes--;if(retryTimes > 0){Thread.sleep(interval);execute(callable,timeout,interval,retryTimes);}else{throw e;}}return result;} }
四、给出一个调用代码。实现一个继承自BaseFutureTask的 FutureTask任务。依旧需要注意子线程涉及到spring的组件,最好是参数从主线程注入到子线程。
RetryUtil.execute(new SyncProductTask(productBiz,productInfo),timeout,interval,3);
参考文章
https://www.jianshu.com/p/55221d045f39