专业的网站制作团队,随州网站,个人网站做团购,重庆市建设特种信息线程池在提交的任务在处理过程中发生了异常#xff0c;却没有捕获到#xff0c;导致异常只是输出在控制台#xff0c;这通常需要把异常记录下来1、通过观察ThreadGroup的构造方法知道#xff0c;当调用线程组的构造方法时#xff0c;会获取当前线程所属的线程组#xff0…
线程池在提交的任务在处理过程中发生了异常却没有捕获到导致异常只是输出在控制台这通常需要把异常记录下来1、通过观察ThreadGroup的构造方法知道当调用线程组的构造方法时会获取当前线程所属的线程组作为当前正在创建的线程组的parent线程组。2、通过在main方法中获取线程组信息可知当前main线程所属的线程组是main线程组而main线程组的parent线程组是system线程组。3、ThreadGroup的uncaughtException实现如下
public void uncaughtException(Thread t, Throwable e) {if (parent ! null) {parent.uncaughtException(t, e);} else {Thread.UncaughtExceptionHandler ueh Thread.getDefaultUncaughtExceptionHandler();if (ueh ! null) {ueh.uncaughtException(t, e);} else if (!(e instanceof ThreadDeath)) {/* 【异常输出信息的红色是这里输出来的】 */System.err.print(Exception in thread \ t.getName() \ );e.printStackTrace(System.err);}}}4、Thread类有个dispatchUncaughtException方法当Thread线程运行run方法时异常抛出来而没有处理时将会把异常抛给虚拟机虚拟机将会交给该Thread对象的dispatchUncaughtException方法处理可以从如下代码看到如果没有给Thread设置具体的UncaughtExceptionHandler将会给线程组处理而线程组一直委托给parent处理所以最后到了system线程组处理由于它的parent是null所以就使用System.err输出了异常信息
private void dispatchUncaughtException(Throwable e) {getUncaughtExceptionHandler().uncaughtException(this, e);
}
public UncaughtExceptionHandler getUncaughtExceptionHandler() {return uncaughtExceptionHandler ! null ?uncaughtExceptionHandler : group;
}5、线程池中默认的DefaultThreadFactory的实现如下
static class DefaultThreadFactory implements ThreadFactory {private static final AtomicInteger poolNumber new AtomicInteger(1);private final ThreadGroup group;private final AtomicInteger threadNumber new AtomicInteger(1);private final String namePrefix;DefaultThreadFactory() {SecurityManager s System.getSecurityManager();/* 交给的是当前线程所属的线程组 */group (s ! null) ? s.getThreadGroup() :Thread.currentThread().getThreadGroup();namePrefix pool- poolNumber.getAndIncrement() -thread-;}public Thread newThread(Runnable r) {/* 创建的线程 所指定的线程组是在构造方法中设置的 */Thread t new Thread(group, r,namePrefix threadNumber.getAndIncrement(),0);if (t.isDaemon())t.setDaemon(false);if (t.getPriority() ! Thread.NORM_PRIORITY)t.setPriority(Thread.NORM_PRIORITY);return t;}
}测试
public class ThrTask implements Runnable {private int a, b;private ThrTask(int a, int b) {this.a a;this.b b;}Overridepublic void run() {double re a / b;System.out.println(re);}public static void main(String[] args) {ThreadPoolExecutor threadPoolExecutor new ThreadPoolExecutor(0, Integer.MAX_VALUE, 1, TimeUnit.SECONDS, new SynchronousQueue(), new ThreadFactory() {Overridepublic Thread newThread(Runnable r) {Thread t new Thread(Thread.currentThread().getThreadGroup(), r, myThread);if (t.isDaemon()) t.setDaemon(false);t.setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {Overridepublic void uncaughtException(Thread t, Throwable e) {System.out.println(线程 t.getName() 出现异常 e);// record this self..}});return t;}});for (int i 0; i 5; i) {//将不会抛出异常// threadPoolExecutor.submit(new ThrTask(5, i));//将会抛出异常threadPoolExecutor.execute(new ThrTask(5, i));}}
}
