Java線程池執(zhí)行過(guò)程中遇到異常的原因和解決辦法

更新時(shí)間：2025年10月11日 09:38:52 作者：程序員小假

當(dāng)線程池中線程頻繁出現(xiàn)未捕獲的異常,那線程的復(fù)用率就大大降低了,需要不斷地創(chuàng)建新線程,所以本文通過(guò)詳細(xì)的代碼給大家介紹了Java線程池執(zhí)行過(guò)程中遇到異常的解決辦法,需要的朋友可以參考下

線程遇到未處理的異常就結(jié)束了

這個(gè)好理解，當(dāng)線程出現(xiàn)未捕獲異常的時(shí)候就執(zhí)行不下去了，留給它的就是垃圾回收了。

線程池中線程頻繁出現(xiàn)未捕獲異常

當(dāng)線程池中線程頻繁出現(xiàn)未捕獲的異常，那線程的復(fù)用率就大大降低了，需要不斷地創(chuàng)建新線程。
做個(gè)實(shí)驗(yàn)：

public class ThreadExecutor {
    private ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
                                                                           new ArrayBlockingQueue<>(200), new ThreadFactoryBuilder().setNameFormat("customThread %d").build());
    @Test
    public void test() {
        IntStream.rangeClosed(1, 5).forEach(i -> {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            threadPoolExecutor.execute(() -> {
                int j = 1/0;
            });});
    }
}

新建一個(gè)只有一個(gè)線程的線程池，每隔0.1s提交一個(gè)任務(wù)，任務(wù)中是一個(gè)1/0的計(jì)算。

Exception in thread "customThread 0" java.lang.ArithmeticException: / by zero
 at thread.ThreadExecutor.lambda$null$0(ThreadExecutor.java:25)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "customThread 1" java.lang.ArithmeticException: / by zero
 at thread.ThreadExecutor.lambda$null$0(ThreadExecutor.java:25)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "customThread 2" java.lang.ArithmeticException: / by zero
 at thread.ThreadExecutor.lambda$null$0(ThreadExecutor.java:25)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "customThread 3" java.lang.ArithmeticException: / by zero
 at thread.ThreadExecutor.lambda$null$0(ThreadExecutor.java:25)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "customThread 4" java.lang.ArithmeticException: / by zero
 at thread.ThreadExecutor.lambda$null$0(ThreadExecutor.java:25)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)
Exception in thread "customThread 5" java.lang.ArithmeticException: / by zero
 at thread.ThreadExecutor.lambda$null$0(ThreadExecutor.java:25)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
 at java.lang.Thread.run(Thread.java:748)

可見(jiàn)每次執(zhí)行的線程都不一樣，之前的線程都沒(méi)有復(fù)用。原因是因?yàn)槌霈F(xiàn)了未捕獲的異常。
把異常捕獲試試：

public class ThreadExecutor {
    private ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
                                                                           new ArrayBlockingQueue<>(200), new ThreadFactoryBuilder().setNameFormat("customThread %d").build());
    @Test
    public void test() {
        IntStream.rangeClosed(1, 5).forEach(i -> {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            threadPoolExecutor.execute(() -> {
                try {
                    int j = 1 / 0;
                } catch (Exception e) {
                    System.out.println(Thread.currentThread().getName() +" "+ e.getMessage());
                }
            });
        });
    }
}

customThread 0 / by zero
customThread 0 / by zero
customThread 0 / by zero
customThread 0 / by zero
customThread 0 / by zero

可見(jiàn)當(dāng)異常捕獲了，線程就可以復(fù)用了。

問(wèn)題來(lái)了，代碼中異常不可能全部捕獲

如果要捕獲那些沒(méi)被業(yè)務(wù)代碼捕獲的異常，可以設(shè)置Thread類的uncaughtExceptionHandler屬性。這時(shí)使用ThreadFactoryBuilder會(huì)比較方便，ThreadFactoryBuilder是guava提供的ThreadFactory生成器。

new ThreadFactoryBuilder()
    .setNameFormat("customThread %d")
    .setUncaughtExceptionHandler((t, e) -> System.out.println(t.getName() + "發(fā)生異常" + e.getCause()))
    .build()

修改之后：

public class ThreadExecutor {
    private static ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
                                                                                  new ArrayBlockingQueue<>(200),
                                                                                  new ThreadFactoryBuilder()
                                                                                  .setNameFormat("customThread %d")
                                                                                  .setUncaughtExceptionHandler((t, e) -> System.out.println("UncaughtExceptionHandler捕獲到：" + t.getName() + "發(fā)生異常" + e.getMessage()))
                                                                                  .build());
    @Test
    public void test() {
        IntStream.rangeClosed(1, 5).forEach(i -> {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            threadPoolExecutor.execute(() -> {
                System.out.println("線程" + Thread.currentThread().getName() + "執(zhí)行");
                int j = 1 / 0;
            });
        });
    }
}

線程customThread 0執(zhí)行
UncaughtExceptionHandler捕獲到：customThread 0發(fā)生異常/ by zero
線程customThread 1執(zhí)行
UncaughtExceptionHandler捕獲到：customThread 1發(fā)生異常/ by zero
線程customThread 2執(zhí)行
UncaughtExceptionHandler捕獲到：customThread 2發(fā)生異常/ by zero
線程customThread 3執(zhí)行
UncaughtExceptionHandler捕獲到：customThread 3發(fā)生異常/ by zero
線程customThread 4執(zhí)行
UncaughtExceptionHandler捕獲到：customThread 4發(fā)生異常/ by zero

可見(jiàn)，結(jié)果并不是想象的那樣，線程池中原有的線程沒(méi)有復(fù)用！所以通過(guò)UncaughtExceptionHandler想將異常吞掉使線程復(fù)用這招貌似行不通。它只是做了一層異常的保底處理。
將excute改成submit試試

public class ThreadExecutor {
    private static ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(1, 1, 60, TimeUnit.SECONDS,
                                                                                  new ArrayBlockingQueue<>(200),
                                                                                  new ThreadFactoryBuilder()
                                                                                  .setNameFormat("customThread %d")
                                                                                  .setUncaughtExceptionHandler((t, e) -> System.out.println("UncaughtExceptionHandler捕獲到：" + t.getName() + "發(fā)生異常" + e.getMessage()))
                                                                                  .build());
    @Test
    public void test() {
        IntStream.rangeClosed(1, 5).forEach(i -> {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            Future<?> future = threadPoolExecutor.submit(() -> {
                System.out.println("線程" + Thread.currentThread().getName() + "執(zhí)行");
                int j = 1 / 0;
            });
            try {
                future.get();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        });
    }
}

線程customThread 0執(zhí)行
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
線程customThread 0執(zhí)行
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
線程customThread 0執(zhí)行
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
線程customThread 0執(zhí)行
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
線程customThread 0執(zhí)行
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero

通過(guò)submit提交線程可以屏蔽線程中產(chǎn)生的異常，達(dá)到線程復(fù)用。當(dāng)get()執(zhí)行結(jié)果時(shí)異常才會(huì)拋出。
原因是通過(guò)submit提交的線程，當(dāng)發(fā)生異常時(shí)，會(huì)將異常保存，待future.get();時(shí)才會(huì)拋出。
這是Futuretask的部分run()方法，看setException：

public void run() {
    try {
        Callable<V> c = callable;
        if (c != null && state == NEW) {
            V result;
            boolean ran;
            try {
                result = c.call();
                ran = true;
            } catch (Throwable ex) {
                result = null;
                ran = false;
                setException(ex);
            }
            if (ran)
                set(result);
        }
    } 
}
protected void setException(Throwable t) {
    if (UNSAFE.compareAndSwapInt(this, stateOffset, NEW, COMPLETING)) {
        outcome = t;
        UNSAFE.putOrderedInt(this, stateOffset, EXCEPTIONAL); // final state
        finishCompletion();
    }
}

將異常存在outcome對(duì)象中，沒(méi)有拋出，再看get方法：

public V get() throws InterruptedException, ExecutionException {
    int s = state;
    if (s <= COMPLETING)
        s = awaitDone(false, 0L);
    return report(s);
}
private V report(int s) throws ExecutionException {
    Object x = outcome;
    if (s == NORMAL)
        return (V)x;
    if (s >= CANCELLED)
        throw new CancellationException();
    throw new ExecutionException((Throwable)x);
}

當(dāng)outcome是異常時(shí)才拋出。

總結(jié)

1、線程池中線程中異常盡量手動(dòng)捕獲

2、通過(guò)設(shè)置ThreadFactory的UncaughtExceptionHandler可以對(duì)未捕獲的異常做保底處理，通過(guò)execute提交任務(wù)，線程依然會(huì)中斷，而通過(guò)submit提交任務(wù)，可以獲取線程執(zhí)行結(jié)果，線程異常會(huì)在get執(zhí)行結(jié)果時(shí)拋出。

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