Java線程池-線程工廠ThreadFactory

線程工廠ThreadFactory

我們在項目開發額過程中，如果有很多地方使用多線程，那么給線程命名是十分有必要的,這樣當出現問題的時候就比較容易排查

創建線程池，使用默認的線程工廠

    /**
     * 創建線程池
     */
    public static final ThreadPoolExecutor pool =
            new ThreadPoolExecutor(
                    20,
                    100,
                    5,
                    TimeUnit.SECONDS,
                    new ArrayBlockingQueue<>(100)
            );

測試

 public static void main(String[] args) {
        pool.execute(() -> {
            Integer integer = getOrderInfo();
            System.out.println(integer);
        });
        pool.shutdown();
    }

    private static Integer getOrderInfo(){
        try {
            List<Integer> list = new ArrayList<>();
            for (int i = 0 ; i < 10 ; i++){
                list.add(i);
            }
            return list.get(11);
        }catch (Exception e){
            throw new IndexOutOfBoundsException("數組越界");
        }
    }

 

上面程序發生異常，數組下標越界，我們發現線程的名稱是pool-1-thread-1，pool代表是哪一個線程池，如果再啟動一個線程池 就是pool-2,一直按照3,4,5,一直遞增,thread-1則是線程,也是遞增,thread-2,thread-2,但是當我們系統業務復雜，服務很多， 根據這個報錯很難找出是哪里的問題。 

為線程設定名字

我們首先看一下默認的ThreadFactory，

 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();
            group = (s != null) ? s.getThreadGroup() :
                                  Thread.currentThread().getThreadGroup();
            namePrefix = "pool-" +
                          poolNumber.getAndIncrement() +
                         "-thread-";
        }

        public Thread newThread(Runnable r) {
            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;
        }
    }

不難看出在無參構造函數中使用了pool-作為前綴，那么這個我們可以自定義為自己的業務名稱，ThreadFactory是一個接口，我們 實現它，並根據自己的需求去改就行，如下：

我們在構造函數中傳了一個threadName，然后拼接成我們想要的

package thread.customthreadpool.threadFactory;

import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * 自定義線程工廠
 *
 * 線程工廠可以設置線程信息
 */
public class MyThreadFactory 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;

    /**
     * 構造函數傳入我們想業務需要的線程名字threadName，方便發生異常是追溯
     * @param threadName
     */
    public MyThreadFactory(String threadName) {
        SecurityManager s = System.getSecurityManager();
        group = (s != null) ? s.getThreadGroup() :
                Thread.currentThread().getThreadGroup();
        if (threadName == null || threadName.isEmpty()){
            threadName = "pool";
        }
        namePrefix = threadName +
                poolNumber.getAndIncrement() +
                "-thread-";
    }

    public Thread newThread(Runnable r) {
        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;
    }
}

然后將其加入線程池

    /**
     * 創建線程池
     */
    public static final ThreadPoolExecutor pool =
            new ThreadPoolExecutor(
                    20,
                    100,
                    5,
                    TimeUnit.SECONDS,
                    new ArrayBlockingQueue<>(100),
                    new MyThreadFactory("business")
            );

當發生異常時，我們就能清晰的看到是哪一個模塊的問題，能夠快速的去排查