fescar源码分析-NamedThreadFactory

在java的并发包中java.util.concurrent已经有很多线程池的实现，所有线程池的实现都实现于java.util.concurrent接口：

ExecutorService.png

在fescar中直接并最常使用到的线程池有：

ThreadPoolExecutor ：最核心的线程池实现。

ScheduledThreadPoolExecutor ：继承于ThreadPoolExecutor，主要用来在给定的延迟之后运行任务或者定期执行任务。

所有线程池都可以传入一个java.util.concurrent.ThreadFactory接口的线程工厂实现类。如果不传会使用一个默认工厂类，如：

    public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue workQueue) {
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), defaultHandler);

所有的线程工厂类需要实现java.util.concurrent.ThreadFactory接口，默认的线程工厂实现类的线程名称是以"pool-"为前缀，中间一个序列码，"-thread-"为后缀。

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;
        }
    }

在fescar中使用了很多的线程池，如果所有线程名称都是这种名称，比较难于调试与监控。所以需要自定义线程工厂类，可以定义线程名称。所以就实现了一个NamedThreadFactory：

public class NamedThreadFactory implements ThreadFactory
{
    private static final AtomicInteger POOL_SEQ = new AtomicInteger(1);
    private final AtomicInteger mThreadNum = new AtomicInteger(1);
    private final String mPrefix;
    private final boolean mDaemo;
    private final ThreadGroup mGroup;
    public NamedThreadFactory()
    {
        this("pool-" + POOL_SEQ.getAndIncrement(),false);
    }
    public NamedThreadFactory(String prefix)
    {
        this(prefix,false);
    }
    public NamedThreadFactory(String prefix,boolean daemo)
    {
        mPrefix = prefix + "-thread-";
        mDaemo = daemo;
        SecurityManager s = System.getSecurityManager();
        mGroup = ( s == null ) ? Thread.currentThread().getThreadGroup() : s.getThreadGroup();
    }
    public Thread newThread(Runnable runnable)
    {
        String name = mPrefix + mThreadNum.getAndIncrement();
        Thread ret = new Thread(mGroup,runnable,name,0);
        ret.setDaemon(mDaemo);
        return ret;
    }
    public ThreadGroup getThreadGroup()
    {
        return mGroup;
    }
}

从代码中可以看到，如果创建NamedThreadFactory实例时，如果传入线程名称前缀，如：

new NamedThreadFactory("RetryRollbacking", 1)

名称将为：

RetryRollbacking-thread-${NUMBER}

如果不传入线程名称，则默认为：

pool-${NUMBER}-thread