Java ThreadFactory接口用法

根據需要創建新線程的對象。使用線程工廠就無需再手工編寫對 new Thread 的調用了，從而允許應用程序使用特殊的線程子類、屬性等等。

 

JDK中的介紹：

An object that creates new threads on demand. Using thread factories removes hardwiring of calls tonew Thread, enabling applications to use special thread subclasses, priorities, etc.

The simplest implementation of this interface is just:

 

class SimpleThreadFactory implements ThreadFactory {  
  public Thread newThread(Runnable r) {  
    return new Thread(r);  
  }  
}  

 

 

The  Executors.defaultThreadFactory method provides a more useful simple implementation, that sets the created thread context to known values before returning it. 

　　/** 
     * The default thread factory 
     */  
    static class DefaultThreadFactory implements ThreadFactory {  
        static final AtomicInteger poolNumber = new AtomicInteger(1);  
        final ThreadGroup group;  
        final AtomicInteger threadNumber = new AtomicInteger(1);  
        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;  
        }  
    }  

 

下面寫一簡單示例。

 

package com.test;  
  
import java.util.concurrent.ExecutorService;  
import java.util.concurrent.Executors;  
import java.util.concurrent.ThreadFactory;  
  
class Task implements Runnable{  
    int taskId;  
    public Task(int taskId) {  
        this.taskId=taskId;  
    }  
      
    @Override  
    public void run() {  
        System.out.println(Thread.currentThread().getName()+"--taskId: "+taskId);  
          
    }  
}  
  
class DaemonThreadFactory implements ThreadFactory {  
    @Override  
    public Thread newThread(Runnable r) {  
        Thread t=new Thread(r);  
        t.setDaemon(true);  
        return t;  
    }  
      
}  
public class ThreadFactoryTest {  
    public static void main(String[] args) {  
        ExecutorService exec=Executors.newFixedThreadPool(3,new DaemonThreadFactory());  
        for(int i=0;i<3;i++) {  
            exec.submit(new Task(i));  
        }  
        exec.shutdown();  
    }  
}  

 

輸出如下：

 

Thread-0--taskId: 0
Thread-1--taskId: 1
Thread-2--taskId: 2

 

分析：

DaemonThreadFactory中覆寫的newThread()方法與submit()方法的調用關系，也就是說DaemonThreadFactory是如何起作用的。

調試輸出其調用關系：

 

也就是說，submit()時會調用DaemonThreadFactory類的newThread()方法來創建線程。