ThreadLocal在多线程中的应用

 

本例充分演示了ThreadLocal在多线程环境下，与线程绑定后的数据操作是完全隔离的！

放心使用ThreadLocal吧！千万记得用完之后要remove!

 

 

package thread;

import java.util.Date;
import java.util.Random;

/**
 * 线程范围内的变量，每个线程都有自己的一份数据，换不干扰
 * 
 * 原理：
 * ThreadLocal类中通过Map<Thread.currentThread(), Object>实现数据与线程绑定的！
 * Map的key就是线程自己，所以每个线程都能拿到属于自己的那份数据
 * 
 */
public class ThreadLocalScopeData {
	
	private static ThreadLocal<TreadLocalScopeData> threadLocal = new ThreadLocal<TreadLocalScopeData>();
	
	private ThreadLocalScopeData() {}
	
	//此方法不需要同步
	public static TreadLocalScopeData getThreadLocalBinding() {
		TreadLocalScopeData instance = threadLocal.get();
		if(instance==null) {
			instance = new TreadLocalScopeData();
			threadLocal.set(instance);
		}
		return instance;
	}
	
	//=============================================
	
	Object data1;
	
	Object data2;
	
	// define  more data binding to thread 
	
	public TreadLocalScopeData data1(Object data1) {
		this.data1 = data1;
		return this;
	}
	
	public TreadLocalScopeData data2(Object data2) {
		this.data2 = data2;
		return this;
	}
	
	//finally remove threadLocal variable
	public void remove() {
		threadLocal.remove();
	}
	
	//**************************************************
	//Test
	public static void main(String[] args) {
		for(int i=0;i<10;i++) {
			new Thread(new Runnable() {
				public void run() {
					ThreadLocalScopeData.justSet();
					ThreadLocalScopeData.justGet("before remove");

					//attempt to visit threadLocal data after removed
					TreadLocalScopeData.getThreadLocalBinding().remove();
					TreadLocalScopeData.justGet("after remove");
				}
			}).start();
		}
		
	}
	
	public static void justSet() {
		TreadLocalScopeData treadLocalScopeData = TreadLocalScopeData.getThreadLocalBinding();
		String data1Val = new Date() +", so easy!";
		int data2Val = new Random().nextInt();
		System.out.println(Thread.currentThread().getName()+" set: " + data1Val + ", " + data2Val);
		treadLocalScopeData.data1(data1Val).data2(data2Val);
		try {
			Thread.sleep(new Random().nextInt(100));
		} catch (InterruptedException e) {
			return;
		}
	}
	
	public static void justGet(String when) {
		TreadLocalScopeData treadLocalScopeData = TreadLocalScopeData.getThreadLocalBinding();
		System.out.println(Thread.currentThread().getName()+" get "+ when +":" + treadLocalScopeData.data1 + ", " + treadLocalScopeData.data2);
		try {
			Thread.sleep(new Random().nextInt(100));
		} catch (InterruptedException e) {
			return;
		}
	}
}