4、线程范围内的数据共享之ThreadLocal

/**
 * 线程范围类的数据共享
 * 核心：ThreadLocal类
 * 实际场景：
 * Hibernate的getCurrentSession方法，就是从线程范围内获取存在的session,如果不存在则新建一个并绑定到线程上
 * struts将一个请求里的所有参数绑定到一个线程范围内的对象里
 * @author yzl
 *
 */
public class ThreadPart_4 {
    public static void main(String[] args) {
        new Thread(new Runnable() {
            public void run() {
                MyThreadLocalObj obj = MyThreadLocalObj.getInstance();
                while(obj.getData()<20){
                    obj.add();
                    System.out.println(Thread.currentThread().getName() + " after add method value :" + obj.getData());
                    //这里操作其实就是同一个MyThreadLocalObj对象
                    new MyAdd().add();
                    System.out.println(Thread.currentThread().getName() + " after MyAdd add method value :" + obj.getData());
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
        
        new Thread(new Runnable() {
            public void run() {
                MyThreadLocalObj obj = MyThreadLocalObj.getInstance();
                while(obj.getData()>0){
                    obj.sub();
                    System.out.println(Thread.currentThread().getName() + " after sub method value :" + obj.getData());
                    //这里操作其实就是同一个MyThreadLocalObj对象
                    new MySub().sub();
                    System.out.println(Thread.currentThread().getName() + " after MySub sub method value :" + obj.getData());
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }
}

class MyAdd{
    public void add(){
        MyThreadLocalObj.getInstance().add();
    }
}

class MySub{
    public void sub(){
        MyThreadLocalObj.getInstance().sub();
    }
}

/**
 * 单例模式下的
 * 线程范围内共享 
 * 线程范围外互不影响
 * @author yzl
 *
 */
class MyThreadLocalObj{
    private int data = 10;
    
    public void add(){
        data++;
    }
    
    public void sub(){
        data--;
    }
    
    private MyThreadLocalObj(){};
    private static ThreadLocal<MyThreadLocalObj> local = new ThreadLocal<MyThreadLocalObj>();
    
    
    public static MyThreadLocalObj getInstance(){
        if(local.get() == null){
            local.set(new MyThreadLocalObj());
        }
        return local.get();
    }

    public int getData() {
        return data;
    }
}

运行结果：

不同线程操作的对象不是同一个，同一个线程操作的是同一个

 1 Thread-0 after add method value :11
 2 Thread-1 after sub method value :9
 3 Thread-0 after MyAdd add method value :12
 4 Thread-1 after MySub sub method value :8
Thread-1 after sub method value :7
Thread-0 after add method value :13
Thread-1 after MySub sub method value :6
Thread-0 after MyAdd add method value :14
Thread-1 after sub method value :5
Thread-0 after add method value :15
Thread-1 after MySub sub method value :4
Thread-0 after MyAdd add method value :16
Thread-0 after add method value :17
Thread-1 after sub method value :3
Thread-0 after MyAdd add method value :18
Thread-1 after MySub sub method value :2
Thread-0 after add method value :19
Thread-0 after MyAdd add method value :20
Thread-1 after sub method value :1
Thread-1 after MySub sub method value :0