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