线程范围内数据共享

用处：处理数据库中事务管理器较为常用，所有的操作都是针对同一份数据。系统角度进行开发编程。

 

第一种方法，这种方法比较粗糙

public class ThreadScopeShareData { private static int data = 0; private static Map<Thread , Integer> threadData = new HashMap<Thread,Integer>(); public static void main(String[] args){ for (int i = 0; i < 2; i++) { new Thread(new Runnable(){ public void run(){ data = new Random().nextInt(); System.out.println(Thread.currentThread().getName() + " has put data :"+data); threadData.put(Thread.currentThread(),data); new A().get(); new B().get(); } }).start(); } } static class A{ public void get(){ data = threadData.get(Thread.currentThread()); System.out.println("A from "+ Thread.currentThread().getName()+" get data :"+data); } } static class B{ public void get(){ data = threadData.get(Thread.currentThread()); System.out.println("B from "+ Thread.currentThread().getName()+" get data :"+data); } } }

 

 

 

 

 

 

第二种方法：ThreadLocal，该类相当于一个Map

public class ThreadLocalTest { static final ThreadLocal<Integer> x = new ThreadLocal<Integer>(); public static void main(String[] args){ for (int i = 0; i < 2; i++) { new Thread(new Runnable(){ public void run(){ int data = new Random().nextInt()/10000000; System.out.println(Thread.currentThread().getName() + " has put data :"+data); x.set(data); new A().get(); new B().get(); } }).start(); } } static class A{ public void get(){ int data = x.get(); System.out.println("A from "+ Thread.currentThread().getName()+" get data :"+data); } } static class B{ public void get(){ int data = x.get(); System.out.println("B from "+ Thread.currentThread().getName()+" get data :"+data); } } }

 

第三种方法：操作多个数据，不单单是基本数据类型。可以整合成一个实体对象，然后往ThreadLocal中set这个对象。

public class ThreadLocalTest { private static final ThreadLocal<Integer> x = new ThreadLocal<Integer>(); private static final ThreadLocal<MyThreadScopeData> myThreadScopeData = new ThreadLocal<MyThreadScopeData>(); public static void main(String[] args){ for (int i = 0; i < 2; i++) { new Thread(new Runnable(){ public void run(){ int data = new Random().nextInt()/10000000; System.out.println(Thread.currentThread().getName() + " has put data :"+data); x.set(data); MyThreadScopeData myData = new MyThreadScopeData(); myData.setName(" name "+data); myData.setAge(data); myThreadScopeData.set(myData); new A().get(); new B().get(); } }).start(); } } static class A{ public void get(){ int data = x.get(); System.out.println("A from "+ Thread.currentThread().getName()+" get data :"+data); MyThreadScopeData myData = myThreadScopeData.get(); System.out.println("A from "+ Thread.currentThread().getName()+" getMydata :"+myData.getName()+","+myData.getAge()); } } static class B{ public void get(){ int data = x.get(); System.out.println("B from "+ Thread.currentThread().getName()+" get data :"+data); MyThreadScopeData myData = myThreadScopeData.get(); System.out.println("B from "+ Thread.currentThread().getName()+" getMydata :"+myData.getName()+","+myData.getAge()); } } } class MyThreadScopeData{ private String name; private int age; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }

 

第四种方式：很优雅的处理办法，仿单例模式处理。ThradLocal类放到实体类的背后了，设计也交给了实体类，调用者不需要关心实体类的设计，只需要get到实体类的实例对象即可，同一线程内，任何地方调用实体类的实例对象，都是同一个实例对象，操作的数据都是同一份，也就达到了线程内数据共享的效果。该处理方法很好的体现了面向对象的思想。

strust2也是如此的设计方式。

public class ThreadLocalTest { private static final ThreadLocal<Integer> x = new ThreadLocal<Integer>(); private static final ThreadLocal<MyThreadScopeData> myThreadScopeData = new ThreadLocal<MyThreadScopeData>(); public static void main(String[] args){ for (int i = 0; i < 2; i++) { new Thread(new Runnable(){ public void run(){ int data = new Random().nextInt()/10000000; System.out.println(Thread.currentThread().getName() + " has put data :"+data); x.set(data); MyThreadScopeData.getThreadInstance().setName(" name "+data); MyThreadScopeData.getThreadInstance().setAge(data); new A().get(); new B().get(); } }).start(); } } static class A{ public void get(){ int data = x.get(); System.out.println("A from "+ Thread.currentThread().getName()+" get data :"+data); MyThreadScopeData myData = MyThreadScopeData.getThreadInstance(); System.out.println("A from "+ Thread.currentThread().getName()+" getMydata :"+myData.getName()+","+myData.getAge()); } } static class B{ public void get(){ int data = x.get(); System.out.println("B from "+ Thread.currentThread().getName()+" get data :"+data); MyThreadScopeData myData = MyThreadScopeData.getThreadInstance(); System.out.println("B from "+ Thread.currentThread().getName()+" getMydata :"+myData.getName()+","+myData.getAge()); } } } class MyThreadScopeData{ private MyThreadScopeData(){}; private static ThreadLocal<MyThreadScopeData> map = new ThreadLocal<MyThreadScopeData>(); public static MyThreadScopeData getThreadInstance(){ MyThreadScopeData instance = map.get(); if(instance == null){ instance = new MyThreadScopeData(); map.set(instance); } return instance; } private String name; private int age; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }

 

使用ThreadLocal类：

       类似于一种栈机制，不同的线程在其有不同的记录，当时间一久，越积越多，提供clean（）方法供清理。当然其内部可以自动进行回收，不用担心如果自己不处理会溢出问题。线程一完成，则会自动回收对应的实例对象的引用。如果不同的ThreadLocal对象中，同一线程有记录，则当该线程处理完后，这些不同的ThreadLocal对象中的记录都会被回收，除非该线程对应的实例对象有其他的线程所关联操作。详细查询jdk文档。

 

提问：如何控制线程死亡状态？