首先，创建MyThreadLocal类，区分开java.lang.ThreadLocal

package com.huhu.threadlocal;import java.util.HashMap;
import java.util.Map;public class MyThreadLocal {/*** 所有需要和当前线程绑定的数据要放到这个容器当中*/private Map map = new HashMap<>();/*** 向ThreadLocal中绑定数据*/public void set(T obj) {map.put(Thread.currentThread(), obj);}/*** 从ThreadLocal中获取数据** @return*/public T get() {return map.get(Thread.currentThread());}/*** 移除ThreadLocal当中的数据*/public void remove() {map.remove(Thread.currentThread());}
}

 接着，分别创建Connection类和DBUtil类

package com.huhu.threadlocal;public class Connection {
}

package com.huhu.threadlocal;public class DBUtil {//静态变量特点：类加载时执行，并且只执行一次private static MyThreadLocal local=new MyThreadLocal<>();/*** 调用方法获取Connection对象* @return*/public static Connection getConnection(){Connection connection=local.get();if (connection==null){//第一次调用方法肯定为null，new一个connection=new Connection();//将new出来的Connection对象绑定到Map集合中local.set(connection);}return connection;}}

然后创建UserDao类和UserService类

package com.huhu.threadlocal;public class UserDao {public void insert() {Thread thread=Thread.currentThread();System.out.println(thread);Connection connection = DBUtil.getConnection();System.out.println(connection);System.out.println("User Dao insert...");}
}

package com.huhu.threadlocal;public class UserService {private UserDao userDao = new UserDao();public void save() {Thread thread=Thread.currentThread();System.out.println(thread);Connection connection = DBUtil.getConnection();System.out.println(connection);userDao.insert();}
}

最后，创建测试Test类

package com.huhu.threadlocal;
//张三发送请求，对应一个线程t1
//李四发送请求，对应一个线程t2
public class Test {public static void main(String[] args) {Thread thread=Thread.currentThread();System.out.println(thread);//Connection connection=new Connection();UserService userService=new UserService();userService.save();}
}