java并发编程ThreadLocal的使用

红太狼 2022-07-21 00:29 127阅读 0赞

ThreadLocal与synchronized 有着相反的概念，前者在多线程使用时会创建新的对象，后者保证对象在多线程是唯一的。

看代码好理解：

public class Test {
        ThreadLocal<Long> longLocal = new ThreadLocal<Long>();
        ThreadLocal<String> stringLocal = new ThreadLocal<String>();
    
    
        public void set() {
            longLocal.set(Thread.currentThread().getId());
            stringLocal.set(Thread.currentThread().getName());
        }
    
        public long getLong() {
            return longLocal.get();
        }
    
        public String getString() {
            return stringLocal.get();
        }
    
        public static void main(String[] args) throws InterruptedException {
            final Test test = new Test();
    
    
            test.set();
            System.out.println(test.getLong());
            System.out.println(test.getString());
    
    
            Thread thread1 = new Thread(){
                public void run() {
                    test.set();
                    System.out.println(test.getLong());
                    System.out.println(test.getString());
                };
            };
            thread1.start();
            thread1.join();
    
            System.out.println(test.getLong());
            System.out.println(test.getString());
        }
    }

[博客出处][Link 1]  
运行结果:

1
    main
    8
    Thread-0
    1
    main

final的test对象，在新线程中，set之后，根据线程重新对变量进行了赋值。

推荐用法：

private static ThreadLocal<Connection> connectionHolder = new ThreadLocal<Connection>() {
        public Connection initialValue() {
            return DriverManager.getConnection(DB_URL);
        }
    };
    
    
    //不同线程，拿到的connection是不一样的
    public static Connection getConnection() {
        return connectionHolder.get();
    }

参考：[http://www.cnblogs.com/dolphin0520/p/3920407.html][http_www.cnblogs.com_dolphin0520_p_3920407.html]

[Link 1]: http://georgeyang.cn
[http_www.cnblogs.com_dolphin0520_p_3920407.html]: http://www.cnblogs.com/dolphin0520/p/3920407.html