标签：流程 his use star sys nts ESS pack 适合
实现线程范围的共享变量。
JDK提供了ThreadLocal在一个线程内传递同一个对象
方法调用一定是同一个线程执行的
ThreadLocal一定要在finally中清除：因为当前线程执行完后有可能重新放入线程池中
可以把TheadLocal看成是全局Map<Thread，Object>：
（1）每个线程获取ThradLocal变量时，使用Thread自身作为Key
（2）ThreadLocal表示线程的“局部变量”，它确保每个线程的ThradLocal变量都是独立的
（3）ThreadLocal适合在一个线程的处理流程中保持上下文（避免同一参数在所有方法中传递）
（4）使用ThreadLocal要用try catch finally结构
package com.xuefei.util; public class ThreadLocalTest { //创建一个ThreadLocal对象 static ThreadLocal<String> threadLocal = new ThreadLocal<String>(); public static void main(String[] args) { //通过set方法给当前线程绑定一个指定的值 threadLocal.set("Bob"); //通过get方法随时获取到绑定的值 String current = threadLocal.get(); String current2 = threadLocal.get(); System.out.println(current); System.out.println(current2); //最后通过remove将变量从当前线程解除 threadLocal.remove(); } }
咱们来看个例子：看一下线程中对象的传递
package com.xuefei.util; public class User { //用户名 String name; //用户级别 int level; //构造方法注入 public User(String name, int level) { this.name = name; this.level = level; } } class UserContext implements AutoCloseable { //定义全局唯一变量 static final ThreadLocal<User> context = new ThreadLocal<User>(); //获取当前线程的ThreadLocal.User; public static User getCurrentUser() { return context.get(); } //初始化ThreadLocal的User public UserContext(User user) { context.set(user); } //移除ThreadLocal关联的User public void close() throws Exception { context.remove(); } } class ProcessThread extends Thread { //声明Us对象类型 User user; //构造方法注入User public ProcessThread(User user) { this.user = user; } public void run() { //线程注入user try (UserContext ctx = new UserContext(user)) { //调用方法 new Greeting().hello(); Level.checkLevel(); } catch (Exception e) { e.printStackTrace(); } } } class Greeting { void hello() { //获取当前线程对象 User user = UserContext.getCurrentUser(); System.out.println("Hello, " + user.name+"!"); } } class Level { static void checkLevel() { //获取当前线程对象 User user = UserContext.getCurrentUser(); if(user.level > 100) { System.out.println(user.name + "is a VIP user"); } } }
package com.xuefei.util; public class Main { public static void main(String[] args) throws InterruptedException { Thread t1 = new ProcessThread(new User("Bob",120)); Thread t2 = new ProcessThread(new User("Alice",98)); t1.start(); t2.start(); t1.join(); t2.join(); System.out.println("Main end"); } }
运行结果
标签：流程 his use star sys nts ESS pack 适合
原文地址：https://www.cnblogs.com/lililixuefei/p/11904410.html
