ThreadLocal深入研究-spring

request作用域的Bean、事务管理、任务调度、AOP等模块共享变量的思想及源代码的实现：

// 共享数据的公共接口
interface TopInterface {
	ThreadLocal<String> threadLocal = new ThreadLocal<String>();// 三层共享的线程变量
}

class TestDao implements TopInterface {
	
	public void save(String name) {
		if(null == threadLocal.get()) 
			threadLocal.set(name);
	}
	
	public String find() {
		return threadLocal.get();
	}
}

class TestServiceImpl implements TopInterface {
	private TestDao dao = new TestDao();
	
	public void save(String name) {
		dao.save(name);
	}
	
	public String find() {
		return threadLocal.get();
	}
}

class TestActionImpl implements TopInterface {
	private TestServiceImpl service = new TestServiceImpl();
	
	public void save(String name) {
		service.save(name);
	}
	
	public String find() {
		return threadLocal.get();
	}
}

 

测试代码：

public static void main(String[] args) {
		TestActionImpl action = new TestActionImpl();
		action.save("张三");
		
		TestDao dao = new TestDao();
		System.out.println("hello : " + dao.find() + ", 这是dao层");
		
		TestServiceImpl service = new TestServiceImpl();
		System.out.println("hello : " + service.find() + ", 这是service层");
		
		System.out.println("hello : " + action.find() + ", 这是action层");
		
	}

 

输出结果：

hello : 张三, 这是dao层
hello : 张三, 这是service层
hello : 张三, 这是action层

该变量在多线程环境下是线程安全的，其起重要的还是ThreadLocal。