java缓存(2、ThreadLocal<T>)

程序图

描述

ThreadCache类是ThreadLocal<T>类的封装，UserManagerServlet请求方法里面创建一个User对象，然后，将对象放到ThreadLocal中，然后，从UserManagerDao获得该对象，再返回给Servlet

程序

ThreadCache

package com.tgb.util;

import com.tgb.entity.User;

public class ThreadCache {
	private static ThreadLocal<User> threadLocal;
	static {
		threadLocal= new ThreadLocal<User>();
	}
	public static User getUser(){
		return threadLocal.get();
	}
	public static void setUser(User user){
		threadLocal.set(user);
	}
}

Servlet

package com.tgb.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.tgb.entity.User;
import com.tgb.service.UserManagerService;
import com.tgb.util.ThreadCache;

public class UserManagerServlet extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doPost(request,response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		int id = Integer.parseInt(request.getParameter("id"));
		String name = request.getParameter("name");
		String password = request.getParameter("password");
		
		User user = new User();
		user.setId(id);
		user.setName(name);
		user.setPassword(password);
		ThreadCache.setUser(user);
		
		UserManagerService userManagerService = new UserManagerService();
		User getUser = userManagerService.getUser();
		System.out.println(getUser);
		
	    response.sendRedirect(request.getContextPath() + "/index.jsp");
	}
}

Dao

package com.tgb.dao;

import com.tgb.entity.User;
import com.tgb.util.ThreadCache;

public class UserDao {
	public User getUser(){
		return ThreadCache.getUser();
	}
}

增强版Demo

概述

对于上面的demo，非常的简单，主要是让大家了解ThreadLocal的功能，其在项目中真正的用途是存储Connection，从达到Service管理事务的目的，下面将给大家介绍一个比较好的demo。

类图概要

描述

ConnectionContext是数据库连接对象池，使用的是c3p0；
ConnectionPoolManager是ThreadLocal<T>的封装；
TransactionManager是事务的封装；
Filter过滤请求，开启事务，调用Servlet，最后，Filter提交事务；
BaseDao使用泛型和反射，实现简单的ORM思想，使程序操作的都是对象；

总结

demo2里面知识点挺多的，是一个比较全面的例子，分页封装，json封装，ThreadLocal，c3p0，事务应用，反射和泛型，自定义注解(demo，没有应用到项目里)，有兴趣的可以下载源码看看，这里不做过多介绍。