[网络协议] 会话及其会话技术

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[网络协议]会话及其会话技术

会话及其会话技术

1、Cookie对象
cookie是一种会话技术,它用于将会话过程中的数据保存到用户的浏览器中,从而使浏览器和服务器可以更好的地进行数据交互;
（1）通过Cookie技术实现显示用户上次的访问时间功能，退出浏览器在进入时，浏览器会删除cookie对象
实现方法如下：

package cn.com;

import java.io.IOException;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LastAccessServlet
 */
@WebServlet({ "/LastAccessServlet", "/lastAccess" })
public class LastAccessServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.setContentType("text/html;charset=utf-8");
		//response.getWriter().append("Served at: ").append(request.getContextPath());
		
		System.out.println("收到前端请求");
		Cookie[] cookies=request.getCookies();
		String lastTime=null;
		for(int i=0;cookies!=null && i<cookies.length;i++) {
			String name=cookies[i].getName();
			if("lastAccess".equals(name)) {
				lastTime=cookies[i].getValue();
			}
		}
		if(lastTime==null) {
			response.getWriter().print("你是首次访问本网站");
		}
		else {
			response.getWriter().print("你上次的访问时间"+lastTime);
		}
		String time=String.format("%tF<tT", new Date());
		Cookie cookie=new Cookie("lastAccess",time);
		cookie.setMaxAge(60*60*24*7);
		response.addCookie(cookie);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

在这里插入图片描述

2.Session对象:

Cookie技术可以将用户的信息保存在各自的浏览器中,并且可以在多次请求下实现数据的共享,但是,如果传递的信息比较多,使用Cookie技术显然会增大服务器程序处理的难度,这时,可以使用Session技术;

实现购物车:

package cn.com;

import java.io.Serializable;

public class Book implements Serializable{
private static final long serialVersionUIF=1L;
private String id;
private String name;
public Book() {
	
}
public Book(String id,String name) {
this.id=id;
this.name=name;
}
public String getId() {
	return id;
}
public void setId(String id) {
	this.id= id;
}
public String getName() {
	return name;
}
public void setName(String name) {
	this.name= name;
}
}

```创建数据库模拟类:

```c
package cn.com;

import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;

public class BookDB {
	private static Map<String,Book> map = new 	LinkedHashMap<String,Book>();
	static{
		map.put("1", new Book("1","javaWeb"));
		map.put("2", new Book("2","jdbc入门"));
		map.put("3", new Book("3","java基础"));
		map.put("4", new Book("4","struts框架"));
		map.put("5", new Book("5","hibernate框架"));
		
	}
	//1.得到所有图书
	public static Collection<Book> getAll(){
		return map.values();
	}
	//2.根据map的key，也就是图书的id,得到某本图书
	public static Book getBook(String id){
		return map.get(id);
	}		
}

创建一个名为ListBookServlet的类,用于操作单击 “购买” 链接,就可以把书加进购物车;

package cn.com;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Collection;

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

/**
 * Servlet implementation class ListBookServlet
 */
@WebServlet({ "/ListBookServlet", "/listBook" })
public class ListBookServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.setContentType("text/html;charset=utf-8");

		//response.getWriter().append("Served at: ").append(request.getContextPath());
		PrintWriter out=response.getWriter();
        Collection<Book> books=BookDB.getAll();
        out.print("以下是本网站售卖的所有图书："+"<br/><br/>");
        for(Book b:books) {
        String name=b.getName();
        String id=b.getId();
        String url="<a href='/hello3/purcharse?id="+id+"'>点击购买</a>";
        out.print("图书名称："+name+"   "+url+"<br/><br/>");
        }
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

效果如下图所示：
在这里插入图片描述
创建一个名为PurchaseServlet的servlet类,其作用是保存到Session对象中

package cn.com;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class PurchaseServlet
 */
@WebServlet({ "/PurchaseServlet", "/purchase" })
public class PurchaseServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.setContentType("text/html;charset=utf-8");
		//response.getWriter().append("Served at: ").append(request.getContextPath());
        String id=request.getParameter("id");
        if(id==null) {
        	String url="/hello3/ListBookServlet";
        	response.sendRedirect(url);
        	return;
        }
        Book book=BookDB.getBook(id);
        HttpSession session=request.getSession();
        List<Book> cart=(List) session.getAttribute("cart");
        if(cart==null) {
        	cart=new ArrayList<Book>();
        	session.setAttribute("cart", cart);
        }
        cart.add(book);
        Cookie cookie=new Cookie("JSESSIONID",session.getId());
        cookie.setMaxAge(60*30);
        cookie.setPath("/hello3");
        response.addCookie(cookie);
        response.sendRedirect("/hello3/CartServlet");
        
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

创建一个名称为CartServlet的Servlet类,显示用户义卖图书列表:

package cn.com;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * Servlet implementation class CartServlet
 */
@WebServlet({ "/CartServlet", "/cart" })
public class CartServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub	
		response.setContentType("text/html;charset=utf-8");

		//response.getWriter().append("Served at: ").append(request.getContextPath());
		PrintWriter out=response.getWriter();
		List<Book> cart=null;
		HttpSession session=request.getSession(false);
		boolean cartFlag=true;
		if(session==null) {
			cartFlag=false;
		}
		else {
			cart=(List) session.getAttribute("cart");
			if(cart==null) {
				cartFlag=false;
			}
		}
		if(!cartFlag) {
			out.write("对不起，你的购物车里面没有图书，请购买！");
		
		}
		else {
			out.write("购买图书如下："+"<br/>");
			for(Book book:cart) {
				out.write("购买的图书："+book.getName()+"<br/>");
			}
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

选择一个书籍后实现效果如下：
在这里插入图片描述
3、使用session技术实现用户登录
1、创建用户封装信息类的类

2、创建indexServlet类用于显示网站的首页面，并显示登录信息，为了判断用户是否登录，该类实现时，获取了保存了用户信息的session对象

3、创建用于显示用户登陆成功的页面的loginservlet类，如果登陆成功，则跳转到网站首页，否则登陆失败
在这里插入图片描述
4、通过编写logoutservlet用于完成用户注销功能，当用户点击‘退出’时，该类将session对象的用户信息移除并返回网站首页面

5、创建一个html文件用于填写用户登录表单信息