JavaWeb-05 会话及其会话技术

实例：显示用户上次访问时间

###1.创建Servlet
在Eclipse中新建Web项目chapter05,并在该项目下新建一个名称为pidan.cookie.example的包，在该包中编写一个名称为LastAccessServlet的Servlet类，用于实现获取 Cookie信息并将当前时间作为Cookie 值发送给客户端。

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package bai.cookie.example;
 
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")
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 {
		response.setContentType("text/html;charset=utf-8");
		
		Cookie[] cookies=request.getCookies();
		
		String lastTime=null;
		for(int i=0;cookies!=null&&i<cookies.length;i++) {
			String name=cookies[i].getName();
			if("lastccess".equals(name)) {
				lastTime=cookies[i].getValue();
			}
		}
		if(lastTime==null) {
			response.getWriter().print("第一次访问本网站！");
		}else {
			response.getWriter().print("上次访问的时间是："+lastTime);
			response.getWriter().print("学号：2020080604029");
		}
		String time=String.format("%tF%<tT", new Date());
		Cookie cookie=new Cookie("lastccess", time);
		Cookie cookie1 = new Cookie("dashuju", "2004");
		response.addCookie(cookie);
		response.addCookie(cookie1);
	}
 
	/**
	 * @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);
	}
 
}

由于这里直接通过 @WebServlet 标签配置URL映射,不再需要从 web.xml 里面配置 servlet。

启动Tomcat 服务器，在浏览器的地址栏中输入 localhost:8080/chapter05/LastAccessServlet”访问 LastAccessServlet,由于是第一次访问LastAccessServlet：

重新访问地址（刷新页面）：

实例：实现购物车

1.新建一个名称为pidan.session.example01的包,在该包中创建一个名称为Book的类，该类用于封装图书的信息，
其中定义了id和name属性，分别用来表示书的编号和名称。

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package bai.session.example01;
 
public class Book {
	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;
	}
}

###2.在pidan.session.example01包中创建一个名称为BookDB的类，该类用于模拟保存所有图书的数据库。

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package bai.session.example01;
 
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);
	}
}

###3.创建一个名称为ListBookServlet的Servlet类，
该Servlet用于显示所有可购买图书的列表，通过单击“购买”链接，便可将指定的图书添加到购物车中。

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package bai.session.example01;
 
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 BookDB
 */
@WebServlet("/ListBookServlet")
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 {
		response.setContentType("text/html;charset=utf-8");
		//1,
		Collection <Book> books= BookDB.getAll();
		
		PrintWriter out=response.getWriter();
		
		out.print("本网站售卖的书籍："+"<br/><br/>");
		
		for(Book b:books) {
			String name= b.getName();
			String id=b.getId();
			String url="<a href='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);
	}
 
}

###4.创建一个名称为PurchaseServlet的Servlet类

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package bai.session.example01;
 
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;
 
@WebServlet("/purcharse")
public class purcharseServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
 
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		String id=request.getParameter("id");
		System.out.println("id :"+id);		
		if(id==null) {
			response.sendRedirect("list");
			return;
		}
		Book book=BookDB.getBook(id);
		HttpSession session=request.getSession();//获得内存区域
		List<Book> list=(List<Book>)session.getAttribute("cart");//获得购物车
		if(list==null) {//首次购买
			list =new ArrayList<Book>();	
			session.setAttribute("cart", list);
		}
		list.add(book);
		Cookie cookie =new Cookie("JESSIONID", session.getId());
		response.addCookie(cookie);
		response.sendRedirect("cart");
	}
 
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
 
}

###5.创建一个名称为CartServlet的Servlet类，该类主要用于展示用户已经购买的图书列表

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package bai.session.example01;
 
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;
 
 
 
@WebServlet("/cart")
public class CartServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
 
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		PrintWriter out=response.getWriter();
		List<Book> cart=null;
		HttpSession session = request.getSession(false);
		boolean cartFlag=true;
		if(session==null) {
			cartFlag=false;
		}else {
			cart=(List<Book>)session.getAttribute("cart");
			if(cart==null) {
				cartFlag=false;
			}
		}
		if(!cartFlag) {
			out.print("您的购物车里面没有图书，请前往购买");
		}else {
			out.print("购买图书如下："+"<br/>");
			for(Book b:cart) {
				out.print(/*"购买的图书："+*/b.getName()+"<br/>");
			}
		}
	}
 
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
 
}

###6.启动Tomcat 服务器，访问ListBookServlet,
1.单击图中“javaweb开发”后的“点击购买”链接
2.再次访问（或点击浏览器的返回上一页）ListBookServlet，选择“jdbc开发”后的“点击购买”链接

任务：实现用户登录

实现效果：

用户登录的整个流程，当用户访问某个网站的首界面时，首先会判断用户是否登录，如果已经登录则在首界面中显示用户登录信息，否则进入登录页面，完成用户登录功能，然后显示用户登录信息。
在用户登录的情况下，如果单击用户登录界面中的“退出”时，就会注销当前用户的信息，返回首界面。

###1.创建封装用户信息类
1.在chapter05项目的src下新建一个名称为pidan.session.example02的包,在包中编写一个名称为User的类，
User类中包含username和password两个属性以及其getter和setter方法

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package bai.session.example02;
 
public class User {
	private String username;
	private String password;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
}

2.创建Servlet
在pidan.session.example02包中编写IndexServlet 类， 该Servlet 用于显示网站的首界面

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package bai.session.example02;
 
import java.io.IOException;
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;
 
@WebServlet("/IndexServlevt")
public class IndexServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		HttpSession session= request.getSession();
		User user =(User) session.getAttribute("user");
		if(user==null) {
			response.getWriter().print("您还没登录，请<a href='login.html'>登录</a>");
		}else {
			response.getWriter().print("你已登录，欢迎你，"+user.getUsername()+"!");
			response.getWriter().print("<a href='LogoutServlet'>退出</a>");
			Cookie cookie =new Cookie("JSESSIONID", session.getId());
			cookie.setMaxAge(60*30);
			cookie.setPath("/chapter05");
			response.addCookie(cookie);
		}
	}
 
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
 
}**

3.在pidan.session.example02包中编写LoginServlet,该Servlet用于显
示用户登录成功后的界面

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package bai.session.example02;
 
import java.io.IOException;
import java.io.PrintWriter;
 
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setContentType("text/html;charset=utf-8");
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		PrintWriter pw=response.getWriter();
		if(("pidan").equals(username)&&("666").equals(password)) {
			User user = new User();
			user.setUsername(username);
			user.setPassword(password);
			request.getSession().setAttribute("user", user);
			response.sendRedirect("IndexServlevt");
		}else {
			pw.write("用户名或密码错误，登录失败");
		}
	}
 
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
 
}

4.在pidan.session.example02包中编写LogoutServet,该Servlet用于完
成用户注销功能，当用户单击【退出】时，该类会将Session对象中的用户信息移除，并跳
转到网站的首界面。

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package bai.session.example02;
 
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
@WebServlet("/LogoutServlet")
public class LogoutServlet extends HttpServlet {
 
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.getSession().removeAttribute("user");
		response.sendRedirect("IndexServlevt");
	}
 
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}
 
}

3.创建登陆页面

在chapter05项目的WebContent目录下创建一个名称为login.html的页面，该页面中包含用户登录表单信息

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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form name="reg" action="/chapter05/LoginServlet" method="post">
		用户名：<input name="username" type="text" /><br/>
		密__码：<input name="password" type="password" /><br/>
		<input type="submit" value="提交" id="bt" />
	</form>
</body>
</html>

最后登录就行了