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。
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;
@WebServlet("/LastAccessServlet")
public class LastAccessServlet 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");
cookie[] cookies=request.getcookies();
String lastTime=null;
for(int i=0;cookies!=null&&i
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。
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
package bai.session.example01;
import java.util.Collection;
import java.util.linkedHashMap;
import java.util.Map;
public class BookDB {
private static Map map = new linkedHashMap();
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 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。
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;
@WebServlet("/ListBookServlet")
public class ListBookServlet 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");
//1,
Collection books= BookDB.getAll();
PrintWriter out=response.getWriter();
out.print("本网站售卖的书籍："+"
");
for(Book b:books) {
String name= b.getName();
String id=b.getId();
String url="点击购买";
out.print("图书名称： "+name+" "+url+"
");
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
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。
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;
@WebServlet("/ListBookServlet")
public class ListBookServlet 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");
//1,
Collection books= BookDB.getAll();
PrintWriter out=response.getWriter();
out.print("本网站售卖的书籍："+"
");
for(Book b:books) {
String name= b.getName();
String id=b.getId();
String url="点击购买";
out.print("图书名称： "+name+" "+url+"
");
}
}
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
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 list=(List)session.getAttribute("cart");//获得购物车
if(list==null) {//首次购买
list =new ArrayList();
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
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 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.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："+"
");
for(Book b:cart) {
out.print(b.getName()+"
");
}
}
}
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
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
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，请登录");
}else {
response.getWriter().print("你已登录，欢迎你，"+user.getUsername()+"!");
response.getWriter().print("退出");
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
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。
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
Insert title here
最后登录就行。
