Session 简单购物车
package session.test;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
//代表网站，列出所有书籍
public class SessionDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html);charset=UTF-8");
PrintWriter out = response.getWriter();
//输出网站商品
out.write("本网站有如下书籍:<br/>");
Map<String,Book> map = Db.getAll();
for(Map.Entry<String,Book>entry:map.entrySet()) {
Book book = entry.getValue();
out.println("<a href='/session/servlet/SessionDemo2?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a><br/>");
}
//2,显示用户看过的商品
out.print("<br/>您曾经浏览过的商品：<br/>");
HttpSession session= request.getSession(false);
if(session==null) {
out.write("尚未购买商品<br/>");
return;
}
out.write("购物车中商品:<br/>");
List<String> list = (List)session.getAttribute("list");
for(String str:list) {
out.write(str+"<br/>");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
class Db{
//private Map map = new HashMap();
private static Map<String,Book> map = new LinkedHashMap<String,Book>();
static {
map.put("1",new Book("1","水浒传","施耐庵","名著"));
map.put("2",new Book("2","三国演义","罗贯中","名著"));
map.put("3",new Book("3","西游记","吴承恩","名著"));
map.put("4",new Book("4","红楼梦","曹雪芹","名著"));
map.put("5",new Book("5","金-瓶梅","笑笑生","名著"));
}
public static Map<String, Book> getAll() {
return map;
}
}
class Book{
private String id;
private String name;
private String author;
private String description;
public Book() {
super();
// TODO Auto-generated constructor stub
}
public Book(String id, String name, String author, String description) {
super();
this.id = id;
this.name = name;
this.author = author;
this.description = description;
}
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;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
package session.test;
import java.util.List;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import javax.servlet.ServletException;
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;
//购买servlet
public class SessionDemo2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html);charset=UTF-8");
PrintWriter out = response.getWriter();
//根据用户带过来的id，显示相应商品的详细信息
String id = request.getParameter("id");
Book book = (Book)Db.getAll().get(id);
out.write(book.getId() + "<br/>");
out.write(book.getName() + "<br/>");
out.print(book.getAuthor() + "<br/>");/////////////////////////////
out.write(book.getDescription() + "<br/>");
//构建session
HttpSession session = request.getSession();
//用集合来保存买的东西。
List list = (List) session.getAttribute("list");
if(list==null) {
list = new ArrayList();
session.setAttribute("list", list);
}
list.add(book);
//session.setAttribute("list", list);
// request.getRequestDispatcher("/servlet/SessionDemo1").forward(request, response);
// this.getServletContext().getRequestDispatcher("/servlet/SessionDemo1").forward(request, response);
response.sendRedirect(request.getContextPath()+"/servlet/SessionDemo3");//
}
private String buildSession(String id, HttpServletRequest request) {
//bookHistory = null
String bookHistory = null;
Cookie cookies[] = request.getCookies();
for(int i=0;cookies!=null&&i<cookies.length;i++) {
if(cookies[i].getName().equals("bookHistory"));
bookHistory = cookies[i].getValue();
}
if(bookHistory==null) {
return id;
}
LinkedList<String> list = new LinkedList<String>(Arrays.asList(bookHistory.split("\\,")));
if(list.contains(id)) {
list.remove(id);
}else {
if(list.size()>=3) {
list.removeLast();
}
}
list.addFirst(id);
StringBuffer sb = new StringBuffer();
for(String bid : list) {
sb.append(bid + ",");
}
return sb.deleteCharAt(sb.length()-1).toString();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
package session.test;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class SessionDemo3 extends HttpServlet {
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
out.write("<br/>");
out.write("<br/>");
//2,显示用户看过的商品
out.print("<br/>您曾经浏览过的商品：<br/>");
HttpSession session= request.getSession(false);
if(session==null) {
out.write("尚未购买商品<br/>");
return;
}
out.write("购物车中商品:<br/>");
List list = (List)session.getAttribute("list");
for(Object str:list) {
Book book = (Book)str;
out.write(book.getName()+"<br/>");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
}
}
客户端无法存cookie的情况，把sessionID存到地址栏。
request.getSession();//先创建session不然下面这句不会有效果
……
String url = response.encodeRedirectUrl(url);
对于重定向的url：
String url = response.encodeRedirectURL(……);
session Id存在地址栏，如果客户端支持cookie会自动存在cookie里，否则才会存在地址栏
