更新在njaccp的編程技巧板塊
 
Session簡單實現(xiàn)購物功能
 
1,IndexServlet.java 主頁Servlet實現(xiàn)主頁顯示商品
 
 
    import java.io.IOException; 
    import java.io.PrintWriter; 
    import java.util.LinkedHashMap; 
    import java.util.Map; 
    import java.util.Set; 
    import javax.servlet.ServletException; 
    import javax.servlet.http.HttpServlet; 
    import javax.servlet.http.HttpServletRequest; 
    import javax.servlet.http.HttpServletResponse; 
     
    //首頁：列出所有書 
    public class IndexServlet extends HttpServlet { 
     
        public void doGet(HttpServletRequest request, HttpServletResponse response) 
                throws ServletException, IOException { 
            response.setContentType("text/html;charset=UTF-8"); 
            PrintWriter out = response.getWriter();  
            request.getSession();    
            out.write("本網(wǎng)站有如下書：<br/>");    
            Set<Map.Entry<String,Book>> set = DB.getAll().entrySet(); 
            for(Map.Entry<String,Book> me : set){ 
                Book book = me.getValue(); 
                String url = "/day07/servlet/BuyServlet?id=" + book.getId(); 
                url = response.encodeURL(url); 
                out.println(book.getName()  + "   <a href='"+url+"'>購買</a><br/>"); 
            }    
        } 
     
        public void doPost(HttpServletRequest request, HttpServletResponse response) 
                throws ServletException, IOException { 
            doGet(request, response); 
        } 
     
    } 
 
2,BuyServlet.java 該Servlet實現(xiàn)購買頁面
 
 
    import java.io.IOException; 
    import java.util.ArrayList; 
    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 BuyServlet extends HttpServlet { 
        public void doGet(HttpServletRequest request, HttpServletResponse response) 
                throws ServletException, IOException { 
            String id = request.getParameter("id"); 
            Book book = (Book) DB.getAll().get(id);  //得到用戶想買的書  
            HttpSession session = request.getSession(); 
            /*Cookie cookie = new Cookie("JSESSIONID",session.getId());
            cookie.setMaxAge(30*60);
            cookie.setPath("/day07");
            response.addCookie(cookie);*/    
            List list = (List) session.getAttribute("list");  //得到用戶用于保存所有書的容器 
            if(list==null){ 
                list = new ArrayList(); 
                session.setAttribute("list", list); 
            } 
            list.add(book); 
            //request.getRequestDispatcher("/servlet/ListCartServlet").forward(request, response);   
            String url = response.encodeRedirectURL("/day07/servlet/ListCartServlet");//重新URL 
            //System.out.println(url); 
            response.sendRedirect(url);  
        } 
        public void doPost(HttpServletRequest request, HttpServletResponse response) 
                throws ServletException, IOException { 
            doGet(request, response); 
        } 
     
    } 
 
3，ListCartServlet.java 實現(xiàn)將購買的商品通過Session保存發(fā)給ListCartServlet,顯示你購買的商品
 
 
    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 ListCartServlet extends HttpServlet { 
     
        public void doGet(HttpServletRequest request, HttpServletResponse response) 
                throws ServletException, IOException { 
            response.setContentType("text/html;charset=UTF-8"); 
            PrintWriter out = response.getWriter();  
            HttpSession session = request.getSession(); 
            List<Book> list = (List) session.getAttribute("list"); 
            if(list==null || list.size()==0){ 
                out.write("對不起，您還沒有購買任何商品!!"); 
                return; 
            }    
            //顯示用戶買過的商品 
            out.write("您買過如下商品:<br>"); 
            for(Book book : list){ 
                out.write(book.getName() + "<br/>"); 
            }        
        } 
        public void doPost(HttpServletRequest request, HttpServletResponse response) 
                throws ServletException, IOException { 
     
            doGet(request, response); 
        } 
      
    }