Java Web程序设计第9章课后第2题

2. 在上题中图书信息的后面增加一个“添加到购物车”链接，单击可以将图书添加到购物车。在页面底部有一个“查看购物车”链接，可以到另一个页面中查看购物车中的内容。在购物车内容显示时，后面有一个“从购物车中删除”链接，单击，又能将该图书从购物车中删除。要求所有的动作由Servlet完成。

先完成第一题
仿照search.jsp，写个cart.jsp。注意“删除”是一个超链接，并且在链接后面还要跟上id这个参数，方便后面Servlet的删除操作（其实传递数组下标会更加方便）

购物车

<%
    ArrayList cart = (ArrayList) session.getAttribute("cart");
    if (cart != null) {
%>

    <%
            for (book b : cart) {
                out.print("");
                out.print("");
                out.print("");
                out.print("");
                out.print(String.format("", b.id));
                out.print("");
            }
        }
    %>

    

        
图书ID
        
图书名称
        
图书价格
        
操作
    
" + b.id + "
" + b.name + "
" + b.price + "
删除


返回查询页面

记得在search,jsp中加上超链接跳转到cart.jsp

查看购物车

然后再写DeleteServlet，一些细节参见注释

@WebServlet(name = "DeleteServlet", urlPatterns = {"/deleteServlet"})
public class DeleteServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理响应乱码
        response.setContentType("text/html;charset=utf-8");

        // 处理请求乱码
        request.setCharacterEncoding("utf-8");

        HttpSession session = request.getSession();
        ArrayList cart = (ArrayList) session.getAttribute("cart");
        String id = request.getParameter("id");
        if (id != null && cart != null) {
            for (book b : cart) {
                if (b.id.equals(id)) {  // 其实也可以根据下标删除，但是我这里懒得改了
                    cart.remove(b);
                    break;
                }
            }
            session.setAttribute("cart", cart);  // 要把修改后的cart存入session
            PrintWriter out = response.getWriter();
            out.print("");  // 记得跳转回cart.jsp。我在这里还加了个提示框表明删除成功
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

cart.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page import="chapter9.book" %>
<%@ page import="java.util.ArrayList" %>


    


购物车

<%
    ArrayList cart = (ArrayList) session.getAttribute("cart");
    if (cart != null) {
%>

    <%
            for (book b : cart) {
                out.print("");
                out.print("");
                out.print("");
                out.print("");
                out.print(String.format("", b.id));
                out.print("");
            }
        }
    %>

    

        
图书ID
        
图书名称
        
图书价格
        
操作
    
" + b.id + "
" + b.name + "
" + b.price + "
删除


返回查询页面

DeleteServlet.java

package chapter9.servlet;

import chapter9.book;

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;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
import java.util.ArrayList;

@WebServlet(name = "DeleteServlet", urlPatterns = {"/deleteServlet"})
public class DeleteServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 处理响应乱码
        response.setContentType("text/html;charset=utf-8");

        // 处理请求乱码
        request.setCharacterEncoding("utf-8");

        HttpSession session = request.getSession();
        ArrayList cart = (ArrayList) session.getAttribute("cart");
        String id = request.getParameter("id");
        if (id != null && cart != null) {
            for (book b : cart) {
                if (b.id.equals(id)) {
                    cart.remove(b);
                    break;
                }
            }
            session.setAttribute("cart", cart);
            PrintWriter out = response.getWriter();
            out.print("");
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}