Java (adding and deleting pages)

ideas to add

Requirement:
Add a record from the jsp page to the database and display it on the interface

Analysis:
1. Create a jsp page
2. Create a Servlet>addGoods method
1. Set the request encoding
2. Get the values of all parameters
3. Encapsulate the object 4.
Call the addGoods method
3. Create a Service interface>addGoods method
1. Call addGoods(Goods) Method
4. Create GoodsDao interface>addGoods method
1. Create sql statement
2. Get the result set

Code

jsp page

<%@ page import="java.util.List" %>
<%@ page import="com.wang.bean.Goods" %>
<%@ page import="com.wang.bean.User" %><%--
  Created by IntelliJ IDEA.
  User: 小m
  Date: 2023/2/16
  Time: 12:21
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!--在页面导入jstl的核心类库--->
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>主页</title>
</head>
<body>
       <h2>欢迎来自${user.address}的${user.username}来到主页！</h2>
       <a href="addGoods.jsp"></a>
    <table>
        <tr>
            <th>商品编号</th>
            <th>商品名称</th>
            <th>商品价格</th>
            <th>商品介绍</th>
        </tr>

        <!--items:要遍历的集合元素   var：临时变量-->
       <c:forEach items="${goodsList}" var="goods">
                <tr>
                    <td>${goods.gid}</td>
                    <td>${goods.gname}</td>
                    <td>${goods.price}</td>
                    <td>${goods.mark}</td>
                    <td>
                        <a href=""></a>
                    </td>
                </tr>
       </c:forEach>

    </table>
</body>
</html>

SelectAllGoods

package com.wang.servlet;

import com.wang.bean.Goods;
import com.wang.dao.GoodsDao;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;

@WebServlet("/selectAllGoods")
public class SelectAllGoods extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("SelectAllGoods-doGet...");
        doPost(request,response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1.执行查询业务
        // 2.查询所有商品信息
        GoodsDao goodsDao = new GoodsDao();
        List<Goods> goodsList = goodsDao.selectAllGoods();
        System.out.println(goodsList);
        // 3.把数据传递到前端页面
        // 3.1通过request获取session对象，该对象可以向前端传输数据的容器
        HttpSession session = request.getSession();
        // 4.向session中存入商品信息集合
        session.setAttribute("goodsList",goodsList);
        String id = session.getId();
        System.out.println("sessionID:"+id);

        // 4.登录成功,跳转到登录页
        response.sendRedirect("zhuye.jsp");

    }
}

addGoods

 public int addgoods(Goods goods) {
        try {
                con=JDBCUtil.getCon();
                String sql="insert into t_goods(gname,price,mark) values (?,?,?)";
                //
            pstm = con.prepareStatement(sql);
            pstm.setObject(1,goods.getGname());
            pstm.setObject(2,goods.getPrice());
            pstm.setObject(3,goods.getMark());
            //
            row=pstm.executeUpdate();
            System.out.println(row);

        } catch (Exception e) {
                e.printStackTrace();
        } finally {
            //释放资源
            JDBCUtil.close(con, pstm);
        }
        return row;
    }

Delete ideas

Idea:

First, use javaScript to obtain the name of the selected record in the check box, store each selected record name in a variable, and then transfer it to the background for batch deletion.

  <!--items:要遍历的集合元素   var：临时变量-->
       <c:forEach items="${goodsList}" var="goods">
                <tr>
                    <td>${goods.gid}</td>
                    <td>${goods.gname}</td>
                    <td>${goods.price}</td>
                    <td>${goods.mark}</td>
                    <td>
                        <a href="#">修改</a>
                        <a href="del?gid=${goods.gid}">删除</a>
                    </td>
                </tr>
       </c:forEach>

Here we mainly use tags in jsp to display data.

Then look at the code in the servlet

@Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
 
        Goods goods=new Goods();
        goods.setGname(request.getParameter("gname"));
        goods.setPrice(Double.parseDouble(request.getParameter("price")));
        goods.setMark(request.getParameter("mark"));
 
        GoodsDao goodsDao=new GoodsDao();
        int row=goodsDao.add(goods);
 
        if (row>0){
            request.getRequestDispatcher("ServletAllGoods").forward(request,response);
        }else {
            request.setAttribute("error_msg","添加信息失败");
            request.getRequestDispatcher("error_jsp").forward(request,response);
        }
    }
}

Through the configuration of the Servlet, obtain the path to connect the Servlet and Tianjia to facilitate processing of browser requests.

public int add(Goods goods) {
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, psw);
            String sql = "insert into t_goods(gname,price,mark)values(?,?,?)";
            psmt = connection.prepareStatement(sql);
            psmt.setObject(1, goods.getGname());
            psmt.setObject(2, goods.getPrice());
            psmt.setObject(3, goods.getMark());
            row=psmt.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //8.关闭资源
            try {
 
                if (psmt != null) {
                    psmt.close();
                }
                if (connection != null) {
                    connection.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return row;
    }
}

According to the obtained data, use string segmentation to get the name of each item that needs to be deleted, and finally call the delete method in a loop to delete!