有关商品业务的增加、删除、修改、全查。

通过数据库后端把数据响应到jsp前端 java代码通过JDBC连接数据库、做出增加、删除、修改、全查操作。

一、数据库内容

二.全查操作

三、添加操作

四、删除操作

五、修改操作

一、数据库内容

#判断存在即删除数据库
drop database if exists mydb;
#创建数据库
create database mydb;
#使用数据库
use mydb;#创建表
create table t_user
(uid int primary key auto_increment,username varchar(20),password varchar(20),phone varchar(11),address varchar(50)
);insert into t_user(username,password,phone,address) values('张三','666','18965423548','南阳');
insert into t_user(username,password,phone,address) values('李四','333','18754263548','许昌');
insert into t_user(username,password,phone,address) values('小美','123','18565234759','信阳');select * from t_user where username=? and password=?
select * from t_user;create table t_goods
(gid int primary key auto_increment,gname varchar(20),price double,mark varchar(100)
);insert into t_goods(gname,price,mark) values('泡面',4.5,'够香够辣就是这个味！');
insert into t_goods(gname,price,mark) values('火腿',8.5,'肉质细腻Q弹！');
insert into t_goods(gname,price,mark) values('雪碧',3.5,'清爽冰凉随心爽！');select * from t_goods;

1.用户信息

2.商品信息

二.全查操作

1.创建一个关于商品的jsp文件（goods.jsp）

goods.jsp：


<%@ page contentType="text/html;charset=UTF-8" language="java" %><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head><title>登陆成功</title>
</head>
<body style="background-color: lightblue;margin: 200px auto;
background-image:url(img/3.jpg);background-size: 100% 100%">
<h1>登录成功</h1>
<h2>欢迎来自${user.address}的${user.username}访问主页</h2>
<table><thead><!--<a href="addGoods.jsp">添加商品</a>--><tr><th>商品编号</th><th>商品名称</th><th>商品价格</th><th>商品说明</th></tr></thead><tboby id="List"><c:forEach items="${goodsList}" var="goods"><tr><td> ${goods.gid}</td><td> ${goods.gname}</td><td> ${goods.price}</td><td> ${goods.mark}</td><td><a href="#">修改</a><a href="dell?gid=${goods.gid}">删除</a></td></tr></c:forEach></tboby>
</table></body>
</html>

2.创建一个selectAll方法

ublic List<Goods> selectAll() {List<Goods> goodsList = new ArrayList<>();try {Class.forName(jdbcdirver);con = DriverManager.getConnection(jdbcurl, jdbcuser, jdbcpassword);String sql = "select * from t_goods";pstm = con.prepareStatement(sql);rs = pstm.executeQuery();while (rs.next()) {//从结果集中获取数据，封装到Goods对象中Goods goods = new Goods();goods.setGid(rs.getInt("gid"));goods.setGname(rs.getString("gname"));goods.setPrice(rs.getDouble("price"));goods.setMark(rs.getString("mark"));//把当前行对应的对象存储到集合中goodsList.add(goods);}} catch (Exception e) {e.printStackTrace();} finally {try {if (rs != null) {rs.close();}if (pstm != null) {pstm.close();}if (con != null) {con.close();}} catch (SQLException e) {e.printStackTrace();}}return goodsList;}

3.创建一个Servlet类（servletAllGoods类）

package com.nai.servlet;import com.nai.Dao.impl.GoodsDaoImpl;
import com.nai.bean.Goods;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;@WebServlet("/selectAllGoods")
public class servletAllGoods extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request,response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//查询所有商品的信息GoodsDaoImpl goodsDao=new GoodsDaoImpl();List<Goods> goodsList=goodsDao.selectAll();System.out.println(goodsList);//把数据传递到前端页面//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();//向session中存入商品信息集合session.setAttribute("goodsList",goodsList);//登录成功，跳转到上面response.sendRedirect("goods.jsp");}
}

三、添加操作

步骤图：

首先创建一个主页文件加入添加代码（超链接）


<%@ page contentType="text/html;charset=UTF-8" language="java" %><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head><title>登陆成功</title>
</head>
<body style="background-color: lightblue;margin: 200px auto;
background-image:url(img/3.jpg);background-size: 100% 100%">
<h1>登录成功</h1>
<h2>欢迎来自${user.address}的${user.username}访问主页</h2>
<table><thead><a href="addGoods.jsp">添加商品</a><tr><th>商品编号</th><th>商品名称</th><th>商品价格</th><th>商品说明</th></tr></thead><tboby id="List"><c:forEach items="${goodsList}" var="goods"><tr><td> ${goods.gid}</td><td> ${goods.gname}</td><td> ${goods.price}</td><td> ${goods.mark}</td><td><a href="#">修改</a><a href="dell?gid=${goods.gid}">删除</a></td></tr></c:forEach></tboby>
</table></body>
</html>

其次创建一个有关商品添加的jsp文件

<%--Created by IntelliJ IDEA.User: 奈申博Date: 2023/2/24Time: 14:04To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>Title</title>
</head>
<body>
<form action="addGood" method="post">
商品名称:<input  type="text" name="gname" value="" placeholder="商品名称"><br>
商品价格:<input  type="number" step="0.01" name="price" value="" placeholder="商品价格"><br>
商品说明:<input type="text" name="mark" value="" placeholder="商品说明"><br>
<input type="submit" value="添加" >
</form>
</body>
</html>

创建一个添加（add）方法

public int add(Goods goods) {System.out.println("执行add");try {Class.forName(jdbcdirver);con = DriverManager.getConnection(jdbcurl, jdbcuser, jdbcpassword);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();} catch (Exception e) {e.printStackTrace();} finally {try {if (pstm != null) {pstm.close();}if (con != null) {con.close();}} catch (Exception e) {e.printStackTrace();}}return row;}

最后创建Java代码 Servlet类（AddGoods类）

package com.nai.servlet;import com.nai.Dao.impl.GoodsDaoImpl;
import com.nai.bean.Goods;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet("/addGood")
public class AddGoods extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request,response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {System.out.println("执行AddGoods");request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");//获取请求参数并封装到Goods对象中Goods goods= new Goods();goods.setGname(request.getParameter("gname"));//数据转换goods.setPrice(Double.parseDouble(request.getParameter("price")));// request.getParameter("price");goods.setMark(request.getParameter("mark"));//执行JDBC的添加操作GoodsDaoImpl  goodsDao= new GoodsDaoImpl();int row=goodsDao.add(goods);if(row>0){//添加成功请求selectAllGoods地址 执行对应的select（查询商品信息 存入session中 跳转到主页）request.getRequestDispatcher("selectAllGoods").forward(request,response);}else {request.setAttribute("user_msg","添加商品出错了！");request.getRequestDispatcher("user.jsp").forward(request,response);}}
}

添加展示图：

四、删除操作

步骤图：

在主页文件中加入删除商品的代码（超链接）


<%@ page contentType="text/html;charset=UTF-8" language="java" %><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head><title>登陆成功</title>
</head>
<body style="background-color: lightblue;margin: 200px auto;
background-image:url(img/3.jpg);background-size: 100% 100%">
<h1>登录成功</h1>
<h2>欢迎来自${user.address}的${user.username}访问主页</h2>
<table><thead><a href="addGoods.jsp">添加商品</a><tr><th>商品编号</th><th>商品名称</th><th>商品价格</th><th>商品说明</th></tr></thead><tboby id="List"><c:forEach items="${goodsList}" var="goods"><tr><td> ${goods.gid}</td><td> ${goods.gname}</td><td> ${goods.price}</td><td> ${goods.mark}</td><td><a href="#">修改</a><a href="dell?gid=${goods.gid}">删除</a></td></tr></c:forEach></tboby>
</table></body>
</html>

创建一个删除（delect）方法

public int delect(int gid)  {System.out.println("执行DE");try {Class.forName(jdbcdirver);con = DriverManager.getConnection(jdbcurl, jdbcuser, jdbcpassword);String sql = "delete from t_goods where gid=?";pstm = con.prepareStatement(sql);pstm.setObject(1,gid);row = pstm.executeUpdate();} catch (Exception e) {e.printStackTrace();} finally {try {if (pstm != null) {pstm.close();}if (con != null) {con.close();}} catch (Exception e) {e.printStackTrace();}}return row;}

再创建一个Servlet类（DellGoods类）

package com.nai.servlet;import com.nai.Dao.impl.GoodsDaoImpl;
import com.nai.until.JDBCUtil;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.sql.Connection;@WebServlet("/dell")
public class DellGoods extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request, response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//        解决中文乱码问题request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");int id =Integer.parseInt(request.getParameter("gid"));Connection con = null;int user =0;GoodsDaoImpl goodsDao = new GoodsDaoImpl();user=goodsDao.delect(id);if (user>0){request.getRequestDispatcher("selectAllGoods").forward(request,response);}else {response.sendRedirect("user.jsp");}}}

删除展示图：（删除可乐）

五、修改操作

创建一个Servlet类（FindGoodsById类）通过gid查询商品信息

package com.nai.servlet;import com.nai.Dao.impl.GoodsDaoImpl;
import com.nai.bean.Goods;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet("/findById")
public class FindGoodsById extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request,response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {int gid=Integer.parseInt(request.getParameter("gid"));//根据gid查询商品信息GoodsDaoImpl goodsDao= new GoodsDaoImpl();Goods goods=goodsDao.selectById(gid);if(goods!=null){//把数据存储到request域对象中 然后请求转发到页面request.setAttribute("goods",goods);request.getRequestDispatcher("showGoods.jsp").forward(request,response);}else{//登录失败  跳转到错误页面request.setAttribute("user_msg","修改出现异常");request.getRequestDispatcher("user.jsp").forward(request,response);}}
}

再创建一个修改方法（UpdateGoods类）

public int UpdateGoods(Goods goods){int row=0;try{Class.forName(jdbcdirver);con=  DriverManager.getConnection(jdbcurl,jdbcuser,jdbcpassword);String sql="update t_goods set gname=?,price=?,mark=? where  gid=?";pstm=   con.prepareStatement(sql);pstm.setObject(1,goods.getGname());pstm.setObject(2,goods.getPrice());pstm.setObject(3,goods.getMark());pstm.setObject(4,goods.getGid());row= pstm.executeUpdate();}catch (Exception e){e.printStackTrace();}finally {try {if (pstm != null) {pstm.close();}if (con != null) {con.close();}} catch (Exception e) {e.printStackTrace();}}return row;}

和一个jsp文件有关商品修改主页

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>商品信息管理员</title>
</head>
<body>
<form action="updateGoods" method="post">商品编号:<input  type="text" name="gid" value="${goods.gid}" placeholder="商品编号" readonly="readonly"><br>商品名称:<input type="text" name="gname" value="${goods.gname}" placeholder="商品名称"><br>商品价格:<input  type="number" step="0.01" name="price" value="${goods.price}" placeholder="商品价格"><br>商品说明:<input type="text" name="mark" value="${goods.mark}" placeholder="商品说明"><br>
<input type="submit" value="修改" >
</form>
</body>
</html>

最后跳转到后端java代码 servlet类中的UpdateGoods类中、引用修改方法

package com.nai.servlet;import com.nai.Dao.impl.GoodsDaoImpl;
import com.nai.bean.Goods;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet("/updateGoods")
public class UpdateGoods extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request,response);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("utf-8");response.setCharacterEncoding("utf-8");//获取表单请求的数据 封装到goods对象中Goods goods=new Goods();goods.setGid(Integer.parseInt(request.getParameter("gid")));goods.setGname(request.getParameter("gname"));goods.setPrice(Double.parseDouble(request.getParameter("price")));goods.setMark(request.getParameter("mark"));//执行JDBCGoodsDaoImpl goodsDao =new GoodsDaoImpl();int row =goodsDao.UpdateGoods(goods);if (row>0){request.getRequestDispatcher("selectAllGoods").forward(request,response);}else {request.setAttribute("user_msg","修改商品出错了！");request.getRequestDispatcher("user.jsp").forward(request,response);}}}

修改展示：