第一步 我们先MySQL创建数据库，写数据

这两个是写数据库的软件。

 启动MySQL对应的版本型号。

user表

1.判断存在（有没有login的数据库，有就删掉）即删除。

DROP DATABASE IF EXISTS login;

2.创建数据库，使用数据库

 #创建数据库

CREATE DATABASE login;

#使用数据库

use login;

3.创建一个表我们这定义叫user，给表增添3条数据

#创建表

CREATE TABLE user(

    uid int PRIMARY KEY AUTO_INCREMENT,

    uname VARCHAR(32),

    password VARCHAR(32),

    phone VARCHAR(11),

    address VARCHAR(64)

);

INSERT INTO user(uname,password,phone,address) VALUES('张三','666','18965423548','南阳');

INSERT INTO user(uname,password,phone,address) VALUES('李四','333','18754263548','许昌');

INSERT INTO user(uname,password,phone,address) VALUES('小美','123','18565234759','信阳');

 

 4.查询表

SELECT * FROM user;

goods表

1.创建另一个表叫goods，给表增添3条数据

create table goods(

    gid int PRIMARY KEY AUTO_INCREMENT,

    gname VARCHAR(32),

    price DOUBLE,

    mark VARCHAR(128)

);

INSERT INTO goods(gname,price,mark) VALUES('泡面',4.5,'够香够辣就是这个味！');

INSERT INTO goods(gname,price,mark) VALUES('火腿',8.5,'肉质细腻Q弹！');

INSERT INTO goods(gname,price,mark) VALUES('雪碧',3.5,'清爽冰凉随心爽！');

  2.查询表

select * from goods;

整体代码如下： 

#判断存在即删除
DROP DATABASE IF EXISTS login;
#创建数据库
CREATE DATABASE login;
#使用数据库
use login;
#创建表
CREATE TABLE user(
	uid int PRIMARY KEY AUTO_INCREMENT,
	uname VARCHAR(32),
	password VARCHAR(32),
	phone VARCHAR(11),
	address VARCHAR(64)
);
INSERT INTO user(uname,password,phone,address) VALUES('张三','666','18965423548','南阳');
INSERT INTO user(uname,password,phone,address) VALUES('李四','333','18754263548','许昌');
INSERT INTO user(uname,password,phone,address) VALUES('小美','123','18565234759','信阳');
SELECT * FROM user WHERE uname = ? AND password = ?;
SELECT * FROM user;
create table goods(
	gid int PRIMARY KEY AUTO_INCREMENT,
	gname VARCHAR(32),
	price DOUBLE,
	mark VARCHAR(128)
);
INSERT INTO goods(gname,price,mark) VALUES('泡面',4.5,'够香够辣就是这个味！');
INSERT INTO goods(gname,price,mark) VALUES('火腿',8.5,'肉质细腻Q弹！');
INSERT INTO goods(gname,price,mark) VALUES('雪碧',3.5,'清爽冰凉随心爽！');
select * from goods;

 效果如下：

第二步 在IDEA中写出这两个表对应的Java实体类 

MySQL的表名要跟Java类(首字母大写)的表名一样 

User类

package com.chen.bean;
public class User {
    private Integer id;
    private String uname;
    private String password;
    private String phone;
    private String address;
    public User() {
    }
    public User(Integer id, String uname, String password, String phone, String address) {
        this.id = id;
        this.uname = uname;
        this.password = password;
        this.phone = phone;
        this.address = address;
    }
    public Integer getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUname() {
        return uname;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", uname='" + uname + '\'' +
                ", password='" + password + '\'' +
                ", phone='" + phone + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

Goods类

package com.chen.bean;
class Goods {
    private Integer gid;
    private String gname;
    private Double price;
    private String mark;
    public Goods(Integer gid, String gname, Double price, String mark) {
        this.gid = gid;
        this.gname = gname;
        this.price = price;
        this.mark = mark;
    }
    public Goods() {
    }
    @Override
    public String toString() {
        return "zhuye{" +
                "gid=" + gid +
                ", gname='" + gname + '\'' +
                ", price=" + price +
                ", mark='" + mark + '\'' +
                '}';
    }
    public Integer getGid() {
        return gid;
    }
    public void setGid(Integer gid) {
        this.gid = gid;
    }
    public String getGname() {
        return gname;
    }
    public void setGname(String gname) {
        this.gname = gname;
    }
    public Double getPrice() {
        return price;
    }
    public void setPrice(Double price) {
        this.price = price;
    }
    public String getMark() {
        return mark;
    }
    public void setMark(String mark) {
        this.mark = mark;
    }
}

第三步   在web下的.jsp中写出 首页(index.jsp) ，登录失败页面(error.jsp) ，登录页面(login.jsp)， 注册页面(register.jsp)，主页(zhuye.jsp)，添加页面（addGoods.jsp），修改页面（showGoods）。

1.首页

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/13
  Time: 19:09
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


  


登录
注册

 2.登录页面

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/14
  Time: 10:35
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


    

        账号:

        密码:

           
        没有账号?请注册
    

 3.登录失败页面

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/17
  Time: 19:58
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    


出错啦
返回登录

 4.注册页面

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/14
  Time: 10:35
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    



    账号:

    密码:

    手机号:

    地址:

    确认密码:

       
    已有账号?请登录

 5.登录成功进入的主页面

由后台数据库传递过来的商品数据。

<%

之间可以写服务器端代码

%>

<%=%>获取后台的变量值

   session在网络应用中称为“会话控制”，是服务器为了保存用户状态而创建的一个特殊的对象。简而言之，session就是一个对象，用于存储信息。 

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/17
  Time: 19:35
  To change this template use File | Settings | File Templates.
--%>
<%@taglib prefix="a" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    



欢迎来自${user.address}的${user.uname}访问项目主页

    
    

添加商品

    

    

        
商品编号
        
商品名称
        
商品价格
        
商品说明
    
    
    

    
    
        

            
${goods.gid}
            
${goods.gname}
            
${goods.price}
            
${goods.mark}
            

                修改
                删除
            
        
    
    

6.添加页面

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/25
  Time: 13:36
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    



    商品名称:

    商品价格:

    商品说明:

    

7.修改页面

 

<%--
  Created by IntelliJ IDEA.
  User: chenge
  Date: 2023/2/27
  Time: 8:27
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>


    



商品修改

    商品编号:

    商品名称:

    商品价格:

    商品说明:

    

 第四步 JDBC操作层面

1.在src里建三个包  Dao，httpServlet，Util

 2.在Dao中先创建两个接口 这里起名叫UserDao，GoodsDao

UserDao

login登录页面有两个参数

register 返回一个user对象

package com.chen.Dao;
import com.chen.bean.User;
public interface UserDao {
    /**
     * 完成登陆操作
     * @param uname 用户名
     * @param password 密码
     * @return  数据库查询的用户信息对象
     */
    User login(String uname,String password);
    /**
     * 注册用户
     * @param user  封装的注册信息
     * @return  受影响的行数
     */
    int register(User user);
}

 GoodsDao

这里我们写方法，在impl里GoodsDaoImpl中调用方法。

package com.chen.Dao;
import com.chen.bean.Goods;
import java.util.List;
public interface GoodsDao {
    //全查
    public List slectAll();
    public Goods selectById(int gid);
    //增
    public int selectInsert(Goods goods);
    //删
    public int selectDelete(int gid);
    //改
    public int selectUpdate(Goods goods);
}

3.再在Dao.impl中创建UserDaoImpl类，用这个类去继承UserDao接口，这里面写登录、注册JDBC的操作，用了分层操作，JDBC驱动、连接、调用方法、关闭资源 都在Util包中，httpservlet里写。

        util包-JDBCUtil类

package com.chen.Util;
import com.chen.bean.User;
import java.security.PublicKey;
import java.sql.*;
public class JDBCUtil {
    private static String driver = "com.mysql.cj.jdbc.Driver";
    private static String url = "jdbc:mysql://127.0.0.1:3306/login?useSSL=false&serverTimezone=UTC";
    private static String user = "root";
    private static String password = "root";
    private static Connection conn = null;
    public static Connection getCon() {
        try {
            //1.加载数据库驱动
            Class.forName(driver);
            //2.获取数据库连接
            conn = DriverManager.getConnection(url, user, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return conn;
    }
    //JDBCUtil.getCon()方法
    public static void main(String[] args) {
        System.out.println(JDBCUtil.getCon());
    }
    //登录的关闭资源
    public static void close(ResultSet rs,PreparedStatement pstm,Connection conn) {
        try {
            if (rs!=null){
                rs.close();
            }
            if (pstm!=null){
                pstm.close();
            }
            if (conn!=null){
                conn.close();
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    //注册的关闭资源
    public static void close(PreparedStatement pstm, Connection conn) {
        try {
            if (pstm!=null){
                pstm.close();
            }
            if (conn!=null){
                conn.close();
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

 UserDaoImpl

package com.chen.Dao.imlp;
import com.chen.Dao.UserDao;
import com.chen.Util.JDBCUtil;
import com.chen.bean.User;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class UserDaoImpl implements UserDao {
    User login = null;
    Connection conn = null;  //数据库连接对象
    PreparedStatement pstm = null;  //预处理对象
    ResultSet rs = null;  //结果集对象
    int i = 0;
    //登录
    public User login (String uname, String password){
        try{
            conn = JDBCUtil.getCon();
            //3.sql语句
            String sql = "select * from user where uname=? and password=?";
            //4.获取预处理对象
            pstm = conn.prepareStatement(sql);
            //5.传参
            pstm.setObject(1,uname);
            pstm.setObject(2,password);
            //6.执行查询
            rs = pstm.executeQuery();
            //7.解析结果集
            if (rs.next()){
                login = new User();
                //从结果集中获取数据，封装到实体类对象中
                int uid = rs.getInt("uid");
                login.setId(uid);
                login.setUname(rs.getString("uname"));
                login.setPassword(rs.getString("password"));
                login.setPhone(rs.getString("phone"));
                login.setAddress(rs.getString("address"));
            }
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }finally {
            //8.关闭资源
            JDBCUtil.close(rs,pstm,conn);
        }
        return login;
    }
    @Override
    //注册
    public int register(User user) {
        try {
            conn = JDBCUtil.getCon();
            String sql = "insert into user(uname,password,phone,address) values(?,?,?,?)";
            pstm = conn.prepareStatement(sql);
            pstm.setObject(1,user.getUname());
            pstm.setObject(2,user.getPassword());
            pstm.setObject(3,user.getPhone());
            pstm.setObject(4,user.getAddress());
            i = pstm.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.close(pstm,conn);
        }
        return i;
    }
}

 GoodsDaoImpl

在这里面就要完成全查的操作、添加操作、删除操作、修改操作根据id查找那条数据展现在页面中，再去写sql的修改代码操作。

package com.chen.Dao.imlp;
import com.chen.Dao.GoodsDao;
import com.chen.Util.JDBCUtil;
import com.chen.bean.Goods;
import com.chen.bean.User;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
public class GoodsDaoImpl implements GoodsDao {
    private User login = null;
    private Connection conn = null;  //数据库连接对象
    private PreparedStatement pstm = null;  //预处理对象
    private ResultSet rs = null;  //结果集对象
    private int i = 0; //增删改受影响的行数
//全查
    @Override
    public List slectAll() {
        List goodslist = new ArrayList<>();
        try {
            conn = JDBCUtil.getCon();
            //3.sql语句
            String sql = "select * from goods";
            //4.获取预处理对象
            pstm = conn.prepareStatement(sql);
            //5.执行查询
            rs = pstm.executeQuery();
            Goods goods=null;
            //6.解析结果集
            while (rs.next()){
                goods = new Goods();
                goods.setGid(rs.getInt("gid"));
                goods.setGname(rs.getString("gname"));
                goods.setPrice(rs.getDouble("price"));
                goods.setMark(rs.getString("mark"));
                goodslist.add(goods);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                if (rs!=null){
                    rs.close();
                }
                if (pstm!=null){
                    pstm.close();
                }
                if (conn!=null){
                    conn.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        return goodslist;
}
//模糊查询
  public List seach(String keyword) {
        List goodslist = new ArrayList<>();
        try {
            conn = JDBCUtil.getCon();
            //3.sql语句
            String sql = "select * from goods where gname like concat('%',?,'%')";
            //4.获取预处理对象
            pstm = conn.prepareStatement(sql);
            pstm.setObject(1,keyword);
            //5.执行查询
            rs = pstm.executeQuery();
            //6.解析结果集
            while (rs.next()){
                goods = new Goods();
                goods.setGid(rs.getInt("gid"));
                goods.setGname(rs.getString("gname"));
                goods.setPrice(rs.getDouble("price"));
                goods.setMark(rs.getString("mark"));
                goodslist.add(goods);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                if (rs!=null){
                    rs.close();
                }
                if (pstm!=null){
                    pstm.close();
                }
                if (conn!=null){
                    conn.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        return goodslist;
    }
//id查询
 public Goods selectById(int gid){
        Goods goods = null;
        try {
            conn = JDBCUtil.getCon();
            //3.sql语句
            String sql = "select * from goods where gid=?";
            //4.获取预处理对象
            pstm = conn.prepareStatement(sql);
            pstm.setObject(1,gid);
            //5.执行查询
            rs = pstm.executeQuery();
            //6.解析结果集
            if (rs.next()){
                goods = new Goods();
                goods.setGid(rs.getInt("gid"));
                goods.setGname(rs.getString("gname"));
                goods.setPrice(rs.getDouble("price"));
                goods.setMark(rs.getString("mark"));
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                if (rs!=null){
                    rs.close();
                }
                if (pstm!=null){
                    pstm.close();
                }
                if (conn!=null){
                    conn.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        return goods;
    }
//添加数据
    @Override
    public int selectInsert(Goods goods) {
            try {
                conn = JDBCUtil.getCon();
                //3.sql语句
                String sql = "insert into goods(gname,price,mark) values (?,?,?)";
                //4.获取预处理对象
                pstm = conn.prepareStatement(sql);
                pstm.setObject(1,goods.getGname());
                pstm.setObject(2,goods.getPrice());
                pstm.setObject(3,goods.getMark());
                //5.执行查询
                i = pstm.executeUpdate();
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                try {
                    if (pstm!=null){
                        pstm.close();
                    }
                    if (conn!=null){
                        conn.close();
                    }
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
            return i;
    }
//删除
    @Override
    public int selectDelete(int gid) {
        System.out.println("selectDelete");
            try {
                conn = JDBCUtil.getCon();
                //3.sql语句
                String sql = "delete  from goods where gid=?";
                //4.获取预处理对象
                pstm = conn.prepareStatement(sql);
                pstm.setObject(1,gid);
                //5.执行查询
                i = pstm.executeUpdate();
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                try {
                    if (pstm!=null){
                        pstm.close();
                    }
                    if (conn!=null){
                        conn.close();
                    }
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
            return i;
    }
//修改
    @Override
    public int selectUpdate(Goods goods) {
        try {
            conn = JDBCUtil.getCon();
            //3.sql语句
            String sql = "update goods set gname=?,price=?,mark=? where gid=?";
            //4.获取预处理对象
            pstm = conn.prepareStatement(sql);
            pstm.setObject(1,goods.getGname());
            pstm.setObject(2,goods.getPrice());
            pstm.setObject(3,goods.getMark());
            pstm.setObject(4,goods.getGid());
            //5.执行查询
            i = pstm.executeUpdate();
            System.out.println("i="+i);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try {
                if (pstm!=null){
                    pstm.close();
                }
                if (conn!=null){
                    conn.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        return i;
    }
}

 第五步 业务处理层面

httpServlet中写的三个类是处理 ：

1.设置请求和响应的编码格式
2.获取请求的参数
3.执行业务处理

Login

1.映射地址

@WebServlet("/login")

请求：

request.getRequestDispatcher("        ").forward(request,response);//请求别的地址

package com.chen.httpServlet;
import com.chen.Dao.UserDao;
import com.chen.Dao.imlp.UserDaoImpl;
import com.chen.bean.User;
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 java.io.IOException;
@WebServlet("/login")
public class Login extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("Login-get");
        doPost(request,response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("Login-post");
        //前端请求（request），后端处理后，最后给前端做出响应（response）
        //1.设置请求和响应的编码格式，以及响应的格式
        request.setCharacterEncoding("utf-8");  //设置请求的编码格式为中文
        response.setCharacterEncoding("utf-8");    //设置响应的编码格式
        response.setContentType("text/html;charset=UTF-8");  //以什么样的格式 （文本/网页）响应
        //2.获取请求的参数
        String uname = request.getParameter("uname"); //根据表单的name属性获取用户输入的值
        String password = request.getParameter("password");
        //3.执行业务处理
        UserDao userDao = new UserDaoImpl();
        User login = userDao.login(uname,password);
        //判断登录的用户信息是否为空
        if (login!=null) {
            System.out.println("登录成功！");
            //登录成功,当前servlet的业务处理完毕----后续执行查询商品的操作应该由别人来完成---请求转发给别的servlet处理
            request.getRequestDispatcher("selectAllGoods").forward(request,response);//请求别的地址
        } else {
            //登录失败，跳转到错误页
            response.sendRedirect("error.jsp");
        }
    }
}

 Register

1.映射地址

@WebServlet("/register")

package com.chen.httpServlet;
import com.chen.Dao.UserDao;
import com.chen.Dao.imlp.UserDaoImpl;
import com.chen.bean.User;
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 java.io.IOException;
import java.sql.*;
@WebServlet("/register")
public class Register extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("register-get");
        doPost(request,response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("register-post");
        //1.设置请求和响应的编码格式，以及响应的格式
        request.setCharacterEncoding("utf-8");  //设置请求的编码格式为中文
        response.setCharacterEncoding("utf-8");    //设置响应的编码格式
        //2.获取请求的参数
        String uname = request.getParameter("uname"); //根据表单的name属性获取用户输入的值
        String password = request.getParameter("password");
        String phone = request.getParameter("phone");
        String address = request.getParameter("address");
        //封装：把上面所有的变量装载到User对象中
        User user = new User();
        user.setUname(uname);
        user.setPassword(password);
        user.setPhone(phone);
        user.setAddress(address);
        System.out.println(user);
        //3.执行业务处理
        UserDao userDao = new UserDaoImpl();
        int i = userDao.register(user);
        //判断登录的用户信息是否为空
        if (i > 0) {
            //注册成功，跳转到登录页面
            response.sendRedirect("login.jsp");//指定跳转的页面
        } else {
            //登录失败，跳转到错误页
            response.sendRedirect("register.jsp");
        }
    }
}

 SelectAllGoods

1.映射地址

@WebServlet("/selectAllGoods")

//通过request获取session对象，该对象可以向前端传递传输数据的容器HttpSession               session = req.getSession();

package com.chen.httpServlet;
import com.chen.Dao.imlp.GoodsDaoImpl;
import com.chen.bean.Goods;
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.util.List;
@WebServlet("/selectAllGoods")
public class SelectAllGoods extends HttpServlet {
    @Override
    protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("SelectAllGoods..dopost");
        //查询所有商品信息
        GoodsDaoImpl goodsDao = new GoodsDaoImpl();
        List goodsList = goodsDao.slectAll();
        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递传输数据的容器
        HttpSession session = req.getSession();
        //向session 中存入商品信息集合
        session.setAttribute("goodsList", goodsList);
        //登录成功，跳转到主页
        resp.sendRedirect("zhuye.jsp");//指定的跳转页面
    }
}

InsertGoods

1.映射地址

@WebServlet("/addGoods")

package com.chen.httpServlet;
import com.chen.Dao.GoodsDao;
import com.chen.Dao.imlp.GoodsDaoImpl;
import com.chen.bean.Goods;
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 java.io.IOException;
@WebServlet("/addGoods")
public class InsertGoods extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        //获取请求参数并封装到Goods对象中
        Goods goods = new Goods();
        goods.setGname(req.getParameter("gname"));
        //使用Double包装类把req.getParameter获取到字符串数字 转换为 double类型的数据
        goods.setPrice(Double.parseDouble(req.getParameter("price")));
        goods.setMark(req.getParameter("mark"));
        //执行JDBC的添加操作
        GoodsDao goodsDao = new GoodsDaoImpl();
        int i = goodsDao.selectInsert(goods);
        if (i > 0) {
            //添加成功
            req.getRequestDispatcher("selectAllGoods").forward(req, resp);
        } else {
            //添加失败
            req.setAttribute("error_msg", "添加商品出错了!");
            req.getRequestDispatcher("error.jsp").forward(req, resp);
        }
    }
}

 DeleteGoods

1.映射地址

@WebServlet("/del")

package com.chen.httpServlet;
import com.chen.Dao.GoodsDao;
import com.chen.Dao.imlp.GoodsDaoImpl;
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 java.io.IOException;
@WebServlet("/del")
public class DeleteGoods extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int gid = Integer.parseInt(req.getParameter("gid"));
        //根据id执行数据库的删除
        GoodsDao goodsDao = new GoodsDaoImpl();
        int i = goodsDao.selectDelete(gid);
        if (i>0){
            //请求转发，查讯所有商品信息（刷新）
            req.getRequestDispatcher("selectAllGoods").forward(req,resp);
        }else {
            req.setAttribute("error_msg","删除出现了问题!");
            req.getRequestDispatcher("error.jsp").forward(req,resp);
        }
    }
}

FindByIdGoods 

1.映射地址

@WebServlet("/findById")

package com.chen.httpServlet;
import com.chen.Dao.GoodsDao;
import com.chen.Dao.imlp.GoodsDaoImpl;
import com.chen.bean.Goods;
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 java.io.IOException;
@WebServlet("/findById")
public class FindByIdGoods extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        int gid = Integer.parseInt(req.getParameter("gid"));
        //根据gid查询商品信息
        GoodsDao goodsDao = new GoodsDaoImpl();
        Goods goods = goodsDao.selectById(gid);
        if (goods!= null){
            //把数据存储到req域对象中，然后请求转发到页面
            req.setAttribute("goods",goods);
            req.getRequestDispatcher("showGoods.jsp").forward(req,resp);
        }else {
            //登录失败，跳转到错误页
            req.setAttribute("error_msg","修改出现异常!");
            req.getRequestDispatcher("error.jsp").forward(req,resp);
        }
    }
}

UpdateGoods

1.映射地址

@WebServlet("/updateGoods")

package com.chen.httpServlet;
import com.chen.Dao.GoodsDao;
import com.chen.Dao.UserDao;
import com.chen.Dao.imlp.GoodsDaoImpl;
import com.chen.Dao.imlp.UserDaoImpl;
import com.chen.bean.Goods;
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 java.io.IOException;
@WebServlet("/updateGoods")
public class UpdateGoods extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.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(req.getParameter("gid")));
        goods.setGname(req.getParameter("gname"));
        goods.setPrice(Double.parseDouble(req.getParameter("price")));
        goods.setMark(req.getParameter("mark"));
        //执行数据库的修改操作
       GoodsDao goodsDao = new GoodsDaoImpl();
        goodsDao.selectUpdate(goods)
        if (i>0){
            //请求转发，查讯所有商品信息（刷新）
            req.getRequestDispatcher("selectAllGoods").forward(req,resp);
        }else {
            req.setAttribute("error_msg","修改失败，请重新尝试!");
            req.getRequestDispatcher("error.jsp").forward(req,resp);
        }
    }
}

Seach

@WebServlet("/seach")

package com.chen.httpServlet;
import com.chen.Dao.GoodsDao;
import com.chen.Dao.imlp.GoodsDaoImpl;
import com.chen.bean.Goods;
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.util.List;
@WebServlet("/seach")
public class Seach extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        String keyword = req.getParameter("keyword");
        //根据关键词执行JDBC的模糊查询
        GoodsDao goodsDao = new GoodsDaoImpl();
        List goodsList = goodsDao.seach(keyword);
        //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递传输数据的容器
        HttpSession session = req.getSession();
        //向session 中存入商品信息集合
        session.setAttribute("goodsList", goodsList);
        //登录成功，跳转到主页
        resp.sendRedirect("zhuye.jsp");//指定的跳转页面
    }
}

到这里代码就结束了，数据库原本的三条数据，正确的账号密码。

如果注册，注册的信息就存在后台的数据库里，如果注册成功就可以登录成功,在后台数据库里添加商品信息，通过session在主页页面中就能看到商品信息。增删改查操作。

不能随意访问网址就能进入注册、添加、主页页面中，所以我们要写个过滤器，防止外来人员直接访问。

第六步 Filter过滤器

1、filter简介

Filter中文意思为过滤器。顾名思义，过滤器可在浏览器以及目标资源之间起到一个过滤的作用。例如:水净化器，可以看成是生活中的一个过滤器，他可以将污水中的杂质过滤，从而使进入的污水变成净水。对于WEB应用来说，过滤器是一个驻留在服务器中的WEB组件，他可以截取客户端和WEB资源之间的请求和响应信息。WEB资源可能包括ServletJSPHTML页面等。

Filter是Tomcat容器内的过滤器，在请求到达容器是先会调用过滤器，再调用我们的servlet或者jsp。

当服务器收到特定的请求后，会先将请求交给过滤器，程序员可以在过滤器中对请求信息进行读取修改等操作，然后将请求信息再发送给目标资源。目标资源作出响应后，服务器会再次将响应转交给过滤器，在过滤器中同样可以对响应信息做一些操作，然后再将响应发送给浏览器。

也就是说过滤器可以在WEB资源收到请求之前，浏览器收到响应之前，对请求和响应信息做一些相应的操作。

在一个WEB应用中可以部署多个过滤器，多个过滤器就组成了一个过滤器链，请求和响应必须在经过多个过滤器后才能到达目标。

过滤器不是必须将请求传送到下一个过滤器(或WEB资源)，也可以自己来处理请求，发送响应。

2、filter的实现

 Filter接口，实现Filter需要实现该接口

1、init()方法用于初始化Filter。

2、doFilter()作用和service()方法类似，是过滤请求和响应的主要方法。

3、destroy0用于在Filter对象被销毁前做一些收尾工作。如:释放资源等

3、filter的生命周期

Filter的生命周期和Servlet类似

构造器:创建Filter实例是调用，Filter实例服务器一旦启动就会被创建

init():实例创建后马上被调用，用来对Filter做一些初始化的操作

doFilter():Filter的主要方法，用来完成过滤器主要功能的方法，每次访问目标资源时都会调用。

destroy():服务器停止时调用，用来释放资源

首先

映射所有

@WebFilter("/*")

实现filter接口

 

 因为要登录（+登录的映射地址），没有账号的要注册（+注册的映射地址），登陆失败跳转错误页面，这些页面都需要放行，直接访问主页会回到登录页面。

具体代码如下：

package com.chen.filter;
import com.chen.bean.User;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
@WebFilter("/*")
public class MyFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("初始化..");
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //1.在过滤器中把servletRequest、servletResponse转换为HttpServletRequest、HttpServletResponse
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        //2.获取请求的资源路径
        String servletPath = request.getServletPath();
        //3.获取session储存的用户对象
        HttpSession session = request.getSession();
        User user = (User) session.getAttribute("user");
        //4.1如果请求index.jsp、login.jsp、login、register.jsp、register、error.jsp则放行
        if (servletPath.equals("/index.jsp") ||servletPath.equals("/login.jsp") ||servletPath.equals("/login") ||servletPath.equals("/register.jsp") ||servletPath.equals("/register") ||servletPath.equals("/error.jsp")){
            filterChain.doFilter(servletRequest,servletResponse);//放行
        }else if (user!=null){
            filterChain.doFilter(servletRequest,servletResponse);//放行
        }else {
            response.sendRedirect("login.jsp");
        }
    }
    @Override
    public void destroy() {
        System.out.println("销毁..");
    }
}

项目效果如下：