使用MVC三层架构实现对数据库表的增删改查操作（全部代码）

使用MVC三层架构实现对数据库表的增删改查操作（全部代码）

一.环境：

1.idea：2021
2.jdk：1.8
3.maven：apache-maven-3.6.1
4.tomcat：tomcat 8.5.4

二.项目结构

三.编写的思路

1.准备工作：

2.实现增删改查思路：

3:提供一个看懂的思路
（1）创建一个工程/模块（webapp）；
（2）准备一个数据库db1，里面有一张表brand（上面图那样的）；
（3）创建三层架构的包结构：mapper（dao）数据库
service
web
以及实体类包（pojo）和工具类包(util)，并且将代码复制进去（下面有源代码）
（4）配置mybatis的环境(上面有张图)
（5）开始查询操作：页面上有一个超链接"查询所有"，点进去后在另一个界面的表单上显示查询到的表
怎么写呢？
思路如下：
1.在BrandMapper写查询方法，用注解的方式；
2.在BrandService里面实现这个方法；
3.在SelectAllServlet里面用service调用查询方法，转到查询后的界面（其中包括几个jsp页面数据的接收）
其他逻辑比它稍微复杂一点点，大差不差！
（6）需要注意的部分：
1.乱码的处理；
2.命名结构不一致；
3.除了查询，其他事务都需要提交；
（7）效果：(放在最后啦)
（8）看不懂的话：联系我！！！

四.代码

BrandMapper

package com.itheima.mapper;

import com.itheima.pojo.Brand;
import org.apache.ibatis.annotations.*;

import java.util.List;

public interface BrandMapper {
    
    
    /**
     * 查询所有
     * @return
     */
    @Select("select * from tb_brand")
    @ResultMap("brandResultMap")//解决不同名问题
    List<Brand> selectAll();

    /**
     * 插入
     * @param brand
     */
    @Insert("insert into tb_brand values(null,#{brandName},#{companyName},#{ordered},#{description},#{status})")
    void add( Brand brand);

    /**
     * 根据id查
     * @param id
     * @return
     */
    @Select("select * from tb_brand where id=#{id}")
    @ResultMap("brandResultMap")//解决不同名问题
    Brand selectById(int id);

    /**
     * 修改
     * @param brand
     */
    @Update("update tb_brand set brand_name = #{brandName},company_name = #{companyName},ordered = #{ordered},description = #{description},status = #{status} where id = #{id}")
    void update(Brand brand);

    /**
     * 根据id删除
     */
    @Delete("delete from tb_brand where id=#{id}")
    void  deleteById(int id);
}

**Brand **

package com.itheima.pojo;
/**
 * 品牌实体类
 */
public class Brand {
    
    
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    private Integer status;


    public Brand() {
    
    
    }

    public Brand(Integer id, String brandName, String companyName, String description) {
    
    
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.description = description;
    }

    public Brand(Integer id, String brandName, String companyName, Integer ordered, String description, Integer status) {
    
    
        this.id = id;
        this.brandName = brandName;
        this.companyName = companyName;
        this.ordered = ordered;
        this.description = description;
        this.status = status;
    }

    public Integer getId() {
    
    
        return id;
    }

    public void setId(Integer id) {
    
    
        this.id = id;
    }

    public String getBrandName() {
    
    
        return brandName;
    }

    public void setBrandName(String brandName) {
    
    
        this.brandName = brandName;
    }

    public String getCompanyName() {
    
    
        return companyName;
    }

    public void setCompanyName(String companyName) {
    
    
        this.companyName = companyName;
    }

    public Integer getOrdered() {
    
    
        return ordered;
    }

    public void setOrdered(Integer ordered) {
    
    
        this.ordered = ordered;
    }

    public String getDescription() {
    
    
        return description;
    }

    public void setDescription(String description) {
    
    
        this.description = description;
    }

    public Integer getStatus() {
    
    
        return status;
    }

    public void setStatus(Integer status) {
    
    
        this.status = status;
    }

    @Override
    public String toString() {
    
    
        return "Brand{" +
                "id=" + id +
                ", brandName='" + brandName + '\'' +
                ", companyName='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }
}

**BrandService **

package com.itheima.service;

import com.itheima.mapper.BrandMapper;
import com.itheima.pojo.Brand;
import com.itheima.util.SqlSessionFactoryUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.List;

public class BrandService {
    
    
    SqlSessionFactory factory= SqlSessionFactoryUtils.getSqlSessionFactory();

    /**
     * 查询所有
     * @return
     */
    public List<Brand> selectAll(){
    
    
        //调用BrandMapper的selectAll()

        //2.获取 sqlSession对象
        SqlSession sqlSession=factory.openSession();
        //3.获取BrandMapper
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
        //4.调用方法
        List<Brand> brands = mapper.selectAll();

        sqlSession.close();

        return brands;

    }

    /**
     * 新增
     * @param brand
     */
    public void add(Brand brand){
    
    
        SqlSession sqlSession = factory.openSession();

        BrandMapper mapper=sqlSession.getMapper(BrandMapper.class);

        mapper.add(brand);
        sqlSession.commit();

        sqlSession.close();

    }

    /**
     * 根据id查
     * @param id
     * @return
     */
    public Brand selectById(int id){
    
    
        SqlSession sqlSession = factory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
        Brand brand = mapper.selectById(id);
        sqlSession.close();
        return brand;
    }

    /**
     * 修改
     * @param brand
     */
    public void update(Brand brand){
    
    
        SqlSession sqlSession = factory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
        mapper.update(brand);
        sqlSession.commit();
        sqlSession.close();
    }

    public void deleteById(int id){
    
    
        SqlSession sqlSession = factory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);
        mapper.deleteById(id);
        sqlSession.commit();
        sqlSession.close();
    }
}

**SqlSessionFactoryUtils **

package com.itheima.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {
    
    

    private static SqlSessionFactory sqlSessionFactory;

    static {
    
    
        //静态代码块会随着类的加载而自动执行，且只执行一次

        try {
    
    
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
    
    
            e.printStackTrace();
        }
    }


    public static SqlSessionFactory getSqlSessionFactory(){
    
    
        return sqlSessionFactory;
    }
}

**AddServlet **

package com.itheima.web;

import com.itheima.pojo.Brand;
import com.itheima.service.BrandService;

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

@WebServlet("/addServlet")
public class AddServlet extends HttpServlet {
    
    
    private BrandService service=new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //处理post请求乱码问题
        request.setCharacterEncoding("utf-8");

        //1.接收表单提交的数据
        String brandName = request.getParameter("brandName");
        String companyName = request.getParameter("companyName");
        String ordered = request.getParameter("ordered");
        String description = request.getParameter("description");
        String status = request.getParameter("status");

        Brand brand=new Brand();
        brand.setBrandName(brandName);
        brand.setCompanyName(companyName);
        brand.setOrdered(Integer.parseInt(ordered));
        brand.setDescription(description);
        brand.setStatus(Integer.parseInt(status));
        //2.调用service完成添加
        service.add(brand);

        //3.转发到查询所有的servlet
        request.getRequestDispatcher("/selectAllServlet").forward(request,response);


    }

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

**DeleteByIdServlet **

package com.itheima.web;

import com.itheima.pojo.Brand;
import com.itheima.service.BrandService;

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.util.List;

@WebServlet("/deleteByIdServlet")
public class DeleteByIdServlet extends HttpServlet {
    
    
    private BrandService service=new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //1.接收数据id
        String id = request.getParameter("id");
        //2.调用service方法
        service.deleteById(Integer.parseInt(id));

        List<Brand> brands = service.selectAll();

        request.setAttribute("brands",brands);
        request.getRequestDispatcher("/brand.jsp").forward(request,response);


    }

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

**SelectAllServlet **

package com.itheima.web;

import com.itheima.pojo.Brand;
import com.itheima.service.BrandService;

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

@WebServlet("/selectAllServlet")
public class SelectAllServlet extends HttpServlet {
    
    
    BrandService service = new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //1.调用BrandService完成查询

        List<Brand> brands = service.selectAll();

        //2.存入request中
        request.setAttribute("brands",brands);

        //3.转发到brands.jsp
        request.getRequestDispatcher("/brand.jsp").forward(request,response);

    }

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

**SelectByIdServlet **

package com.itheima.web;

import com.itheima.pojo.Brand;
import com.itheima.service.BrandService;

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

@WebServlet("/selectByIdServlet")
public class SelectByIdServlet extends HttpServlet {
    
    
    private BrandService service=new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //1.接收数据id
        String id = request.getParameter("id");
        //2.调用service方法查询
        Brand brand = service.selectById(Integer.parseInt(id));
        //3.存到request域里
        request.setAttribute("brand",brand);
        //转发到一个表单update,jsp
        request.getRequestDispatcher("/brand.jsp").forward(request,response);
    }

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

**UpdateServlet **

package com.itheima.web;

import com.itheima.pojo.Brand;
import com.itheima.service.BrandService;

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("/updateServlet")
public class UpdateServlet extends HttpServlet {
    
    
    private BrandService service=new BrandService();
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //处理post请求乱码问题
        request.setCharacterEncoding("utf-8");

        //1.接收表单提交的数据
        String id=request.getParameter("id");
        String brandName = request.getParameter("brandName");
        String companyName = request.getParameter("companyName");
        String ordered = request.getParameter("ordered");
        String description = request.getParameter("description");
        String status = request.getParameter("status");

        Brand brand=new Brand();
        brand.setId(Integer.parseInt(id));
        brand.setBrandName(brandName);
        brand.setCompanyName(companyName);
        brand.setOrdered(Integer.parseInt(ordered));
        brand.setDescription(description);
        brand.setStatus(Integer.parseInt(status));
        //2.调用service完成修改
        service.update(brand);

        //3.转发到查询所有的servlet
       request.getRequestDispatcher("/selectAllServlet").forward(request,response);
    }

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

BrandMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.BrandMapper">


<!--解决属性名和数据库名字不一样查不出来的问题-->
    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>
</mapper>

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--起别名-->
    <typeAliases>
        <package name="com.itheima.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///db1?useSSL=false&amp;useServerPrepStmts=true"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--扫描mapper-->
        <package name="com.itheima.mapper"/>
    </mappers>
</configuration>

addBrand.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>添加品牌</title>
</head>
<body>
<h3>添加品牌</h3>
<form action="/brand-demo1/addServlet" method="post">
    品牌名称：<input name="brandName"><br>
    企业名称：<input name="companyName"><br>
    排序：<input name="ordered"><br>
    描述信息：<textarea rows="5" cols="20" name="description"></textarea><br>
    状态：
    <input type="radio" name="status" value="0">禁用
    <input type="radio" name="status" value="1">启用<br>

    <input type="submit" value="提交">
</form>
</body>
</html>

brand.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="button" value="新增" id="add"><br>
<hr>
<table border="1" cellspacing="0" width="80%">
    <tr>
        <th>序号</th>
        <th>品牌名称</th>
        <th>企业名称</th>
        <th>排序</th>
        <th>品牌介绍</th>
        <th>状态</th>
        <th>操作</th>

    </tr>


    <c:forEach items="${brands}" var="brand" varStatus="status">
        <tr align="center">
            <%--<td>${
    
    brand.id}</td>--%>
            <td>${
    
    status.count}</td>
            <td>${
    
    brand.brandName}</td>
            <td>${
    
    brand.companyName}</td>
            <td>${
    
    brand.ordered}</td>
            <td>${
    
    brand.description}</td>
            <c:if test="${brand.status == 1}">
                <td>启用</td>
            </c:if>
            <c:if test="${brand.status != 1}">
                <td>禁用</td>
            </c:if>

            <td><a href="/brand-demo1/selectByIdServlet?id=${brand.id}">修改</a> <a href="/brand-demo1/deleteByIdServlet?id=${brand.id}">删除</a></td>
        </tr>

    </c:forEach>

</table>

<script>
    document.getElementById("add").onclick=function (){
    
    
        location.href="/brand-demo1/addBrand.jsp";
    }
</script>
</body>
</html>

update.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>修改品牌</title>
</head>
<body>
<h3>修改品牌</h3>
<form action="/brand-demo1/updateServlet" method="post">

    <%--隐藏域，提交id--%>
    <input type="hidden" name="id" value="${brand.id}">

    品牌名称：<input name="brandName" value="${brand.brandName}"><br>
    企业名称：<input name="companyName" value="${brand.companyName}"><br>
    排序：<input name="ordered" value="${brand.ordered}"><br>
    描述信息：<textarea rows="5" cols="20" name="description">${
    
    brand.description} </textarea><br>
    状态：
    <c:if test="${brand.status == 0}">

        <input type="radio" name="status" value="0" checked>禁用
        <input type="radio" name="status" value="1">启用<br>
    </c:if>

    <c:if test="${brand.status == 1}">

        <input type="radio" name="status" value="0" >禁用
        <input type="radio" name="status" value="1" checked>启用<br>
    </c:if>
    <input type="submit" value="提交">
</form>
</body>
</html>

pom.xml

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>brand-demo1</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>brand-demo1 Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <maven.compiler.source>8</maven.compiler.source>
    <maven.compiler.target>8</maven.compiler.target>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.5</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.34</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>3.1.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.2</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>taglibs</groupId>
      <artifactId>standard</artifactId>
      <version>1.1.2</version>
    </dependency>

  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.tomcat.maven</groupId>
        <artifactId>tomcat7-maven-plugin</artifactId>
        <version>2.2</version>
      </plugin>
    </plugins>
  </build>

</project>

效果：

点击查询所有------>

点击修改----->

修改后提交----->

点击左上角新增按钮----->

点击提交------>

点击删除------->