MVC模式 和 三层架构——应用案例

目录

1.环境准备

2.创建工程  

3.创建包

4.创建表

5.创建实体类

6.准备mybatis环境

7.查询所有

7.1编写BrandMapper

7.2编写工具类

7.3编写BrandService

7.4编写Servlet

7.5编写brand.jsp页面

8.其余代码下载：

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1.环境准备

环境准备工作，我们分以下步骤实现：

• 创建新的模块 brand_demo，引入坐标

• 创建三层架构的包结构

• 数据库表 tb_brand

• 实体类 Brand

• MyBatis 基础环境

  • Mybatis-config.xml

  • BrandMapper.xml

  • BrandMapper接口

2.创建工程  

创建新的模块 brand_demo，引入坐标。我们只要分析出要用到哪儿些技术，那么需要哪儿些坐标也就明确了

• 需要操作数据库。mysql的驱动包

• 要使用mybatis框架。mybaits的依赖包

• web项目需要用到servlet和jsp。servlet和jsp的依赖包

• 需要使用 jstl 进行数据展示。jstl的依赖包

pom.xml 内容如下：

<?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">
    <parent>
        <artifactId>test</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>brand-demo</artifactId>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.34</version>
        </dependency>

        <!--servlet-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <scope>provided</scope>
        </dependency>

        <!--jsp-->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2</version>
            <scope>provided</scope>
        </dependency>

        <!--jstl,JSP标准标签库-->
        <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>

3.创建包

创建不同的包结构，用来存储不同的类。包结构如下

 4.创建表

-- 删除tb_brand表
drop table if exists tb_brand;
-- 创建tb_brand表
create table tb_brand
(
    -- id 主键
    id           int primary key auto_increment,
    -- 品牌名称
    brand_name   varchar(20),
    -- 企业名称
    company_name varchar(20),
    -- 排序字段
    ordered      int,
    -- 描述信息
    description  varchar(100),
    -- 状态：0：禁用  1：启用
    status       int
);
-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
       ('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1),
       ('小米', '小米科技有限公司', 50, 'are you ok', 1);

5.创建实体类

在 pojo 包下创建名为 Brand 的类。

package com.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 +
                '}';
    }
}

6.准备mybatis环境

定义核心配置文件 Mybatis-config.xml ，并将该文件放置在 resources 下

<?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.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                //数据库地址
                <property name="url" value="jdbc:mysql://localhost:13306/db1"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--扫描mapper-->
        <package name="com.mapper"/>
    </mappers>
</configuration>

在 resources 下创建放置映射配置文件的目录结构 com/mapper(注意：这个包名创建时只能使用"/"，不能使用"."，xml和原文件包的结构应该一样)，并在该目录下创建映射配置文件 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.mapper.BrandMapper">

    <resultMap id="brandResultMap" type="brand">
        <result column="brand_name" property="brandName"></result>
        <result column="company_name" property="companyName"></result>
    </resultMap>

    <insert id="add">
        insert into tb_brand values(null,#{brandName},#{companyName},#{ordered},#{description},#{status});
    </insert>

    <update id="update">
        update tb_brand set brand_name=#{brandName},company_name=#{companyName},ordered=#{ordered},
                            description=#{description},status=#{status} where id=#{id};
    </update>

    <delete id="delete">
        delete from tb_brand where id=#{id};
    </delete>

    <select id="selectAll" resultMap="brandResultMap">
        select * from tb_brand;
    </select>

    <select id="selectByIdBrand"  resultMap="brandResultMap">
        select * from tb_brand where id=#{id};
    </select>

</mapper>

7.查询所有

当我们点击 index.html 页面中的 查询所有 这个超链接时，就能查询到上图右半部分的数据。

对于上述的功能，点击 查询所有 超链接是需要先请后端的 servlet ，由 servlet 跳转到对应的页面进行数据的动态展示。而整个流程如下图：

 7.1编写BrandMapper

 在 mapper 包下创建创建 BrandMapper 接口，在接口中定义 selectAll() 方法

List<Brand> selectAll();

7.2编写工具类

在 com 包下创建 utils 包，并在该包下创建名为 SqlSessionFactoryUtils 工具类

package com.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;
    }
}

7.3编写BrandService

 在 service 包下创建 BrandService 类

package com.service;

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

import java.util.List;

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

//    查询所有
    public List<Brand> selectAll(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

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

        sqlSession.close();

        return brands;
    }

//    添加数据
    public void add(Brand brand)
    {
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        mapper.add(brand);

//        增删改需要提交事务才能正常进行，查询不需要
        sqlSession.commit();

        sqlSession.close();
    }

    //按照id查询
    public Brand selectById(int id){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        Brand brand = mapper.selectByIdBrand(id);

        sqlSession.close();

        return brand;
    }

    //修改
    public void Update(Brand brand){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        mapper.update(brand);

        sqlSession.commit();

        sqlSession.close();
    }

    //删除
    public void Delete(Brand brand){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        BrandMapper mapper = sqlSession.getMapper(BrandMapper.class);

        mapper.delete(brand);

        sqlSession.commit();

        sqlSession.close();
    }
}

7.4编写Servlet

在 web 包下创建名为 SelectAllServlet 的 servlet，该 servlet 的逻辑如下：

• 调用 BrandService 的 selectAll() 方法进行业务逻辑处理，并接收返回的结果

• 将上一步返回的结果存储到 request 域对象中

• 跳转到 brand.jsp 页面进行数据的展示

具体的代码如下

package com.web;

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

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

@WebServlet(name = "SelectAllServlet", value = "/SelectAllServlet")
public class SelectAllServlet extends HttpServlet {
    private BrandService brandService = new BrandService();

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        BrandService brandService = new BrandService();
        List<Brand> brands = brandService.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);
    }
}

7.5编写brand.jsp页面

 在brand.jsp 页面在表格中使用 JSTL 和 EL表达式 从request域对象中获取名为 brands 的集合数据并展示出来。页面内容如下：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ page isELIgnored="false" %>
<html>
<head>
    <title>显示页面</title>
</head>
<body>
<input type="button" value="新增" id="add"><br>
   <table border="1px">
    <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="${brands}" var="brand">
        <tr align="center"bgcolor="#ffc0cb">
            <td>${brand.id}</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>禁止</td>
            </c:if>
            <td><a href="/brand-demo/selectByIdServlet?id=${brand.id}">修改</a> <a href="/brand-demo/DeleteServlet?id=${brand.id}">删除</a></td>
        </tr>
    </c:forEach>
   </table>

<script>
    document.getElementById("add").onclick=function (){
        location.href="/brand-demo/AddBrand.jsp";
    }
</script>

</body>
</html>

8.其余代码下载：

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