🍁博客主页：👉 不会压弯的小飞侠
✨欢迎关注：👉点赞👍收藏⭐留言✒
✨系列专栏：👉 MyBatis详解
✨如果觉得博主的文章还不错的话，请三连支持一下博主。
🔥欢迎大佬指正，一起 学习！一起加油！

@TOC

一、代理开发方式

• 采用Mybatis的代理开发方式实现DAO层的开发，这种方式是我们后面进入企业的主流。
• Mapper接口开发方法只需要程序员编写Mapper接口(相当于Dao接口)，由Mybatis框架根据接口定义创建接口
• 动态代理对象，代理对象的方法体同上边Dao接口实现类方法。

• Mapper接口开发需要遵循以下规范:

  • 1、Mapper.xml文件中的namespace与mapper接口的全限定名相同
  • 2、Mapper接口方法名和Mapper.xml中定义的每个statement的id相同
  • 3、Mapper接口方法的输入参数类型和mapper.xml中定义的每个sql的parameterType的类型相同4、Mapper接口方法的输出参数类型和mapper.xml中定义的每个sql的resultType的类型相同

二、案例分析

1.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>MyBatis-Dao</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.32</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>
</project>

2.jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatisthree
jdbc.username=root
jdbc.password=root

3.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 core file-->
       <configuration>
    <!--通过properties标签添加properties文件-->
    <properties resource="jdbc.properties"></properties>
    <!--自定义别名-->
    <typeAliases>
        <typeAlias type="com.study.domain.User" alias="user"></typeAlias>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--加载sql映射文件-->
    <mappers>
        <mapper resource="com/study/dao/UserMapper.xml"/>
    </mappers>
</configuration>

4.User

package com.study.domain;

public class User {
    private int id;
    private String username;
    private String password;

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

5.UserMapper

package com.study.dao;

import com.study.domain.User;

import javax.jws.soap.SOAPBinding;
import java.util.List;

public interface UserMapper {
    public List<User> findAll();
    public User findById(int id);
}

6.UserMapper.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.study.dao.UserMapper">
    <!-- 查询-->
    <select id="findAll" resultType="user">
        select * from user
    </select>
    <!--根据id查询-->
    <select id="findById" parameterType="int" resultType="user">
        select * from user where id=#{id}
    </select>
</mapper>

7.MyBatisTest

package com.study.ServiceTest;

import com.study.dao.UserMapper;
import com.study.domain.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import javax.annotation.Resource;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MyBatisTest {
    public static void main(String[] args) throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> all = mapper.findAll();
        System.out.println(all);
        //[User{id=1, username='小马哥', password='111111'}, User{id=2, username='小飞侠', password='222222'},
        // User{id=3, username='马奎斯', password='333333'}, User{id=4, username='罗西', password='444444'}]

        //根据id查询
        User user = mapper.findById(3);
        System.out.println(user);
        //User{id=3, username='马奎斯', password='333333'}
    }
}