Mybatis的Dao层实现:代理开发方式

代理开发方式只要写好接口就行了，不需要像传统实现方式那样自己去实现接口，由Mybatis 框架根据接口定义创建接口的动态代理对象

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

编写映射文件mapper.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.dao.UserMapper">
    <!--    查询操作-->
    <select id="findAll" resultType="com.domain.User">
        select * from User
    </select>
    <!--    插入操作-->
    <insert id="add" parameterType="com.domain.User">
        insert into User values (#{id},#{username},#{password})
    </insert>
    <!--    修改数据-->
    <update id="update" parameterType="com.domain.User">
        update User set password = #{password} where username=#{username}
    </update>
    <!--    删除操作-->
    <delete id="delete" parameterType="com.domain.User">
        delete from User where username=#{username}
    </delete>

</mapper>

编写核心文件

<?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">


<!--数据源环境-->
<configuration>
    <!--    指定默认的环境名称-->
    <environments default="development">
        <!--        指定当前环境名称-->
        <environment id="development">
            <!--            事务管理器-->
            <transactionManager type="JDBC"></transactionManager>
            <!--            指定当前数据类型是连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/one"/>
                <property name="username" value="root"/>
                <property name="password" value="admin123"/>
            </dataSource>
        </environment>
    </environments>

    <!--    加载映射文件-->
    <mappers>
        <mapper resource="com/mapper/UserMapper.xml"></mapper>
    </mappers>

</configuration>

编写接口UserMapper

package com.dao;

import com.domain.User;

import java.util.List;

public interface UserMapper {

     List<User> findAll();

}

测试

 @Test
    public void test2() throws IOException {
        //        加载核心配置文件
        InputStream resource = Resources.getResourceAsStream("sqlMapConfig.xml");
//        获得sqlSession工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resource);
//        获得SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
//        获得Mybatis框架生成的UserMapper接口实现类
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> list = userMapper.findAll();
        System.out.println(list);
//        释放资源
        sqlSession.close();
    }