动态代理Dao

假设现在环境已配好，需要使用动态代理的Dao，也被称为mapper

1. 创建接口UserMapper.java

接口和以前一样，正常定义

public interface UserMapper {
    public User getUserById(Integer id);
}

2. 创建UserMapper.xml ，用于编写sql映射

注意：

• 在同一包下创建映射文件
• namespace 为接口的全路径
• id 为接口对应的方法
• 输入、输出参数类型要一致

<?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.UserMapper">
    <select id="getUserById" parameterType="java.lang.Integer" resultType="com.itheima.pojo.User">
        select * from user where id = #{id}
    </select>
</mapper>

3. 在配置文件中 加载映射

<package name="com.itheima.mapper"/>

在映射文件和接口文件 同一包下时，可使用package配置。

4.测试程序

1. 获取session
2. 传入mapper接口类，获取mapper
3. 调用mapper方法

public class Demo1 {
    private SqlSessionFactory factory;
    @Before
    public void setUp() throws IOException {
        String resource = "SqlMapConfig.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        this.factory = new SqlSessionFactoryBuilder().build(inputStream);
    }
    public void run1(){
      SqlSession session = this.factory.openSession();
      UserMapper mapper = session.getMapper(UserMapper.class);
      User user = mapper.getUserById(5);
      System.out.println(user);
      session.commit();
    }