MyBatis xml綁定interface的設定

MyBatis可以透過在xml中撰寫SQL，並將xml綁定到一個給程式呼叫的interface，如此程式就可以透過呼叫interface的方法來執行xml中對應的SQL，而綁定xml和interface的設定是在mapper(xml)檔的<mapper namespace>。

<mapper namespace="idv.matt.dao.mapper.UserMapper">

例如有個給程式呼叫的interface UserMapper.java如下，對應到UserMapper.xml。

package idv.matt.dao.mapper;

public interface UserMapper {
 
  User selectUser(String id);

}

綁定的UserMapper.xml如下

<?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="idv.matt.dao.mapper.UserMapper">
  <select id="selectUser" parameterType="String" resultType="hashmap">
    SELECT USER_ID, USER_NAME, USER_AGE, USER_EMAIL 
    FROM USER_PROFILE
    WHERE USER_ID = #{id}
  </select>
</mapper>

所以在程式中要取得使用者資料，可以使用下面來呼叫。

String resource = "resources/mybatis-config.xml"; // mybatis配置檔的路徑
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = 
  new SqlSessionFactoryBuilder().build(inputStream); // 取得SessionFactory

SqlSession session = sqlSessionFactory.openSession(); // 開啟一個Session
try {
  UserMapper mapper = session.getMapper(UserMapper.class); // 取得Mapper實例
  User user = mapper.selectUser("A001");
} finally {
  session.close();
}