3-1 MyBatis 소개, 설정

1. MyBatis란?

SQL Mapping Framework - Easy & Simple
자바 코드로부터 SQL문을 분리해서 관리.
매개변수 설정과 쿼리 결과를 읽어오는 코드를 제거.
작성할 코드가 줄어서 생산성 향상 & 유지 보수 편리.

//이전의 방법
//sql, java가 한 소스코드에 섞여있음.
public int insertUser(User user) {
	int rowCnt = FAIL;
	
	Connection conn = null;
	PreparedStatement pstmt = null;
	
	String sql = "insert into user_info values(?,?,?,?,?,?,new Date())";

	try {
		conn = ds.getConnection();
		pstmt = conn.prepareStatement(sql);
		pstmt.setString(1, user.getId());
		pstmt.setString(2, user.getPwd());
		pstmt.setString(3, user.getName());
		pstmt.setString(4, user.getEmail());
		pstmt.setString(5, new java.sql.Date(user.getBirth.getTime()));
		pstmt.setString(6, user.getSns());
		
		return pstmt.executeUpdate();
	} catch(SQLException e) {
		e.printStrackTrace();
		return FAIL;
	} finally {
		close(pstmt, conn);
	}
}	

//새로운 방법
//XML문서에 SQL만 따로 떼어 냄.
<?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.fastcampus.ch4.dao.UserMapper">
	<insert id="insert" parameterType="com.fastcampus.ch4.domain.UserDto>
		INSERT INTO user_info
		VALUES ( #{id}, #{pwd}, #{name}, #{email}, #{birth}, #{sns}, now());
	</insert>

//새로운 자바코드
@Repository
public class UserDaoImpl implements UserDao {
	@Autowired
	private SqlSession session;
	private static String namespace = "com.fastcampus.ch4.dao.UserMapper.";
	
	@Override
	public int insert(User user) {
		return session.insert(namespace+"insert", user);
	}

2. SqlSessionFactoryBean, SqlSessionTemplate

(1)mybatis가 제공하는 인터페이스
SqlSessionFactory - SqlSession을 생성해서 제공.
SqlSession - SQL명령을 수행하는데 필요한 메서드 제공.

(2)mybatis-spring이 제공. 인터페이스를 구현한 것.
SqlSessionFactoryBean

• SqlSessionFactory를 Spring에서 사용하기 위한 빈
  SqlSessionTemplate
• SQL명령을 수행하는데 필요한 메서드 제공. thread-safe

//root-context.xml
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
	<property name="dataSource" ref="dataSource"/>
	<property name="configLocation" value="classpath:mybatis-config.xml"/>
	<property name="mapperLocations" value="classpath:mapper/*Mapper.xml"/>
</bean>

<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
	<constructor-arg ref="sqlSessionFactory"/>
</bean>

3. SqlSession의 메서드

insert()
delete()
update()
selectOne()
selectList()
selectMap()

4. Mapper XML의 작성

<!-- boardMapper.xml -->
<mapper namespace="com.fastcampus.ch4.dao.BoardMapper">
	<select id="now" resultType="string">
		SELECT now()
	</select>
	
	<select id="count" resultType="int">
		SELECT count(*) from board
	</select>

	<insert id="insert" parameterType="com.fastcampus.ch4.domain.BoardDto">
		INSERT INTO board (title, content, writer)
		VALUES (#{title}, #{content}, #{writer})
	</insert>
	
	<select id="select" parameterType"int"
						resultType="com.fastcampus.ch4.domain.BoardDto">
		SELECT bno, title, content, writer, view_cnt, commnet_cnt, reg_date
		FROM board
		WHERE bno = #{bno}
	</select>

public class BoardDaoImpl implements BoardDao {
	@Autowired
	private SqlSession session;
	private static String namespace 
		= "com.fastcampus.ch4.dao.BoardMapper.";
		
	public String getServerTime() throws Exception {
		return session.selectOne(namespace+"now");
	}
	public int count() throws Exception {
		return session.selectOne(namespace+"count");
	}
	public int insert(BoardDto dto) throws Exception {
		return session.insert(namespace+"insert", dto);
	}
	public BoardDto select(Integer bno) throws Exception {
		return session.selectOne(namespcae+"select", bno);
	}

5. <typeAliases>로 이름 짧게 하기

<typeAliases>
	<typeAlias alias="BoardDto" type="com.fastcampus.ch4.domain.BoardDto"/>
</typeAliases>