mybatis入门学习

首先mybatis有一个总的配置文件，和映射文件,可以在下载的pdf介绍中参考写法

下面演示一个使用mybatis的CUDR操作

总配置文件sqlMapConfig.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>
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql:///mybatis" />
				<property name="username" value="root" />
				<property name="password" value="123" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<!-- 映射文件 -->
		<mapper resource="cn/mybatis/domain/User.xml" />
	</mappers>
</configuration>

映射文件

<?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="cn.mybatis.domain.User"><!-- namespace保证唯一 -->
	<!-- 根据id查询, parameterType参数类型, resultType结果类型-->
	<select id="selectUserById" parameterType="string" resultType="cn.mybatis.domain.User">
		select * from User where id = #{id}
	</select>
	
	<!-- 查询返回为map -->
	<select id="selectUserByIdForMap" parameterType="string" resultType="hashmap">
		select * from User where id = #{id}
	</select>
	
	<!-- 动态sql where可以代替1=1-->
	<select id="selectUserByCondition" parameterType="cn.mybatis.domain.User" resultType="cn.mybatis.domain.User">
		select * from User where
		<where>
			<if test="id != null">
				id = #{id}
			</if>
			<if test="name != null">
				and name = #{name}
			</if>
			<if test="address != null">
				and address = #{address}
			</if>
		</where>
	</select>
	
	<!-- 查询所有 -->
	<select id="selectAllUser" resultType="cn.mybatis.domain.User">
		select * from User
	</select>
	
	<!-- 插入 -->
	<select id="insertUser" parameterType="cn.mybatis.domain.User">
		insert into user (id, name, address) values (#{id}, #{name}, #{address})
	</select>
	
	<!-- 删除 -->
	<select id="deleteUserById" parameterType="string">
		delete from user where id = #{id}
	</select>
	
	<!-- 更新-->
	<select id="updateUserById" parameterType="cn.mybatis.domain.User">
		update user set name = #{name}, address = #{address} where id = #{id}
	</select>
</mapper>

然后是测试类

package cn.mybatis.test;

import java.io.InputStream;
import java.util.List;
import java.util.Map;

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 org.junit.Test;

import cn.mybatis.domain.User;

public class MybatisTest {
	public SqlSession getSession() throws Exception {
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(inputStream);
		SqlSession session = ssf.openSession();
		return session;
	}
	
	/**
	 * 查询User
	 * @throws Exception
	 */
	@Test
	public void selectOne() throws Exception {
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(inputStream);
		SqlSession session = ssf.openSession();
		
		User user = session.selectOne("cn.mybatis.domain.User.selectUserById", "001");
		System.out.println(user);
	}
	
	/**
	 * 查询返回map类型
	 * @throws Exception
	 */
	@Test
	public void selectUserForMap() throws Exception {
		SqlSession session = getSession();
		
		Map<String, String> map = session.selectOne("cn.mybatis.domain.User.selectUserByIdForMap", "001");
		System.out.println(map);
	}
	
	//删除
	@Test
	public void deleteUserById() throws Exception {
		SqlSession session = getSession();
		session.delete("cn.mybatis.domain.User.deleteUserById", "002");
		session.commit();
	}
	
	//更新
	@Test
	public void updateUserById() throws Exception {
		SqlSession session = getSession();
		User user = new User();
		user.setId("002");
		user.setName("zhaodaxia");
		user.setAddress("shanghai");
		session.delete("cn.mybatis.domain.User.updateUserById", user);
		session.commit();
	}
	//查询所有
	@Test
	public void selectList() throws Exception {
		String resource = "sqlMapConfig.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		SqlSessionFactory ssf = new SqlSessionFactoryBuilder().build(inputStream);
		SqlSession session = ssf.openSession();
		
		List<User> userList = session.selectList("cn.mybatis.domain.User.selectAllUser");
		for (User user : userList) {
			System.out.println(user);
		}
	}
	//插入
	@Test
	public void insertUser() throws Exception {
		SqlSession session = getSession();
		User user = new User();
		user.setId("002");
		user.setName("xiaozhao");
		user.setAddress("shanghai");
		//i影响的数据库条数
		int i = session.insert("cn.mybatis.domain.User.insertUser", user);
		//影响数据库需要提交事务
		session.commit();
		System.out.println(i);
	}
	
	//动态sql
	@Test
	public void selectUserByCondition() throws Exception {
		SqlSession session = getSession();
		User user = new User();
		user.setName("zhaodaxia");
		List<User> userList = session.selectList("cn.mybatis.domain.User.selectUserByCondition", user);
		for (User userResult : userList) {
			System.out.println(userResult);
		}
	}
}

当实体和数据库表明字段不一致时，可以在sql语句中使用别名，