SqlSession session = sqlSessionFactory.openSession();
try {
  // do work
} finally {
  session.close();
}

<?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="user">
 <!-- 根据id获取用户信息 -->
 <select id="findUserById" parameterType="int" resultType="user">
  select * from user where id = #{id}
 </select>
 <!-- 根据username模糊查询用户信息 -->
 <select id="findUserByName" parameterType="java.lang.String" resultType="com.luchao.mybatis.first.po.User">
  select * from user where username like '%${value}%'
 </select>
 <!-- 添加用户信息 -->
 <insert id="insertUser" parameterType="com.luchao.mybatis.first.po.User">
  <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
   select LAST_INSERT_ID()
  </selectKey>
  insert into user(username,birthday,sex,address) value (#{username},#{birthday},#{sex},#{address});
 </insert>
 <!-- 根据id删除用户信息 -->
 <delete id="deleteUser" parameterType="int">
  delete from user where id=#{id}
 </delete>
 <!-- 修改用户信息 -->
 <update id="updateUser" parameterType="com.luchao.mybatis.first.po.User">
  update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
  where id=#{id}
 </update>
</mapper>

public interface UserDao {
 //根据ID查询用户信息
 public User findUserById(int id) throws Exception;
 //添加用户信息
 public void insertUser(User user) throws Exception;
 //删除用户信息
 public void deleteUser(int id) throws Exception;
}

public class UserDaoImpl implements UserDao{
 
 // 需要向dao实现类中注入SqlSessionFactory
 // 这里通过构造方法注入
 private SqlSessionFactory sqlSessionFactory;
 
 public UserDaoImpl(SqlSessionFactory sqlSessionFactory) {
  super();
  this.sqlSessionFactory = sqlSessionFactory;
 }
 @Override
 public void deleteUser(int id) throws Exception {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  //执行删除操作
  sqlSession.insert("user.deleteUser", id);
  // 提交事务
  sqlSession.commit();
  // 释放资源
  sqlSession.close();
 }
 @Override
 public User findUserById(int id) throws Exception {
  SqlSession sqlSession = sqlSessionFactory.openSession();//获取sqlSession
  User user = sqlSession.selectOne("user.findUserById", id);
  sqlSession.close();//关闭资源
  return user;
 }
 @Override
 public void insertUser(User user) throws Exception {
  SqlSession sqlSession = sqlSessionFactory.openSession();
  //执行插入操作
  sqlSession.insert("user.insertUser", user);
  // 提交事务
  sqlSession.commit();
  // 释放资源
  sqlSession.close();
 }
}

public class MyBatis_dao_test {
 private SqlSessionFactory sqlSessionFactory;
 @Before
 public void init() throws IOException{
  //创建sqlSessionFactory
  //MyBatis配置文件
  String resource = "SqlMapConfig.xml";
  //得到配置文件流
  InputStream inputStream = Resources.getResourceAsStream(resource);
  //创建会话工厂，传入MyBatis的配置信息
  sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 }
 @Test
 public void testFindUserById() throws Exception{
  //创建UserDao对象
  UserDao userDao = new UserDaoImpl(sqlSessionFactory);
  //调用UserDao的方法，根据ID查找user
  User user = userDao.findUserById(10);
  //打印客户信息
  System.out.println(user);
 }
}

<?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.luchao.mybatis.first.mapper.UserMapper">
 <!-- 根据id获取用户信息 -->
 <select id="findUserById" parameterType="int" resultType="user">
  select * from user where id = #{id}
 </select>
 <!-- 根据username模糊查询用户信息 -->
 <select id="findUserByName" parameterType="java.lang.String" resultType="com.luchao.mybatis.first.po.User">
  select * from user where username like '%${value}%'
 </select>
 <!-- 添加用户信息 -->
 <insert id="insertUser" parameterType="com.luchao.mybatis.first.po.User">
  <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer">
   select LAST_INSERT_ID()
  </selectKey>
  insert into user(username,birthday,sex,address) value (#{username},#{birthday},#{sex},#{address});
 </insert>
 <!-- 根据id删除用户信息 -->
 <delete id="deleteUser" parameterType="int">
  delete from user where id=#{id}
 </delete>
 <!-- 修改用户信息 -->
 <update id="updateUser" parameterType="com.luchao.mybatis.first.po.User">
  update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address}
  where id=#{id}
 </update>
</mapper>

public interface UserMapper {
 //根据ID查询用户信息
 public User findUserById(int id) throws Exception;
 //添加用户信息
 public void insertUser(User user) throws Exception;
 //删除用户信息
 public void deleteUser(int id) throws Exception;
 //更新用户信息
 public void updateUser(User user) throws Exception;
 //根据用户名模糊查找
 public List<User> findUserByName(String user) throws Exception;
}

 <mappers>
  <mapper resource="mapper/UserMapper.xml"/>
 </mappers>

public class MyBatis_mapper_test {
 private SqlSessionFactory sqlSessionFactory;
 @Before
 public void init() throws IOException{
  //创建sqlSessionFactory
  //MyBatis配置文件
  String resource = "SqlMapConfig.xml";
  //得到配置文件流
  InputStream inputStream = Resources.getResourceAsStream(resource);
  //创建会话工厂，传入MyBatis的配置信息
  sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 }
 @Test
 public void testFindUserById() throws Exception{
  //获取sqlSession对象
  SqlSession sqlSession = sqlSessionFactory.openSession();
  //创建UserMapper对象，MyBatis自动生成mapper代理
  UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
  //调用userMapper的方法
  User user = userMapper.findUserById(10);
  //关闭资源
  sqlSession.close();
  //打印客户信息
  System.out.println(user);
 }
}