/**
 * 根据ID查询用户
 *
 * @param id
 * @return
 */
@Select("select * from user where id=#{id}")
User findUserById(Integer id);

@Before
public void before() throws Exception {
    System.out.println("before...");
    InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
    //根据 sqlSessionFactory 产生 session
    sqlSession = sqlSessionFactory.openSession();
    // 这样也是可以的，这样的话后面就不用每次都设置了
    // sqlSession = sqlSessionFactory.openSession(true);
    userMapper = sqlSession.getMapper(IUserMapper.class);
}

@Test
public void testFindUserById() {
    //第一次查询，发出sql语句，并将查询出来的结果放进缓存中
    User user = userMapper.findUserById(1);
    System.out.println(user);

    //第二次查询，由于是同一个sqlSession,会在缓存中查询结果 //如果有，则直接从缓存中取出来，不和数据库进行交互
    User user2 = userMapper.findUserById(1);
    System.out.println(user2);
}