<setting name="cacheEnabled" value="true"/> 

<select useCache="false"></select>

<insert flushCache="false"></insert>

SqlSession session1 = factory.openSession();
   SqlSession session2 = factory.openSession();
   SqlSession session3 = factory.openSession();
   UserMapper mapper1 = session1.getMapper(UserMapper.class);
   UserMapper mapper2 = session2.getMapper(UserMapper.class);
   UserMapper mapper3 = session3.getMapper(UserMapper.class);
   //第一次请求,查询id为1的用户
   User user1 = mapper1.findUserById(1);
   System.out.println(user1);
   //close 将数据写入二级缓存
   session1.close();
   //清空二级缓存,UserMapper下的
   user1.setUsername("mmm");
   mapper3.updateUser(user1);
   session3.commit();
   //第二次查询会从缓存中找
   User user2 = mapper2.findUserById(1);
   System.out.println(user2);
   session2.close();