mybatis一级缓存

mybatis一级缓存：在同一个sqlsession中，查询语句相同且查询参数相同，第二次查询时取缓存的数据

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.defaults.DefaultSqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import cn.mgr.user.po.UserPO;

//mybatis一级缓存
public class SessionTest {

public static void main(String[] args)throws Exception{
  ClassPathXmlApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
  DefaultSqlSessionFactory factory = (DefaultSqlSessionFactory)app.getBean("sqlSessionFactory");

  mybatisFirstCache(factory); //一级缓存:必须在同一个会话里

  //mybatisFirstCache2(factory);
  //mybatisFirstCache3(factory);

}

/**
* mybatis一级缓存: 同一个会话里的sql会缓存:
* 查询语句相同且查询参数相同,第二次在同一个会话里取缓存的结果
* @param factory
*/
static void mybatisFirstCache(DefaultSqlSessionFactory factory){
  SqlSession session = factory.openSession();

  String statement = "cn.mgr.user.mapper.UserMapper.findByID";
  UserPO user = new UserPO();
  user.setUserId(100);
  UserPO u = session.selectOne(statement, user);
  System.out.println("第一次查询："+u.getUserName());

  user = new UserPO();
  user.setUserId(100);
  u = session.selectOne(statement, user);
  System.out.println("第二次查询："+u.getUserName());

  session.close();
}

/**
* mybatis一级缓存: 同一个会话里的sql会缓存:
* 查询语句相同且查询参数不同,第二次仍然会查询数据库
* @param factory
*/
static void mybatisFirstCache2(DefaultSqlSessionFactory factory){
  SqlSession session = factory.openSession();

  String statement = "cn.mgr.user.mapper.UserMapper.findByID";
  UserPO user = new UserPO();
  user.setUserId(100);
  UserPO u = session.selectOne(statement, user);
  System.out.println("第一次查询："+u.getUserName());

  user = new UserPO();
  user.setUserId(101);
  u = session.selectOne(statement, user);
  System.out.println("第二次查询："+u.getUserName());

  session.close();
}

/**
* mybatis一级缓存: 不同的会话
* 查询语句相同且查询参数不同,第二次仍然会查询数据库
* @param factory
*/
static void mybatisFirstCache3(DefaultSqlSessionFactory factory){
  SqlSession session = factory.openSession();

  String statement = "cn.mgr.user.mapper.UserMapper.findByID";
  UserPO user = new UserPO();
  user.setUserId(100);
  UserPO u = session.selectOne(statement, user);
  System.out.println("第一次查询："+u.getUserName());
  session.close();

  session = factory.openSession();
  user = new UserPO();
  user.setUserId(100);
  u = session.selectOne(statement, user);
  System.out.println("第二次查询："+u.getUserName());

  session.close();
}
}

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