MyBatis的一级缓存

什么是缓存？

把当前查询出来的数据进行记录，下一次查询相同数据时，从缓存中去取，就不会重新访问数据库了

MyBatis的缓存分为一级缓存和二级缓存

一级缓存默认是开启的

缓存只针对查询功能有效

CacheMapper

CacheMapper.xml

测试

package com.baidu.mybatis;
import com.baidu.mybatis.mapper.CacheMapper;
import com.baidu.mybatis.pojo.Emp;
import com.baidu.mybatis.utils.SqlSessionUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
public class CacheMapperTest {

    @Test
    public void testCache() {
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        SqlSession sqlSession2 = SqlSessionUtils.getSqlSession();

        CacheMapper mapper = sqlSession.getMapper(CacheMapper.class);

        Emp emp = mapper.getEmpByEid(1);
        Emp emp2 = mapper.getEmpByEid(1);

        System.out.println("emp = " + emp);
        System.out.println("emp2 = " + emp2);

        System.out.println("--------------------");

        CacheMapper mapper1 = sqlSession.getMapper(CacheMapper.class);
        Emp emp3 = mapper1.getEmpByEid(1);
        Emp emp4 = mapper1.getEmpByEid(1);
        System.out.println("emp3 = " + emp3);
        System.out.println("emp4 = " + emp4);

        System.out.println("------------------------");

        CacheMapper mapper2 = sqlSession2.getMapper(CacheMapper.class);
        Emp emp5 = mapper2.getEmpByEid(1);
        Emp emp6 = mapper2.getEmpByEid(1);
        System.out.println("emp5 = " + emp5);
        System.out.println("emp6 = " + emp6);


    }

}

可以看到不同sqlsession，才会输出sql语句