一级缓存案例

目的：提高查询效率，减少数据库压力
test：

  //根据gid查询goods
    @Test
    public void testSelGoodsByGid(){
    
    
        GoodsDao mapper = session.getMapper(GoodsDao.class);
        Goods goods = mapper.selGoodsByGid(4);
        System.out.println(goods);
        System.out.println("----------------");
        //再次根据同一个条件查询
        Goods goods1 = mapper.selGoodsByGid(4);
        //不会再次调用sql语句，因为mybatis默认开启了一级缓存
        System.out.println(goods1);
        System.out.println("================");
        //清除缓存
        session.clearCache();
        //再次根据同一个条件查询
        Goods goods2 = mapper.selGoodsByGid(4);
        //需要调用sql语句
        System.out.println(goods2);
    }

log4j：

DEBUG [main] - ==>  Preparing: select * from t_goods WHERE gid = ? 
DEBUG [main] - ==> Parameters: 4(Integer)
DEBUG [main] - <==      Total: 1
Goods{
    
    gid=4, gname='冰箱', gprice=3155.55, gcount=30, gdate=Sat Aug 15 00:00:00 CST 2020}
----------------
Goods{
    
    gid=4, gname='冰箱', gprice=3155.55, gcount=30, gdate=Sat Aug 15 00:00:00 CST 2020}
================
DEBUG [main] - ==>  Preparing: select * from t_goods WHERE gid = ? 
DEBUG [main] - ==> Parameters: 4(Integer)
DEBUG [main] - <==      Total: 1
Goods{
    
    gid=4, gname='冰箱', gprice=3155.55, gcount=30, gdate=Sat Aug 15 00:00:00 CST 2020}