一级缓存（默认开始sqlsession级别）和 二级缓存(testTwoCache)

一级缓存（默认开始sqlsession级别）

一级缓存失效的四种情况：
1.不同的sqlsession对应不同的缓存
2.同一个sqlsession但是查询条件不同
3.同一个sqlsession两次查询期间执行了任何一个增删改的操作(testgetEmpByEid3)
4.同一个sqlsession两次查询期间手动清空了缓存

 @Test
    public void getEmpByEmpIdTest(){
        SqlSession sqlSession1 = SqlSessionUtil.getSqlSession();
        CacheMapper mapper1 = sqlSession1.getMapper(CacheMapper.class);
        //此处用的是同一个Sqlsession
        Emp emp1 = mapper1.getEmpByEmpId(1);//第一条emp1
        System.out.println(emp1);
        Emp emp2 = mapper1.getEmpByEmpId(1);//第二条emp2
        System.out.println(emp2);
    }

一级缓存失效情况

@Test
    public void testgetEmpByEid2(){
        SqlSession sqlsession1 = SQLsession.getSqlsession();
        CacheMapper mapper1 = sqlsession1.getMapper(CacheMapper.class);
        Emp empByEid1 = mapper1.getEmpByEid(1);
        System.out.println(empByEid1);
        SqlSession sqlsession2 = SQLsession.getSqlsession();
        CacheMapper mapper2 = sqlsession2.getMapper(CacheMapper.class);
        Emp empByEid2 = mapper2.getEmpByEid(1);
        System.out.println(empByEid2);
    }

@Test
    public void testgetEmpByEid3(){
        SqlSession sqlsession = SQLsession.getSqlsession();
        CacheMapper mapper = sqlsession.getMapper(CacheMapper.class);
        Emp empByEid1 = mapper.getEmpByEid(1);
        System.out.println(empByEid1);
        mapper.insertEmp(new Emp(null,"sdd",12,"1","1",null));
        Emp empByEid2 = mapper.getEmpByEid(1);
        System.out.println(empByEid2);
    }

@Test
    public void testTwoCache(){
        //不能使用工具类的形式创建SQLsession
        try {
           InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
            SqlSessionFactory builder = new SqlSessionFactoryBuilder().build(in);
            SqlSession sqlSession1 = builder.openSession(true);
            CacheMapper mapper1 = sqlSession1.getMapper(CacheMapper.class);
            System.out.println(mapper1.getEmpByEid(1));
            sqlSession1.close();
            SqlSession sqlSession2 = builder.openSession(true);
            CacheMapper mapper2 = sqlSession2.getMapper(CacheMapper.class);
            System.out.println(mapper2.getEmpByEid(1));
            sqlSession2.close();
        } catch (IOException e) {
            e.printStackTrace();
        }


    }

二级缓存(testTwoCache)

1.在核心配置文件中设置全局配置属性cacheEnabled="ture"，默认为ture不需要设置
2.在映射文件中配置标签
3.二级缓存必须在sqlSession关闭或提交后有效
4.查询的数据所转换的实体类类型必须实现序列化的接口(implements Serializable )
二级缓存失效的情况：
两次查询中间执行了任意的增删改查，会使一级缓存和二级缓存同时失效