public Employee getEmpById(Integer id);

	<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee" databaseId="mysql" >

		select * from tbl_employee where id = #{id}

	</select>

	@Test

	public void testFirstLevelCache() throws IOException {

		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

		SqlSession openSession = sqlSessionFactory.openSession();

		try {

			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

			Employee emp01 = mapper.getEmpById(10);

			System.out.println(emp01);

			//

			Employee emp02 = mapper.getEmpById(1-0);

			System.out.println(emp02);

			System.out.println(emp01==emp02);

		}finally {

			openSession.close();

		}

	}

	public Employee getEmpById(Integer id);

	<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee" databaseId="mysql" >

		select * from tbl_employee where id = #{id}

	</select>

	@Test

	public void testFirstLevelCache() throws IOException {

		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

		SqlSession openSession = sqlSessionFactory.openSession();

		try {

			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

			Employee emp01 = mapper.getEmpById(10);

			System.out.println(emp01);

			//1、Sqlsession不同

//			SqlSession openSession2 = sqlSessionFactory.openSession();

//			EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);

//			Employee emp02 = mapper2.getEmpById(10);

			//2、sqlSession相同,查询条件不同

//			Employee emp02 = mapper.getEmpById(3);

//			System.out.println(emp02);

//			System.out.println(emp01==emp02);

			//3、sqlSession相同,两次查询之间执行了增删改操作

//			mapper.addEmp(new Employee(null, "testCache", "cache@cache.com", "1"));

//			System.out.println("数据添加成功");

//			Employee emp02 = mapper.getEmpById(10);

//			System.out.println(emp02);

//			System.out.println(emp01==emp02);

			//4、sqlSession相同，手动清除了一级缓存

			openSession.clearCache();

			Employee emp02 = mapper.getEmpById(10);

			System.out.println(emp02);

			System.out.println(emp01==emp02);

		}finally {

			openSession.close();

		}

	}

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

<mapper namespace="com.atguigu.mybatis.dao.EmployeeMapper">

	<!-- cache:使用二级缓存的namespace -->

	<!-- eviction:缓存的清除策略;LRU|FIFO|SOFT|WEAK -->

		<!-- LRU – 最近最少使用的：移除最长时间不被使用的对象。 -->

		<!-- FIFO – 先进先出：按对象进入缓存的顺序来移除它们。 -->

		<!-- SOFT – 软引用：基于垃圾回收器状态和软引用规则移除对象。 -->

		<!-- WEAK – 弱引用：更积极地基于垃圾收集器状态和弱引用规则移除对象。 -->

	<!-- flushInterval(刷新间隔):缓存多长时间清空一次，默认不清空，可以设置一个毫秒值启用刷新间隔 -->

	<!-- readOnly(只读):属性可以被设置为 true 或 false -->

		<!-- true:只读;mybatis认为所有从缓存中获取数据的操作都是只读操作,不会修改数据; -->

			<!-- 只读的缓存会给所有调用者返回缓存对象的相同实例。 因此这些对象不能被修改。 提供了可观的性能提升-->

		<!-- false:非只读;mybatis觉得获取的数据可能会被修改; -->

			<!-- 可读写的缓存会（通过序列化）返回缓存对象的拷贝。 速度上会慢一些，但是更安全，因此默认值是 false -->

	<!-- size(引用数目):属性可以被设置为任意正整数,要注意欲缓存对象的大小和运行环境中可用的内存资源.默认值是 1024 -->

	<!-- type:属性指定的类必须实现 org.apache.ibatis.cache.Cache 接口.且提供一个接受 String 参数作为 id 的构造器 -->

		<!-- 指定自定义缓存的全类名,实现Cache接口即可 -->

	<!-- <cache eviction="FIFO" flushInterval="60000" readOnly="false" size="1024"></cache> -->

	<cache></cache>

</mapper>

	@Test

	public void testSecondLevelCache() throws IOException {

		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

		SqlSession openSession = sqlSessionFactory.openSession();

		SqlSession openSession2 = sqlSessionFactory.openSession();

		try {

			//1、

			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

			EmployeeMapper mapper2 = openSession2.getMapper(EmployeeMapper.class);

			Employee emp01 = mapper.getEmpById(1);

			System.out.println(emp01);

			openSession.close();

			//第二次查询是从二级缓存中拿到的数据，并没有发送新的sql

			//mapper2.addEmp(new Employee(null, "aaa", "nnn", "0"));

			Employee emp02 = mapper2.getEmpById(1);

			System.out.println(emp02);

			openSession2.close();

		}finally {

		}

	}