09_一级缓存与二级缓存

CREATE TABLE c_user(
	id INT PRIMARY KEY AUTO_INCREMENT, 
	NAME VARCHAR(20), 
	age INT
);
INSERT INTO c_user(NAME, age) VALUES(‘Tom‘, 12);
INSERT INTO c_user(NAME, age) VALUES(‘Jack‘, 11);

public class CUser implements Serializable{
	private int id;
	private String name;
	private int age;
｝

<select id="getUser" parameterType="int" resultType="CUser">
    select * from c_user where id=#{id}
</select>
<update id="updateUser" parameterType="CUser">
    update c_user set name=#{name}, age=#{age} where id=#{id}
</update>

@Test
	public void testCacheOne1() {
		SqlSessionFactory factory = MybatisUtils.getFactory();
		SqlSession session = factory.openSession();
		String statement = "cn.imentors.mybatis.test9.userMapper.getUser";
		CUser user = session.selectOne(statement, 1);
		System.out.println(user);
		//默认一级缓冲是开启的
		user = session.selectOne(statement, 1);
		System.out.println(user);
		System.out.println("----------------");
		session.close();
	}

@Test
	public void testCacheOne2() {
		SqlSessionFactory factory = MybatisUtils.getFactory();
		SqlSession session = factory.openSession();
		String statement = "cn.imentors.mybatis.test9.userMapper.getUser";
		CUser user = session.selectOne(statement, 1);
		System.out.println(user);
		//执行了session.clearCache(),清空缓存
		session.clearCache();
		user = session.selectOne(statement, 1);
		System.out.println(user);
		System.out.println("----------------");
		session.close();
	}

@Test
	public void testCacheOne4() {
		SqlSessionFactory factory = MybatisUtils.getFactory();
		SqlSession session = factory.openSession();
		String statement = "cn.imentors.mybatis.test9.userMapper.getUser";
		CUser user = session.selectOne(statement, 1);
		System.out.println(user);
		//不是同一个Session对象
		session.close();
		session = factory.openSession();
		user = session.selectOne(statement, 1);
		System.out.println(user);
		System.out.println("----------------");
		session.close();
	}

<mapper namespace="cn.imentors.mybatis.test9.userMapper">
	<cache/>

• 为什么在userMapper.xml添加呢，因为二级缓存是以namespace为单位，也就是说，二级缓存的作用域是实体SQL对应的xml，二级缓存是映射文件级的
  

@Test
	public void testCacheTwo() {
		SqlSessionFactory factory = MybatisUtils.getFactory();
		SqlSession session1 = factory.openSession();
		SqlSession session2 = factory.openSession();
		
		String statement = "cn.imentors.mybatis.test9.userMapper.getUser";
		CUser user = session1.selectOne(statement, 1);
		session1.commit();
		System.out.println(user);
		
		user = session2.selectOne(statement, 1);
		session2.commit();
		System.out.println(user);
	}

<cache 
eviction="FIFO"  //回收策略为先进先出
flushInterval="60000" //自动刷新时间60s
size="512" //最多缓存512个引用对象
readOnly="true"/> //只读