mybatis一级缓存、二级缓存以及缓存被刷新的情况

╰+攻爆jí腚メ 2021-11-17 08:18 527阅读 0赞

**一级缓存：是session级别的缓存，默认开启，在一个session没有关闭的情况下执行两次相同的查询，第二次查询会从缓存中获取数据。**

**一级缓存被刷新的情况：在两次相同查询之间插入其他操作（如：增删改），session的缓存会被清空，执行下一次查询会重新执行sql语句。**

**二级缓存：默认关闭，如果在不同的session范围内，执行相同的数据查询，那么每次查询都是独立地从数据库查询。**

**二级缓存被刷新的情况：开启了二级缓存的情况下，和一级缓存一样，在两次相同查询之间插入其他操作（如：增删改），二级缓存区会被清空，执行下一次查询会重新执行sql语句。**

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## 一级缓存 ##

**测试类：**

//一级缓存
    	@Test
    	public void delectBlogOne() { 
    		SqlSession session = MyBatisUtil.getSqlSession();
    		BlogMapper blogMapper = session.getMapper(BlogMapper.class);
    		
    		Blog blog1=blogMapper.selectBlog(38);
    		System.out.println("查询成功");
    		
    		
    		Blog blog2=blogMapper.selectBlog(38);
    		System.out.println("查询成功");
    
    		//关闭session
    		session.close();
    
    		System.out.println("session关闭");
    
    	}

**控制台打印语句：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70]

--------------------

## 一级缓存被刷新的情况 ##

**测试类:**

@Test
    	public void delectBlogOne1() { 
    		SqlSession session = MyBatisUtil.getSqlSession();
    		BlogMapper blogMapper = session.getMapper(BlogMapper.class);
    		
    		Blog blog1=blogMapper.selectBlog(38);
    		System.out.println("查询成功");
    		
    		blog1.setFeatured(false);
    		blogMapper.updateBlog(blog1);
    		
    		
    		Blog blog2=blogMapper.selectBlog(38);
    		System.out.println("查询成功");
    		
    		session.commit();
    		session.close();
    
    		System.out.println("session关闭");
    
    	}

**控制台打印语句：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 1]

--------------------

## 二级缓存 ##

**开启二级缓存：**  
**一、在xml文件中设置cache**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 2]  
**二、实体类中实现序列化接口**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 3]

**测试类:**

//二级缓存
    	@Test
    	public void delectBlogTwo() { 
    		SqlSession session1 = MyBatisUtil.getSqlSession();
    		BlogMapper blogMapper1 = session1.getMapper(BlogMapper.class);
    		
    		Blog blog1=blogMapper1.selectBlog(38);
    		System.out.println("查询成功");
    		session1.close();
    		
    		SqlSession session2 = MyBatisUtil.getSqlSession();
    		BlogMapper blogMapper2 = session2.getMapper(BlogMapper.class);
    		
    		Blog blog2=blogMapper2.selectBlog(38);
    		System.out.println("查询成功");
    		session2.close();
    
    		//System.out.println("session关闭");
    
    	}

**控制台打印语句：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 4]

--------------------

## 二级缓存被刷新的情况 ##

**测试类:**

@Test
    	public void delectBlogTwo1() { 
    		SqlSession session1 = MyBatisUtil.getSqlSession();
    		BlogMapper blogMapper1 = session1.getMapper(BlogMapper.class);
    		
    		Blog blog1=blogMapper1.selectBlog(38);
    		System.out.println("查询成功");
    		
    		blog1.setFeatured(true);
    		blogMapper1.updateBlog(blog1);
    		session1.commit();
    		session1.close();
    		
    		SqlSession session2 = MyBatisUtil.getSqlSession();
    		BlogMapper blogMapper2 = session2.getMapper(BlogMapper.class);
    		
    		Blog blog2=blogMapper2.selectBlog(38);
    		System.out.println("查询成功");
    		session2.close();
    
    		//System.out.println("session关闭");
    
    	}

**控制台打印语句：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 5]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 1]: /images/20211116/e7b4a83d28664c3f9e1d63322e082e3d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 2]: /images/20211116/f052a76d82474174abcb39a17732ade0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 3]: /images/20211116/68437820800648549526f6acb5e5b7a3.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 4]: /images/20211116/d7bfe50bbd3d4705b61e500c26532810.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMDgzMDA5_size_16_color_FFFFFF_t_70 5]: /images/20211116/fe0bb6bebfb042a3ab2bfb9449533b21.png