MyBatis中自定义二级缓存（使用Redis做缓存）

我不是女神ヾ 2022-05-22 13:35 234阅读 0赞

在MyBatis中，默认的二级缓存Cache实现是PerpetualCache，而通常，这种方式满足不了分布式集群的项目，这时候，我们可以借助一些第三方服务来做缓存，比如Redis，下面，来尝试下用Redis做MyBatis的二级缓存

### 开启二级缓存 ###

![这里写图片描述][70]

### 实现自己的cache ###

package top.yuyufeng.learn.mybatis.cache;
    
    import org.apache.ibatis.cache.Cache;
    import org.springframework.data.redis.core.RedisTemplate;
    import org.springframework.data.redis.core.ValueOperations;
    
    import java.util.concurrent.TimeUnit;
    import java.util.concurrent.locks.ReadWriteLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock;
    
    /**
     * @author yuyufeng
     * @date 2018/6/25.
     */
    public class RedisCache implements Cache {
    
        private final String id;
    
        private static ValueOperations<String, Object> valueOs;
    
        private static RedisTemplate<String, String> template;
    
    
        public static void setValueOs(ValueOperations<String, Object> valueOs) {
            RedisCache.valueOs = valueOs;
        }
    
        public static void setTemplate(RedisTemplate<String, String> template) {
            RedisCache.template = template;
        }
    
        private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    
    
        public RedisCache(String id) {
            if (id == null) {
                throw new IllegalArgumentException("Cache instances require an ID");
            }
            this.id = id;
        }
    
        @Override
        public String getId() {
            return this.id;
        }
    
        @Override
        public void putObject(Object key, Object value) {
            valueOs.set(key.toString(), value, 10, TimeUnit.MINUTES);
        }
    
        @Override
        public Object getObject(Object key) {
            return valueOs.get(key.toString());
        }
    
        @Override
        public Object removeObject(Object key) {
            valueOs.set(key.toString(), "", 0, TimeUnit.MINUTES);
            return key;
        }
    
        @Override
        public void clear() {
            template.getConnectionFactory().getConnection().flushDb();
        }
    
        @Override
        public int getSize() {
            return template.getConnectionFactory().getConnection().dbSize().intValue();
        }
    
        @Override
        public ReadWriteLock getReadWriteLock() {
            return this.readWriteLock;
        }
    }

> 这里使用到了Spring-data-redis

### mapper文件中使用自定义的cache ###

### 调试 ###

package top.yuyufeng.learn.mybatis.service;
    
    import org.junit.Before;
    import org.junit.Test;
    import org.junit.runner.RunWith;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.data.redis.core.RedisTemplate;
    import org.springframework.data.redis.core.ValueOperations;
    import org.springframework.test.context.ContextConfiguration;
    import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
    import top.yuyufeng.learn.mybatis.cache.RedisCache;
    import top.yuyufeng.learn.mybatis.entity.Blog;
    
    import javax.annotation.Resource;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    
    /**
     * @author yuyufeng
     * @date 2018/6/13.
     */
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration({"classpath:spring/spring-redis.xml","classpath:spring/spring-service.xml"})
    public class CacheTest {
    
    
        @Resource(name="redisTemplate")
        private ValueOperations<String, Object> valueOs;
    
        @Autowired
        private RedisTemplate<String, String> template;
    
        @Autowired
        private BlogService blogService;
    
        @Before
        public void testBefore(){
            RedisCache.setTemplate(this.template);
            RedisCache.setValueOs(this.valueOs);
        }
    
        @Test
        public void selectAll() throws Exception {
            List<Blog> list =  blogService.selectAll();
            for (Blog blog : list) {
                System.out.println(blog);
            }
    
            List<Blog> list2 =  blogService.selectAll();
            for (Blog blog : list2) {
                System.out.println(blog);
            }
        }
    
    }

> …  
> Cache Hit Ratio \[top.yuyufeng.learn.mybatis.mapper.BlogMapper\]: 0.5  
> Closing non transactional SqlSession \[org.apache.ibatis.session.defaults.DefaultSqlSession@16073fa8\]  
> Blog\{blogId=1, blogTitle=‘什么是mybatis’, blogContent='MyBatis是支持定制化SQL、存储过程以及高级映射的优秀的持久层框架。  
> ', createTime=Fri May 25 14:28:35 CST 2018\}  
> …

可以看到，我查询了两次，命中率为0.5，缓存已经生效了

[70]: /images/20220522/907c308ed0304ca8a29577b9aed2bc9b.png