真正的mybatis_redis二级缓存

Posted 2020-08-09

 

网上流传的代码缓存失效存在严重问题。

思路....以后再细说

目前的方案还不够完美，失效力度控制不够细。

主要代码

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.Properties;
import java.util.Set;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
 
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.ibatis.cache.Cache;
import org.apache.log4j.Logger;


import redis.clients.jedis.Jedis;

 
/*
 * 使用第三方缓存服务器，处理二级缓存
 * zuimao
 */
public class RedisCache implements Cache {
     
    private static final Logger logger = Logger.getLogger(RedisCache.class);
     
    /** The ReadWriteLock. */
    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
 
    private final String COMMON_CACHE_KEY = "MYBATIS:";
    private static final String UTF_8 = "utf-8";
  
    /**
     * 按照一定规则标识key
     */
    private String getKey(Object key) {
        StringBuilder accum = new StringBuilder();
        accum.append(COMMON_CACHE_KEY);
        accum.append(this.id).append(":");
        accum.append(DigestUtils.md5Hex(String.valueOf(key)));
        return accum.toString();
    }
  
    /**
     * redis key规则前缀
     */
    private String getKeys() {
        return COMMON_CACHE_KEY + this.id + ":*";
    }
 
    private String id; 
 
    public RedisCache() {
    }
 
    public RedisCache(final String id) {
        if (id == null) {
            throw new IllegalArgumentException("必须传入ID");
        }
        logger.debug("MybatisRedisCache:id=" + id);
        this.id = id;
    }
 
    @Override
    public String getId() {
        return this.id;
    }
 
    @Override
    public int getSize() {
        Jedis jedis = null;
        int result = 0;
        try {
            jedis = RedisStandAloneUtil.getJedisPool().getResource();
            Set<byte[]> keys = jedis.keys(getKeys().getBytes(UTF_8));
            if (null != keys && !keys.isEmpty()) {
                result = keys.size();
            }
            logger.debug(this.id+"---->>>>总缓存数:" + result);
        } catch (Exception e) {
        	 logger.error(e.getMessage(), e);
        } finally {
        	if (jedis != null) {
                jedis.close();
            }
            
        }
        return result;
    }
 
    @Override
    public void putObject(Object key, Object value) {
        Jedis jedis = null;
        try {
            jedis = RedisStandAloneUtil.getJedisPool().getResource();             
            byte[] keys = getKey(key).getBytes(UTF_8);
            jedis.set(keys, SerializeUtil.serialize(value));
            logger.debug("添加缓存--------"+this.id);
            //getSize();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
 
    }
 
    @Override
    public Object getObject(Object key) {
        Jedis jedis = null;
        Object value = null;
        try {
        	jedis = RedisStandAloneUtil.getJedisPool().getResource();
            value = SerializeUtil.unserialize(jedis.get(getKey(key).getBytes(UTF_8)));
            logger.debug("从缓存中获取-----"+this.id);
            //getSize();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
        return value;
    }
 
    @Override
    public Object removeObject(Object key) {
        Jedis jedis = null;
        Object value = null;
        try {
        	jedis = RedisStandAloneUtil.getJedisPool().getResource();
            value = jedis.del(getKey(key).getBytes(UTF_8));
            logger.debug("LRU算法从缓存中移除-----"+this.id);
            //getSize();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
        return value;
    }
 
    @Override
    public void clear() {
        Jedis jedis = null;
        try {
        	jedis = RedisStandAloneUtil.getJedisPool().getResource();
            Set<byte[]> keys = jedis.keys(getKeys().getBytes(UTF_8));
            logger.debug("出现CUD操作，清空对应Mapper缓存======>"+keys.size());
            for (byte[] key : keys) {
                jedis.del(key);
            }
            //下面是网上流传的方法，极大的降低系统性能，没起到加入缓存应有的作用，这是不可取的。
            //jedis.flushDB();
            //jedis.flushAll();
        } catch (Exception e) {
            logger.error(e.getMessage(), e);
        } finally {
            if (jedis != null) {
                jedis.close();
            }
        }
    }
 
    @Override
    public ReadWriteLock getReadWriteLock() {
        return readWriteLock;
    }
     
}