Mybatis二级缓存知识汇总

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1.底层实现原理

2.核心源码

// 读取
TransactionalCacheManager.getTransactionalCache(cache).getObject(key);
        a、getTransactionalCache
        txCache = new TransactionalCache(cache);
            this.delegate = delegate; //对应的二级缓存对象
           this.clearOnCommit = false;//是否在commit时清除二级缓存的标记
           this.entriesToAddOnCommit = new HashMap();//需要在commit时提交到二级缓存的数据
           this.entriesMissedInCache = new HashSet();//缓存未命中的数据，事务commit时，也会放入二级缓存
                                 this.transactionalCaches.put(cache, txCache);

       b、getObject
       delegate.getObject(key);//调用真实缓存读取key对应的值

读取一级缓存或数据库后
CachingExecutor.his.tcm.putObject(cache, key, list);
  TransactionalCacheManager.getTransactionalCache(cache).putObject(key, value);
  TransactionalCacheManager.entriesToAddOnCommit.put(key, object);//先临时存放

sqlSession.close();/ sqlSession.commit();

CachingExecutor.tcm.commit();
Iterator i$ = CachingExecutor.transactionalCaches.values().iterator();
        while(i$.hasNext()) {
            TransactionalCache txCache = (TransactionalCache)i$.next();
            txCache.commit();
            {
               TransactionalCache.flushPendingEntries();
                TransactionalCache.reset();
            }
        }

//TransactionalCache.flushPendingEntries()的实现
将临时存放的数据写入到二级缓存中
    private void flushPendingEntries() {
        Iterator i$ = this.entriesToAddOnCommit.entrySet().iterator();

        while(i$.hasNext()) {
            Entry<Object, Object> entry = (Entry)i$.next();
            this.delegate.putObject(entry.getKey(), entry.getValue());
        }

        i$ = this.entriesMissedInCache.iterator();

        while(i$.hasNext()) {
            Object entry = i$.next();
            if (!this.entriesToAddOnCommit.containsKey(entry)) {
                this.delegate.putObject(entry, (Object)null);
            }
        }
    }

//TransactionalCache.reset();
重置临时存放的数据 
private void reset() {
        this.clearOnCommit = false;
        this.entriesToAddOnCommit.clear();
        this.entriesMissedInCache.clear();
    }

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