ehcache memcache 区别_ehcache缓存原理_ehcache使用(13)

说明：

1、代码的逻辑其实很简单，我们看一下compoundStore这个类，实际上我们缓存的数据最终都是要到这个类里面进行存储的。

2、代码里面使用了putObserver观察者对象主要是用来做计数统计任务用的。

看一下compoundStore类的继承如下：

通过图中可以看到所有的存储类都实现Store接口类，大概有以下几种存储方式：

1、集群方式：ClusteredStore

2、缓存方式：CacheStore

3、内存方式：MemoryStore

4、磁盘方式：DiskStore

我们以DiskStore为例深入讲解磁盘的部分源码分析。

writeLock().lock();
        try {
            // ensure capacity
            if (count + 1 > threshold) {
                rehash();
            }
            HashEntry[] tab = table;
            int index = hash & (tab.length - 1);
            HashEntry first = tab[index];
            HashEntry e = first;
            while (e != null && (e.hash != hash || !key.equals(e.key))) {
                e = e.next;
            }

            Element oldElement;
            if (e != null) {
                DiskSubstitute onDiskSubstitute = e.element;
                if (!onlyIfAbsent) {
                    e.element = encoded;
                    installed = true;
                    oldElement = decode(onDiskSubstitute);

                    free(onDiskSubstitute);
                    final long existingHeapSize = onHeapPoolAccessor.delete(onDiskSubstitute.onHeapSize);
                    LOG.debug("put updated, deleted {} on heap", existingHeapSize);

                    if (onDiskSubstitute instanceof DiskStorageFactory.DiskMarker) {
                        final long existingDiskSize = onDiskPoolAccessor.delete(((DiskStorageFactory.DiskMarker) onDiskSubstitute).getSize());
                        LOG.debug("put updated, deleted {} on disk", existingDiskSize);
                    }
                    e.faulted.set(faulted);
                    cacheEventNotificationService.notifyElementUpdatedOrdered(oldElement, element);
                } else {
                    oldElement = decode(onDiskSubstitute);

                    free(encoded);
                    final long outgoingHeapSize = onHeapPoolAccessor.delete(encoded.onHeapSize);
                    LOG.debug("put if absent failed, deleted {} on heap", outgoingHeapSize);
                }
            } else {
                oldElement = null;
                ++modCount;
                tab[index] = new HashEntry(key, hash, first, encoded, new AtomicBoolean(faulted));
                installed = true;
                // write-volatile
                count = count + 1;
                cacheEventNotificationService.notifyElementPutOrdered(element);
            }
            return oldElement;

        } finally {
            writeLock().unlock();

            if (installed) {
                encoded.installed();
            }
        }

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