spring緩存集成memcache

spring3.1.0開始支持註解方式的緩存實現，非常方便，不過它目前只支持java內置的ConcurrentMap和ehcache這兩種緩存方式，因爲項目用到memcache，就想把memcache集成到spring內置的緩存中，使memcache也能用註解方式來調用。於是參考ehcache的集成方式，把memcache集成到項目中。spring把所有緩存都抽象爲一個cache，相當於一個緩存集合，即spring緩存註解@Cacheable(value="xxx")中xxx對應的結果集合。首先我們要實現Cache這個接口，memcache的java客戶端我們用的是com.danga.MemCached.MemCachedClient這個，代碼如下：

public class MemcacheCache implements Cache {

  private MemCachedClient client;
  private String name;

  public MemcacheCache(){

  }

  public MemcacheCache(String name,MemCachedClient client) {
    Assert.notNull(client, "Memcache client must not be null");
    // TODO validate memcache "alive"
    this.client = client;
    this.name = name;
  }

  @Override
  @Cacheable(value="xxxx")
  public String getName() {
    return this.name;
  }

  @Override
  public Object getNativeCache() {
    return this.client;
  }

  @Override
  public ValueWrapper get(Object key) {
    Object value = this.client.get(objectToString(key));
    return (value != null ? new SimpleValueWrapper(value) : null);
  }

  @Override
  public void put(Object key, Object value) {
    this.client.set(objectToString(key), value);

  }

  @Override
  public void evict(Object key) {
    this.client.delete(objectToString(key));

  }

  @Override
  public void clear() {
    // TODO delete all data
  }

  private static String objectToString(Object object) {
    if (object == null) {
      return null;
    } else if (object instanceof String) {
      return (String) object;
    } else {
      return object.toString();
    }
  }

  public void setClient(MemCachedClient client){
    this.client = client;
  }

  public MemCachedClient getClient() {
    return client;
  }

  public void setName(String name) {
    this.name = name;
  }

}

然後是要擴展AbstractCacheManager這個緩存管理抽象類，它主要負責生成和讀取Cache，代碼如下：

public class MemcacheCacheManager extends AbstractCacheManager {

  private Collection<Cache> caches;
  private MemCachedClient client = null;

  public MemcacheCacheManager() {

  }

  public MemcacheCacheManager(MemCachedClient client){
    setClient(client);
  }

  @Override
  protected Collection<? extends Cache> loadCaches() {
    return this.caches;
  }

  public void setCaches(Collection<Cache> caches) {
    this.caches = caches;
  }

  public void setClient(MemCachedClient client) {
    this.client = client;
    updateCaches();
  }

  public Cache getCache(String name){
    checkState();

    Cache cache = super.getCache(name);
    if(cache == null){
      cache = new MemcacheCache(name, client);
      addCache(cache);
    }
    return cache;
  }

  private void checkState() {
    if(client == null){
      throw new IllegalStateException("MemcacheClient must not be null.");
    }
    //TODO check memcache state

  }

  private void updateCaches() {
    if(caches != null){
      for(Cache cache : caches){
        if(cache instanceof MemcacheCache){
          MemcacheCache memcacheCache = (MemcacheCache)cache;
          memcacheCache.setClient(client);
        }
      }
    }

  }

}

配置bean：

<bean id="cacheManager" class="com.youboy.cshop.utils.memcache.MemcacheCacheManager">
    <property name="client" value="memcachedClient"/>
    <property name="caches">
        <set>
            <bean class="com.youboy.cshop.utils.memcache.MemcacheCache">
                <property name="name" value="testCache"/>
                <property name="client" ref="memcachedClient"/>
            </bean>
        </set>
    </property>
</bean>

其中memcachedClient爲你memcache的客戶端，你可以配置多個MemcacheCache，配置完這裏你就你就可以把@Cacheable(value="testCache")添加到方法那來緩存執行結果，這裏value="testCache"的值必須和上面bean文件配置的一致，否則無法緩存。這只是做了個簡單的集成，還有很多要完善的，比如連接時檢查memcache狀態。