spring集成memcache 示例一

spring3.1.0开始支持注解方式的缓存实现，非常方便，不过它目前只支持java内置的ConcurrentMap和ehcache这两种缓存方式，因为项目用到memcache，就想把memcache集成到spring内置的缓存中，使memcache也能用注解方式来调用。于是参考ehcache的集成方式，把memcache集成到项目中。spring把所有缓存都抽象为一个cache，相当于一个缓存集合，即spring缓存注解@Cacheable(value="xxx")中xxx对应的结果集合。首先我们要实现Cache这个接口，memcache的java客户端我们用的是com.danga.MemCached.MemCachedClient这个，代码如下：

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;
  }

}

然后是要扩展AbstractCacheManager这个缓存管理抽象类，它主要负责生成和读取Cache，代码如下：

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为你memcache的客户端，你可以配置多个MemcacheCache，配置完这里你就你就可以把@Cacheable(value="testCache")添加到方法那来缓存执行结果，这里value="testCache"的值必须和上面bean文件配置的一致，否则无法缓存。这只是做了个简单的集成，还有很多要完善的，比如连接时检查memcache状态。