GaeMemcache.java

package com.google.sitebricks.binding;

import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.servlet.SessionScoped;
import net.jcip.annotations.ThreadSafe;

import javax.servlet.http.HttpSession;
import java.io.Serializable;

import com.google.appengine.api.memcache.MemcacheService;
import com.google.appengine.api.memcache.MemcacheServiceFactory;
import com.google.appengine.api.memcache.Expiration;

/**
 * Used to store binding (or forwarding) information between successive requests. This
 * cache is an alternative to the default {@linkplain com.google.sitebricks.binding.HttpSessionFlashCache} in that it
 * explicitly uses the appengine Memcache API.
 *
 * @author Dhanji R. Prasanna (dhanji@gmail.com)
 *                             (modified by so)
 */
@ThreadSafe @SessionScoped
public class GaeMemcache implements FlashCache {
//public final class GaeFlashCache implements FlashCache {
  private final Provider<HttpSession> session;

  private final MemcacheService memcache = MemcacheServiceFactory.getMemcacheService();

  @Inject
  GaeMemcache(Provider<HttpSession> session) {
    this.session = session;
    memcache.setNamespace(session.get().getId());
  }

  @SuppressWarnings("unchecked")
  public <T> T get(String key) {    
    return (T) memcache.get(key);
  }

  public <T> T remove(String key) {
    @SuppressWarnings("unchecked")
    T previous = (T) get(key);
    memcache.delete(key);
    return previous;
  }

  public <T> void put(String key, T t) {
    Expiration x = Expiration.byDeltaSeconds(session.get().getMaxInactiveInterval());
    memcache.put(key, t, x);
  }
}