added in memory cache and redis cache and marked them as application scoped

src/main/java/com/commafeed/backend/cache/RedisCacheService.java

@@ -0,0 +1,62 @@
+package com.commafeed.backend.cache;
+
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.TimeUnit;
+
+import javax.enterprise.context.ApplicationScoped;
+import javax.enterprise.inject.Alternative;
+
+import redis.clients.jedis.Jedis;
+import redis.clients.jedis.JedisPool;
+import redis.clients.jedis.JedisPoolConfig;
+import redis.clients.jedis.Pipeline;
+
+import com.commafeed.backend.model.Feed;
+import com.google.api.client.util.Lists;
+
+@Alternative
+@ApplicationScoped
+public class RedisCacheService extends CacheService {
+
+	private JedisPool pool = new JedisPool(new JedisPoolConfig(), "localhost");
+
+	@Override
+	public List<String> getLastEntries(Feed feed) {
+		List<String> list = Lists.newArrayList();
+		Jedis jedis = pool.getResource();
+		try {
+			String key = buildKey(feed);
+			Set<String> members = jedis.smembers(key);
+			for (String member : members) {
+				list.add(member);
+			}
+		} finally {
+			pool.returnResource(jedis);
+		}
+		return list;
+	}
+
+	@Override
+	public void setLastEntries(Feed feed, List<String> entries) {
+		Jedis jedis = pool.getResource();
+		try {
+			String key = buildKey(feed);
+
+			Pipeline pipe = jedis.pipelined();
+			pipe.del(key);
+			for (String entry : entries) {
+				pipe.sadd(key, entry);
+			}
+			pipe.expire(key, (int) TimeUnit.HOURS.toSeconds(24));
+			pipe.sync();
+		} finally {
+			pool.returnResource(jedis);
+		}
+	}
+
+	private String buildKey(Feed feed) {
+		return "feed:" + feed.getId();
+	}
+
+}