Class CachingStorage

src/main/java/com/trsst/server/CachingStorage.java:31–229

A simple passthrough that caches read operations. @author mpowers

 * @author mpowers
 */
public class CachingStorage implements Storage {

    /**
     * Persistent storage delegate used to fetch items not in cache and to
     * passthrough write operations.
     */
    private Storage persistentStorage;

    /**
     * Persistent storage delegate used to fetch items not in cache and to
     * passthrough write operations.
     */
    private ConcurrentMap<String, Object> cache;

    /**
     * Manages index and calls to the specified storage delegate to handle
     * individual feed, entry, and resource persistence.
     * 
     * @param delegate
     * @throws IOException
     */
    public CachingStorage(Storage delegate) throws IOException {
        persistentStorage = delegate;
        cache = new ConcurrentLinkedHashMap.Builder<String, Object>()
                .maximumWeightedCapacity(256).build();

    }

    private static char DELIMITER = 0;

    private static final String tokenize(Object... args) {
        StringBuffer buf = new StringBuffer();
        for (Object arg : args) {
            buf.append(arg).append(DELIMITER);
        }
        return buf.toString();
    }

    private static Object NOT_FOUND = "NOT_FOUND";

    private Object get(String token) {
        if (cache.containsKey(token)) {
            return cache.get(token);
        }
        return NOT_FOUND;
    }

    private void put(String token, Object value) {
        cache.put(token, value);
    }

    private void purge(String prefix) {
        // purge all keys with prefix
        for (String key : cache.keySet()) {
            if (key.startsWith(prefix)) {
                cache.remove(key);
            }
        }