How can I disable serialization in Wicket 1.5?

Question

I want to turn off serialization in my Wicket app and store all page/session information in RAM. My application has a very small number of users (generally 1); I do not need

Answer 1

I want to improve Jesse's answer. Below is a thread-safe implementation of IPageStore with internal "Least Recently Inserted" cache (keeps at most 5 recently accessed stateful pages per session):

public class CustomPageStore implements IPageStore {

private static final Logger logger = LoggerFactory.getLogger(CustomPageStore.class);

private static final int MEDIAN_OF_NUMBER_OF_SESSIONS = 6000;

private ConcurrentMap> cache = new ConcurrentHashMap<>(MEDIAN_OF_NUMBER_OF_SESSIONS);

@Override
public void destroy() {
    cache.clear();
}

@Override
public IManageablePage getPage(final String sessionId, int pageId) {
    final Map sessionCache = getSessionCache(sessionId);
    final RequestCycle requestCycle = RequestCycle.get();
    if (sessionCache == null) {
        logger.warn("Missing cache. SessionId: {}, pageId: {}, URL: {}", sessionId, pageId, requestCycle == null ? StringUtils.EMPTY : requestCycle.getRequest().getUrl());
        return null;
    }

    final IManageablePage page;
    //noinspection SynchronizationOnLocalVariableOrMethodParameter
    synchronized (sessionCache) {
        page = sessionCache.get(pageId);
    }

    if (page == null && logger.isDebugEnabled()) {
        logger.debug("Missed page. SessionId: {}, pageId: {}, URL: {}", sessionId, pageId, requestCycle == null ? StringUtils.EMPTY : requestCycle.getRequest().getUrl());
    }

    return page;
}

@Override
public void removePage(final String sessionId, int pageId) {
    final Map sessionCache = getSessionCache(sessionId);
    if (sessionCache != null) {
        //noinspection SynchronizationOnLocalVariableOrMethodParameter
        synchronized (sessionCache) {
            sessionCache.remove(pageId);
        }
    }
}

@Override
public void storePage(final String sessionId, IManageablePage page) {
    final LinkedHashMap sessionCache = getOrCreateSessionCache(sessionId);
    final int pageId = page.getPageId();
    //noinspection SynchronizationOnLocalVariableOrMethodParameter
    synchronized (sessionCache) {
        if (sessionCache.containsKey(pageId)) {
            // do this to change insertion order and update least inserted entry
            sessionCache.remove(pageId);
            sessionCache.put(pageId, page);
        } else {
            sessionCache.put(pageId, page);
        }
    }
}

@Override
public void unbind(final String sessionId) {
    cache.remove(sessionId);
}

@Override
public Serializable prepareForSerialization(String sessionId, Object page) {
    return null;
}

@Override
public Object restoreAfterSerialization(Serializable serializable) {
    return null;
}

@Override
public IManageablePage convertToPage(final Object page) {
    return (IManageablePage) page;
}

@Nullable
private Map getSessionCache(final String sessionId) {
    return cache.get(sessionId);
}

@Nonnull
private CustomLinkedHashMap getOrCreateSessionCache(final String sessionId) {
    return cache.computeIfAbsent(sessionId, s -> new CustomLinkedHashMap<>());
}

/** Mimics "least recently inserted" cache */
private static class CustomLinkedHashMap extends LinkedHashMap {

    /** use this parameter to control memory consumption and frequency of appearance of PageExpiredException */
    private static final int MAX_PAGES_PER_SESSION = 5;

    @Override
    protected boolean removeEldestEntry(final Map.Entry eldest) {
        return size() > MAX_PAGES_PER_SESSION;
    }
}
}