CachingPage.java

// Copyright (C) 2003-2009 by Object Mentor, Inc. All rights reserved.
// Released under the terms of the CPL Common Public License version 1.0.

package fitnesse.wiki;

import java.lang.ref.SoftReference;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import util.TimeMeasurement;

public abstract class CachingPage extends CommitingPage {
  private static final long serialVersionUID = 1L;

  public static int cacheTime = 3000;

  protected Map<String, WikiPage> children = new HashMap<String, WikiPage>();
  private transient SoftReference<PageData> cachedData;
  private transient TimeMeasurement cachedTime;

  public CachingPage(String name, WikiPage parent) {
    super(name, parent);
    addExtention(new VirtualCouplingExtension(this));
  }

  public abstract boolean hasChildPage(String pageName);

  protected abstract WikiPage createChildPage(String name);

  protected abstract void loadChildren();

  protected abstract PageData makePageData();

  public WikiPage addChildPage(String name) {
    WikiPage page = createChildPage(name);
    children.put(name, page);
    return page;
  }

  @Override
  public List<WikiPage> getNormalChildren() {
    loadChildren();
    return getCachedChildren();
  }

  public List<WikiPage> getCachedChildren() {
    return new ArrayList<WikiPage>(children.values());
  }

  public void removeChildPage(String name) {
    if (hasCachedSubpage(name))
      children.remove(name);
  }

  @Override
  public WikiPage getNormalChildPage(String name) {
    if (hasCachedSubpage(name) || hasChildPage(name))
      return children.get(name);
    else
      return null;
  }

  protected boolean hasCachedSubpage(String name) {
    return children.containsKey(name);
  }

  public PageData getData() {
    if (cachedDataExpired()) {
      ReloadCache();
    }
    return new PageData(getCachedData());
  }

  private void ReloadCache() {
    //if (getCachedData() == null) System.out.println("cache null " + (getName() != null ? getName() : "?"));
    //else if (cachedTime.elapsed() >= cacheTime) System.out.println("cache expired " + (getName() != null ? getName() : "?"));
    PageData data = makePageData();
    //System.out.println("reload " + getName() + " " + data.getContent().length());
    setCachedData(data);
  }

  public ReadOnlyPageData readOnlyData() {
    if (getCachedData() == null) {
      ReloadCache();
    }
    return getCachedData();
  }

  private boolean cachedDataExpired() {
    return getCachedData() == null || cachedTime.elapsed() >= cacheTime;
  }

  public void dumpExpiredCachedData() {
    if (cachedDataExpired())
      clearCache();
  }

  @Override
  public VersionInfo commit(PageData data) {
    VersionInfo versionInfo = super.commit(data);
    setCachedData(makePageData());
    return versionInfo;
  }

  private void setCachedData(PageData data) {
    if (cachedData != null)
      cachedData.clear();
    cachedData = new SoftReference<PageData>(data);
    cachedTime = new TimeMeasurement().start();
  }

  public PageData getCachedData() {
    if (cachedData != null)
      return cachedData.get();
    else
      return null;
  }

  public void clearCache() {
    cachedData.clear();
    cachedData = null;
  }
}