[gnizr commit] r936 - trunk/gnizr-core/src/main/java/com/gnizr/core/bookmark

[codesite...@google.com]

Author: harry...@gmail.com
Date: Wed Jun 18 12:22:34 2008
New Revision: 936

Modified:
trunk/gnizr-core/src/main/java/com/gnizr/core/bookmark/PopularBookmarks.java

Log:
added locking of cache generation. impl not complete.

Modified: trunk/gnizr-core/src/main/java/com/gnizr/core/bookmark/PopularBookmarks.java
==============================================================================
---
trunk/gnizr-core/src/main/java/com/gnizr/core/bookmark/PopularBookmarks.java (original)
+++
trunk/gnizr-core/src/main/java/com/gnizr/core/bookmark/PopularBookmarks.java
Wed Jun 18 12:22:34 2008
@@ -1,21 +1,31 @@
package com.gnizr.core.bookmark;

import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.apache.log4j.Logger;

+import com.gnizr.core.util.GnizrDaoUtil;
import com.gnizr.db.dao.Bookmark;
import com.gnizr.db.dao.GnizrDao;
import com.gnizr.db.dao.bookmark.BookmarkDao;

/**
- * Class for finding popular bookmarks saved by users in a gnizr community.
+ * Class for finding popular bookmarks saved by users in a gnizr
community. This class
+ * implements a data caching mechanism that can reduce database
accesses. When the caching
+ * is turned on, data of popular bookmarks are fetched and then stored
in the memory
+ * for a pre-defined period of time. When the cache data is expired, a
fresh copy of
+ * the data is fetched from the database.
*
* @author Harry Chen
- *
+ * @since 2.5.0
*/
public class PopularBookmarks implements Serializable{

@@ -26,21 +36,104 @@

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

+ private static final int ALL_TIME = 1;
+ private ReentrantReadWriteLock lockOfAllTime = new ReentrantReadWriteLock();
+
+ //private static final int PAST_24_H = 2;
+
+ //private static final int PAST_WEEK = 3;
+
+
private BookmarkDao bookmarkDao;

+ private ConcurrentMap<Integer, Cache> cacheMap;
+
+ private int cacheExpireInMinutes;
+
/**
* Creates an instance of this class with a defined
<code>GnizrDao</code> object.
* @param gnizrDao an instantiated <code>GnizrDao</code> object.
*/
public PopularBookmarks(GnizrDao gnizrDao){
this.bookmarkDao = gnizrDao.getBookmarkDao();
+ cacheMap = new ConcurrentHashMap<Integer, Cache>();
}

public List<Bookmark> getTop10AllTime(){
- logger.debug("getTop10AllTime popular bookmarks.");
- Date start = new GregorianCalendar(1900,1,1).getTime();
- Date end = GregorianCalendar.getInstance().getTime();
- return this.bookmarkDao.getPopularCommunityBookmarks(start,end,10);
+ logger.debug("getTop10AllTime popular bookmarks.");
+ List<Bookmark> bmarks = null;
+ lockOfAllTime.readLock().lock();
+ if(isCacheValid(ALL_TIME) == false){
+ lockOfAllTime.readLock().unlock();
+ lockOfAllTime.writeLock().lock();
+ if(isCacheValid(ALL_TIME) == false){
+ Date start = new GregorianCalendar(1900,1,1).getTime();
+ Date end = GnizrDaoUtil.getNow();
+ bmarks = this.bookmarkDao.getPopularCommunityBookmarks(start,end,10);
+ Cache cache = new Cache(bmarks,end);
+ cacheMap.put(ALL_TIME,cache);
+ }
+ lockOfAllTime.readLock().lock();
+ lockOfAllTime.writeLock().unlock();
+ }
+ bmarks = cacheMap.get(ALL_TIME).getBookmarks();
+ lockOfAllTime.readLock().unlock();
+ return bmarks;
}

+ private boolean isCacheValid(int cacheCode){
+ Cache cache = cacheMap.get(cacheCode);
+ if(cache == null){
+ return false;
+ }else{
+ Date lastUpdated = cache.getLastUpdated();
+ Calendar now = GregorianCalendar.getInstance();
+ now.add(Calendar.MINUTE, (-1*cacheExpireInMinutes));
+ if(now.before(lastUpdated) == true){
+ return true;
+ }
+ }
+ return false;
+ }
+
+
+ public int getCacheExpireInMinutes() {
+ return cacheExpireInMinutes;
+ }
+
+ public void setCacheExpireInMinutes(int cacheExpireInMinutes) {
+ this.cacheExpireInMinutes = cacheExpireInMinutes;
+ }
+
+ private class Cache {
+ private List<Bookmark> bookmarks;
+ private Date lastUpdated;
+
+ public Cache(){
+ this.bookmarks = new ArrayList<Bookmark>();
+ this.lastUpdated = null;
+ }
+
+ public Cache(List<Bookmark> bookmarks, Date lastUpdate){
+ this.bookmarks = bookmarks;
+ this.lastUpdated = lastUpdate;
+ }
+
+ public List<Bookmark> getBookmarks() {
+ return bookmarks;
+ }
+
+ public void setBookmarks(List<Bookmark> bookmarks) {
+ this.bookmarks = bookmarks;
+ }
+
+ public Date getLastUpdated() {
+ return lastUpdated;
+ }
+
+ public void setLastUpdated(Date lastUpdated) {
+ this.lastUpdated = lastUpdated;
+ }
+ }
+
}