introduced the use of the Jakarta Commons Collections - revamped ObjectCache

to include an LRU hard reference map and simplified it greatly in the process

lib/.gitignore

@@ -1,4 +1,5 @@
 bsf.jar
+commons-collections.jar
 jacl.jar
 jakarta-regexp*.jar
 js.jar

lib/README.lib

@@ -6,6 +6,8 @@ compatible with the versions specified here.
 
 Library                         Version  File Name(s)                      Install To
 -------------------------------------------------------------------------------------------------
+Apache Jakarta Commons          2.0      commons-collections.jar           Venice "lib" subdirectory
+    Collections
 Apache Jakarta Regexp           1.2      jakarta-regexp-1.2.jar            Venice "lib" subdirectory
 Apache LOG4J                    1.1.3    log4j.jar                         Venice "lib" subdirectory
 Bean Scripting Framework        2.2      bsf.jar                           Venice "lib" subdirectory

src/com/silverwrist/util/cache/ObjectCache.java

@@ -11,14 +11,13 @@
  * 
  * The Initial Developer of the Original Code is Eric J. Bowersox <erbo@silcom.com>,
  * for Silverwrist Design Studios.  Portions created by Eric J. Bowersox are
- * Copyright (C) 2001 Eric J. Bowersox/Silverwrist Design Studios.  All Rights Reserved.
+ * Copyright (C) 2001-02 Eric J. Bowersox/Silverwrist Design Studios.  All Rights Reserved.
  * 
  * Contributor(s): 
  */
 package com.silverwrist.util.cache;
 
-import java.lang.ref.*;
+import org.apache.commons.collections.*;
-import java.util.*;
 
 /**
  * A chache which stores objects by key value, and is capable of creating them given an instance of
@@ -28,7 +27,6 @@ import java.util.*;
  * @author Eric J. Bowersox &lt;erbo@silcom.com&gt;
  * @version X
  * @see ObjectFactory
- * @see java.lang.ref.SoftReference
  */
 public class ObjectCache
 {
@@ -37,10 +35,9 @@ public class ObjectCache
    *--------------------------------------------------------------------------------
    */
 
-  private HashMap the_data = new HashMap();           // the actual underlying map
+  private SoftRefHashMap the_data = new SoftRefHashMap();  // actual main data store
-  private ObjectFactory factory;                      // used to create new objects
+  private LRUMap mru_cache;                                // most-recently-used map
-  private ReferenceQueue rq = new ReferenceQueue();   // where our references go when they die
+  private ObjectFactory factory;                           // used to create new objects
-  private ArrayList sweeper = new ArrayList();        // temporary used in doing sweeps
 
   /*--------------------------------------------------------------------------------
    * Constructor
@@ -55,57 +52,25 @@ public class ObjectCache
    */
   public ObjectCache(ObjectFactory factory)
   {
-    if (factory==null)
+    this(factory,5);
-      throw new NullPointerException("object factory cannot be null!");
-    this.factory = factory;
 
   } // end constructor
 
-  /*--------------------------------------------------------------------------------
-   * Internal operations
-   *--------------------------------------------------------------------------------
-   */
-
   /**
-   * "Sweeps" the cache by taking all references that have been cleared and queued by the garbage
+   * Creates a new <CODE>ObjectCache</CODE>.
-   * collector and removing them from the map.  Should be called fairly often, to minimize wasted
+   *
-   * hashmap slots.
+   * @param factory The factory object used to create new objects when <CODE>getOrCreate</CODE> is called.
+   * @param lru_size How many objects to maintain hard references to.
+   * @exception java.lang.NullPointerException The object factory passed in is <CODE>null</CODE>.
    */
-  private synchronized void doSweep()
+  public ObjectCache(ObjectFactory factory, int lru_size)
   {
-    Set entries = the_data.entrySet();  // used to find entries with the specified value
+    if (factory==null)
-    Reference r = rq.poll();            // reference that's been cleared
+      throw new NullPointerException("object factory cannot be null!");
-    Iterator it;
+    this.factory = factory;
+    this.mru_cache = new LRUMap(lru_size);
 
-    while (r!=null)
+  } // end constructor
-    { // look for this reference in our hash map
-      it = entries.iterator();
-      while (it.hasNext())
-      { // look for the map entry containing the reference
-	Map.Entry ntry = (Map.Entry)(it.next());
-	if (r==(Reference)(ntry.getValue()))
-	{ // found the entry with this reference - nuke it
-	  sweeper.add(ntry.getKey());
-	  break;  // don't need to take this loop any farther
-
-	} // end if
-
-      } // end while
-
-      r = rq.poll();  // get the next cleared reference
-
-    } // end while
-
-    if (sweeper.isEmpty())
-      return;  // no entries to remove
-
-    // Remove all the corresponding keys from the hashmap.
-    it = sweeper.iterator();
-    while (it.hasNext())
-      the_data.remove(it.next());
-    sweeper.clear();  // reset for next time
-
-  } // end doSweep
 
   /*--------------------------------------------------------------------------------
    * External operations
@@ -120,9 +85,17 @@ public class ObjectCache
    */
   public synchronized Object get(Object key)
   {
-    doSweep();
+    the_data.purge();
-    SoftReference r = (SoftReference)(the_data.get(key));
+    Object rc = mru_cache.get(key);
-    return ((r==null) ? null : r.get());
+    if (rc==null)
+    { // retrieve from main map, poke back into cache
+      rc = the_data.get(key);
+      if (rc!=null)
+	mru_cache.put(key,rc);
+
+    } // end if
+
+    return rc;
 
   } // end get
 
@@ -137,18 +110,14 @@ public class ObjectCache
    */
   public synchronized Object getOrCreate(Object key) throws ObjectFactoryException
   {
-    doSweep();
+    Object rc = this.get(key);
-    SoftReference r = (SoftReference)(the_data.get(key));
-    Object rc = ((r==null) ? null : r.get());
     if (rc==null)
-    { // attempt to create a new object
+    { // create a new object
       rc = factory.newObject(key);
       if (rc!=null)
-      { // clear the old reference, throw it away, and put in a new one
+      { // stash in both main map and cache
-	if (r!=null)
+	the_data.put(key,rc);
-	  r.clear();
+	mru_cache.put(key,rc);
-	r = new SoftReference(rc,rq);
-	the_data.put(key,r);
 
       } // end if
 
@@ -168,13 +137,11 @@ public class ObjectCache
    */
   public synchronized void register(Object key, Object data)
   {
-    doSweep();
+    the_data.purge();
-    SoftReference old = (SoftReference)(the_data.get(key));
+    if (the_data.get(key)!=null)
-    if ((old!=null) && (old.get()!=null))
       throw new ObjectCacheException("object already in cache",key);
-    the_data.put(key,new SoftReference(data,rq));
+    the_data.put(key,data);
-    if (old!=null)
+    mru_cache.put(key,data);
-      old.clear();
 
   } // end register
 
@@ -185,11 +152,18 @@ public class ObjectCache
    */
   public synchronized void detach(Object key)
   {
-    doSweep();
+    mru_cache.remove(key);
-    SoftReference old = (SoftReference)(the_data.remove(key));
+    the_data.remove(key);
-    if (old!=null)
+    the_data.purge();
-      old.clear();
 
   } // end detach
 
+  public synchronized void shutdown()
+  {
+    mru_cache.clear();
+    the_data.clear();
+    the_data.purge();
+
+  } // end shutdown
+
 } // end class ObjectCache

src/com/silverwrist/venice/core/impl/CommunityUserContextImpl.java

@@ -158,8 +158,6 @@ class CommunityUserContextImpl implements CommunityContext, CommunityBackend
       if (deleted)
 	throw new DataException("This community has been deleted.");
       data = env.getEngine().getCommunityDataObject(cid);
-      if (data!=null)
-	env.getUser().saveMRU("community",data);
 
       // clear cache when we get the real data
       cache = null;
@@ -179,8 +177,6 @@ class CommunityUserContextImpl implements CommunityContext, CommunityBackend
       try
       { // attempt to load the CommunityDataObject
 	data = env.getEngine().getCommunityDataObject(cid);
-	if (data!=null)
-	  env.getUser().saveMRU("community",data);
 
       } // end try
       catch (DataException e)

src/com/silverwrist/venice/core/impl/ConferenceUserContextImpl.java

@@ -219,8 +219,6 @@ class ConferenceUserContextImpl implements ConferenceContext, ConferenceBackend
       if (deleted)
 	throw new DataException("This conference has been deleted.");
       confdata = env.getCommunity().getConferenceDataObject(confid);
-      if (confdata!=null)
-	env.getUser().saveMRU("conf",confdata);
 
       // clear cache when we get the real confdata
       cache = null;
@@ -241,8 +239,6 @@ class ConferenceUserContextImpl implements ConferenceContext, ConferenceBackend
       try
       { // attempt to load the ConferenceCommunityContext
 	confdata = env.getCommunity().getConferenceDataObject(confid);
-	if (confdata!=null)
-	  env.getUser().saveMRU("conf",confdata);
 
       } // end try
       catch (DataException e)