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second round of cache cleanups - got rid of that bogus pile of monkey spew

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that was ReferenceCache, replaced it with the much cleaner ObjectCache (it
uses SoftReferences so that the "sweep" operation is pretty much automatic)
This commit is contained in:
Eric J. Bowersox
2001-11-15 00:30:24 +00:00
parent e290ce2a8c
commit 0437cc7b92
21 changed files with 536 additions and 595 deletions
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195
src/com/silverwrist/util/cache/ObjectCache.java vendored Normal file
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@@ -0,0 +1,195 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.cache;
import java.lang.ref.*;
import java.util.*;
/**
* A chache which stores objects by key value, and is capable of creating them given an instance of
* <CODE>ObjectFactory</CODE> to do the creating. The cache uses <CODE>SoftReferences</CODE> which can
* automatically be removed by the garbage collector if necessary.
*
* @author Eric J. Bowersox &lt;erbo@silcom.com&gt;
* @version X
* @see ObjectFactory
* @see java.lang.ref.SoftReference
*/
public class ObjectCache
{
/*--------------------------------------------------------------------------------
* Attributes
*--------------------------------------------------------------------------------
*/
private HashMap the_data = new HashMap(); // the actual underlying map
private ObjectFactory factory; // used to create new objects
private ReferenceQueue rq = new ReferenceQueue(); // where our references go when they die
private ArrayList sweeper = new ArrayList(); // temporary used in doing sweeps
/*--------------------------------------------------------------------------------
* Constructor
*--------------------------------------------------------------------------------
*/
/**
* Creates a new <CODE>ObjectCache</CODE>.
*
* @param factory The factory object used to create new objects when <CODE>getOrCreate</CODE> is called.
* @exception java.lang.NullPointerException The object factory passed in is <CODE>null</CODE>.
*/
public ObjectCache(ObjectFactory factory)
{
if (factory==null)
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
* collector and removing them from the map. Should be called fairly often, to minimize wasted
* hashmap slots.
*/
private synchronized void doSweep()
{
Set entries = the_data.entrySet(); // used to find entries with the specified value
Reference r = rq.poll(); // reference that's been cleared
Iterator it;
while (r!=null)
{ // 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
*--------------------------------------------------------------------------------
*/
/**
* Retrieves an object from the cache.
*
* @param key The key value of the object to look up.
* @return The corresponding object value, or <CODE>null</CODE> if that object isn't in the cache.
*/
public synchronized Object get(Object key)
{
doSweep();
SoftReference r = (SoftReference)(the_data.get(key));
return ((r==null) ? null : r.get());
} // end get
/**
* Retrieves an object from the cache, creating it if it doesn't already exist.
*
* @param key The key value of the object to look up or create.
* @return The corresponding object value.
* @exception com.silverwrist.util.cache.ObjectFactoryException If an exception occurred while creating
* a new object.
* @see ObjectFactory#newObject(java.lang.Object)
*/
public synchronized Object getOrCreate(Object key) throws ObjectFactoryException
{
doSweep();
SoftReference r = (SoftReference)(the_data.get(key));
Object rc = ((r==null) ? null : r.get());
if (rc==null)
{ // attempt to create a new object
rc = factory.newObject(key);
if (rc!=null)
{ // clear the old reference, throw it away, and put in a new one
if (r!=null)
r.clear();
r = new SoftReference(rc,rq);
the_data.put(key,r);
} // end if
} // end if
return rc;
} // end getOrCreate
/**
* Registers a newly-created object with the cache.
*
* @param key The key value to register this object with.
* @param data The object to be registered.
* @exception com.silverwrist.util.cache.ObjectCacheException If an object with that key value already
* exists in the cache.
*/
public synchronized void register(Object key, Object data)
{
doSweep();
SoftReference old = (SoftReference)(the_data.get(key));
if ((old!=null) && (old.get()!=null))
throw new ObjectCacheException("object already in cache",key);
the_data.put(key,new SoftReference(data,rq));
if (old!=null)
old.clear();
} // end register
/**
* Detaches an object from the cache.
*
* @param key Key value of the object to be detached.
*/
public synchronized void detach(Object key)
{
doSweep();
SoftReference old = (SoftReference)(the_data.remove(key));
if (old!=null)
old.clear();
} // end detach
} // end class ObjectCache

29
src/com/silverwrist/util/rcache/ReferenceCacheException.java → src/com/silverwrist/util/cache/ObjectCacheException.java vendored
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@@ -15,23 +15,37 @@
*
* Contributor(s):
*/
package com.silverwrist.util.rcache;
package com.silverwrist.util.cache;
public class ReferenceCacheException extends RuntimeException
/**
* An exception thrown by the <CODE>ObjectCache</CODE> in unusual circumstances. The main reason why this
* exception would be thrown is if some code tried to register an object that was already in the cache.
*
* @author Eric J. Bowersox &lt;erbo@silcom.com&gt;
* @version X
* @see ObjectCache#register(java.lang.Object,java.lang.Object)
*/
public class ObjectCacheException extends RuntimeException
{
/*--------------------------------------------------------------------------------
* Attributes
*--------------------------------------------------------------------------------
*/
private Object keyval;
private Object keyval; // key value
/*--------------------------------------------------------------------------------
* Constructor
*--------------------------------------------------------------------------------
*/
public ReferenceCacheException(String msg, Object keyval)
/**
* Constructs a new <CODE>ObjectCacheException</CODE>.
*
* @param msg The message to include with this exception.
* @param keyval The key value of the object that caused this exception to be generated.
*/
public ObjectCacheException(String msg, Object keyval)
{
super("[keyval " + keyval.toString() + "]: " + msg);
this.keyval = keyval;
@@ -43,10 +57,15 @@ public class ReferenceCacheException extends RuntimeException
*--------------------------------------------------------------------------------
*/
/**
* Returns the key value of the object that caused this exception to be generated.
*
* @return The key value of the object that caused this exception to be generated.
*/
public Object getKeyVal()
{
return keyval;
} // end getKeyVal
} // end class ReferenceCacheException
} // end class ObjectClassException

41
src/com/silverwrist/util/cache/ObjectFactory.java vendored Normal file
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@@ -0,0 +1,41 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.cache;
/**
* An interface which is used by <CODE>ObjectCache</CODE> to create new objects which match a specified
* key. An instance of an object implementing this interface must be specified to the constructor
* of <CODE>ObjectFactory</CODE>.
*
* @see ObjectCache#Constructor(com.silverwrist.util.cache.ObjectFactory)
* @see ObjectCache#getOrCreate(java.lang.Object)
*/
public interface ObjectFactory
{
/**
* Creates a new instance of an object for the object cache.
*
* @param key The key value of the new object to be created.
* @return The new object instance.
* @exception com.silverwrist.util.cache.ObjectFactoryException An exception was thrown by the
* constructors and/or methods called by <CODE>newObject</CODE>; it is wrapped in this exception.
* @see ObjectCache#getOrCreate(java.lang.Object)
*/
public abstract Object newObject(Object key) throws ObjectFactoryException;
} // end interface ObjectFactory

126
src/com/silverwrist/util/cache/ObjectFactoryException.java vendored Normal file
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@@ -0,0 +1,126 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.cache;
import java.io.PrintStream;
import java.io.PrintWriter;
/**
* The exception which may be thrown by <CODE>ObjectFactory.newObject</CODE>, which wraps any exception
* that might be thrown by constructors or other method calls within the method.
*
* @author Eric J. Bowersox &lt;erbo@silcom.com&gt;
* @version X
* @see ObjectFactory#newObject(java.lang.Object)
*/
public class ObjectFactoryException extends Exception
{
/*--------------------------------------------------------------------------------
* Attributes
*--------------------------------------------------------------------------------
*/
private Throwable inner = null; // internal "root cause" exception
/*--------------------------------------------------------------------------------
* Constructor
*--------------------------------------------------------------------------------
*/
/**
* Creates a new <CODE>ObjectFactoryException</CODE>.
*
* @param t Exception being wrapped by this one.
*/
public ObjectFactoryException(Throwable t)
{
super("Error creating new object: " + t.getMessage());
inner = t;
} // end constructor
/*--------------------------------------------------------------------------------
* Overrides from class Throwable
*--------------------------------------------------------------------------------
*/
/**
* Prints this exception and its backtrace to the standard error stream. Also prints the backtrace
* of any "wrapped" exception.
*
* @see java.lang.System#err
*/
public void printStackTrace()
{
this.printStackTrace(System.err);
} // end printStackTrace
/**
* Prints this exception and its backtrace to the specified <CODE>PrintStream</CODE>. Also prints the
* backtrace of any "wrapped" exception.
*
* @param s <CODE>PrintStream</CODE> to use for output.
*/
public void printStackTrace(PrintStream s)
{
super.printStackTrace(s);
if (inner!=null)
{ // print the inner stack trace
s.print("Root cause: ");
inner.printStackTrace(s);
} // end if
} // end printStackTrace
/**
* Prints this exception and its backtrace to the specified <CODE>PrintWriter</CODE>. Also prints the
* backtrace of any "wrapped" exception.
*
* @param s <CODE>PrintWriter</CODE> to use for output.
*/
public void printStackTrace(PrintWriter s)
{
super.printStackTrace(s);
if (inner!=null)
{ // print the inner stack trace
s.print("Root cause: ");
inner.printStackTrace(s);
} // end if
} // end printStackTrace
/*--------------------------------------------------------------------------------
* External operations
*--------------------------------------------------------------------------------
*/
/**
* Returns the exception wrapped by this exception, or <CODE>null</CODE> if there is none.
*
* @return See above.
*/
public Throwable getException()
{
return inner;
} // end getException
} // end class ObjectFactoryException

161
src/com/silverwrist/util/rcache/ReferenceCache.java
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@@ -1,161 +0,0 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.rcache;
import java.util.*;
public class ReferenceCache
{
/*--------------------------------------------------------------------------------
* Attributes
*--------------------------------------------------------------------------------
*/
private HashMap the_data;
/*--------------------------------------------------------------------------------
* Constructor
*--------------------------------------------------------------------------------
*/
public ReferenceCache()
{
the_data = new HashMap();
} // end constructor
/*--------------------------------------------------------------------------------
* External operations
*--------------------------------------------------------------------------------
*/
public synchronized ReferencedData get(Object key)
{
ReferencedData rc = (ReferencedData)(the_data.get(key));
if (rc!=null)
rc.rd_addRef();
return rc;
} // end get
public synchronized ReferencedData getOrCreate(Object key, ReferencedDataBuilder builder)
throws ReferencedDataBuilderException
{
ReferencedData rc = (ReferencedData)(the_data.get(key));
if (rc==null)
{ // use the builder to build one
rc = builder.build(key);
if (rc!=null)
the_data.put(key,rc);
} // end if
else // just add a reference
rc.rd_addRef();
return rc;
} // end getOrCreate
public void register(ReferencedData data)
{
Object key = data.rd_getKey();
synchronized (this)
{ // see if it's in the cache, if not, add it
if (the_data.get(key)!=null)
throw new ReferenceCacheException("object already in cache",key);
// dump it in the object cache
the_data.put(key,data);
} // end synchronized block
} // end register
public synchronized void detach(Object key)
{
the_data.remove(key);
} // end detach
public void sweep()
{
int count = 0;
synchronized (this)
{ // bail out early if possible
if (the_data.size()==0)
return;
// provide a storage bin for all keys we decide to 86
Object keyzap[] = new Object[the_data.size()];
Iterator it = the_data.values().iterator();
while (it.hasNext())
{ // check each value we contain in turn
ReferencedData rd = (ReferencedData)(it.next());
if (rd.rd_unreferenced())
keyzap[count++] = rd.rd_getKey();
} // end while
for (int i=0; i<count; i++)
the_data.remove(keyzap[i]);
} // end synchronized block
} // end sweep
public List sweepReturn()
{
ArrayList rc = new ArrayList();
int count = 0;
synchronized (this)
{ // bail out early if possible
if (the_data.size()>0)
{ // provide a storage bin for all keys we decide to 86
Object keyzap[] = new Object[the_data.size()];
Iterator it = the_data.values().iterator();
while (it.hasNext())
{ // check each value we contain in turn
ReferencedData rd = (ReferencedData)(it.next());
if (rd.rd_unreferenced())
keyzap[count++] = rd.rd_getKey();
else
{ // add another reference and tack it onto the list
rd.rd_addRef();
rc.add(rd);
} // end else
} // end while
for (int i=0; i<count; i++)
the_data.remove(keyzap[i]);
} // end if
} // end synchronized block
return Collections.unmodifiableList(rc);
} // end sweepReturn
} // end ReferenceCache

30
src/com/silverwrist/util/rcache/ReferencedData.java
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@@ -1,30 +0,0 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.rcache;
public interface ReferencedData
{
public abstract int rd_addRef();
public abstract int rd_release();
public abstract boolean rd_unreferenced();
public abstract Object rd_getKey();
} // end interface ReferencedData

24
src/com/silverwrist/util/rcache/ReferencedDataBuilder.java
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@@ -1,24 +0,0 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.rcache;
public interface ReferencedDataBuilder
{
public abstract ReferencedData build(Object key) throws ReferencedDataBuilderException;
} // end interface ReferencedDataBuilder

52
src/com/silverwrist/util/rcache/ReferencedDataBuilderException.java
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@@ -1,52 +0,0 @@
/*
* The contents of this file are subject to the Mozilla Public License Version 1.1
* (the "License"); you may not use this file except in compliance with the License.
* You may obtain a copy of the License at <http://www.mozilla.org/MPL/>.
*
* Software distributed under the License is distributed on an "AS IS" basis, WITHOUT
* WARRANTY OF ANY KIND, either express or implied. See the License for the specific
* language governing rights and limitations under the License.
*
* The Original Code is the Venice Web Communities System.
*
* 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.
*
* Contributor(s):
*/
package com.silverwrist.util.rcache;
public class ReferencedDataBuilderException extends Exception
{
/*--------------------------------------------------------------------------------
* Attributes
*--------------------------------------------------------------------------------
*/
private Exception target;
/*--------------------------------------------------------------------------------
* Constructors
*--------------------------------------------------------------------------------
*/
public ReferencedDataBuilderException(Exception target)
{
super("Error building new object: " + target.getMessage());
this.target = target;
} // end constructor
/*--------------------------------------------------------------------------------
* External operations
*--------------------------------------------------------------------------------
*/
public Exception getTarget()
{
return target;
} // end getTarget
} // end class ReferencedDataBuilderException