Re: Object retention when using removeChild

[Thomas DeWeese]

Hi Daniel.

Spasojevic, Daniel wrote:

Firstly, I think that the Batik SVG toolkit is very good, and I have been very impressed with the overall quality and number of features implemented.

   Thanks.

I am having trouble removing nodes from a SVG document that has been
associated with a JSVGCanvas object. The problem is that although calling 
removeChild() stops the nodes from being displayed, it seems that the objects 
associated with that node are retained - preventing the removed nodes from being 
garbage collected. I am using Batik 1.5, the problem appears when using 1.4.1_02 and 
1.4.1_03 of Java, and under Windows 2000 and KDE on linux.
   Which Batik 1.5? Beta 5?

Hopefully this is due to a coding error on my part.
 

   One can always hope :)  However I think/know there is a memory leak 
here, I have found
and fixed at least one based on your information already.

I wrote a simple test program that built a SVG document that included a text element, associated it with a JSVGCanvas, then removed all child nodes of the document root. Using JProfiler, I found the following references to associated SVGOMTextElement (the format of this output is: name of the referant, number of references, total size of references):
 

   Thanks for taking the time to do this.  Good tests help a _lot_ I 
unfortuantely do not
have access to JProfiler.  Are you up for working through this with 
diffs etc?

--- Incoming references after removeChild()
 

I have categorized these:

Known (or strongly suspected) safe:

field e of org.apache.batik.bridge.SVGTextElementBridge	1	40 
field ownerElement of org.apache.batik.dom.GenericAttr	2	80
field parentNode of org.apache.batik.dom.GenericText	1	40
field target of field this$0 of org.apache.batik.dom.AbstractParentNode$ChildNodes
1	24
field this$0 of
org.apache.batik.dom.AbstractParentNode$ExtendedNamedNodeHashMap	1 24
field this$0 of
org.apache.batik.dom.AbstractParentNode$ExtendedNamedNodeHashMap	1 24
 

Now a known problem:

org.apache.batik.bridge.BridgeContext$EventListenerMememto
2	48
 

   This class is now using SoftReferences in my local copy so it will 
not keep the
object in memory.  This change did not effect proper function, I still 
need to add a
ReferenceQueue so we don't accumulate Mememto's.  This will probably be
committed to CVS tonight.

Unknown source:

class array content	6	784
field value of java.util.HashTable$Entry
1	24
 

   I am especially baffled by the array references.  The HashTable may 
(or may
or may not be) harmless.

These references are preventing the object from being garbage collected.
After many additions and removals during the execution of my application,
this causes a significant increase in the memory used.
 





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