I took a look at this today.
My initial results were less than 200ms for the problem xml with the
default settings, but over 30 seconds if I set the "cdata-sections"
parameter to true before parsing.
I first tried replacing the String concatenation in the
CharacterDataImpl.appendData() method with a StringBuffer. This
reduced the parse time to around 10 seconds but that still seemed
unacceptably slow.
After profiling, I noticed that the problem appears to be that
appendData() is just being called far too many times due to the number
of line breaks in the xerces_performance_problem.xml file.
The scanData() method in org.apache.xerces.impl.XMLEntityScanner
divides up character data into each line rather than filling up the
whole buffer. This results in very small chunks of character data and
means that appendData() gets called too often.
I tried instructing the scanData() method to ignore line breaks in
character data, by commenting out these four lines:
else if (c == '\n' || (external && c == '\r')) {
fCurrentEntity.position--;
break;
}
This results in the full buffer being used and fixed the performance
problem (the problem xml file parsed in well under 1 second).
Unfortunately removing this code has the side effect of breaking some
other things (e.g. the Locator), but perhaps someone more familiar
with the XMLEntityScanner can suggest a way to fix this.
In the meantime, a temporary workaround would be to remove line breaks
from your CDATA in your problematic xml files before parsing.
2009/7/6 Bene (JIRA) <[email protected]>:
>
> [
> https://issues.apache.org/jira/browse/XERCESJ-1382?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
> ]
>
> Bene updated XERCESJ-1382:
> --------------------------
>
> Attachment: xerces_performance_problem.xml
> xerces_performance_problem.png
>
> xerces_performance_problem.xml is the XML document which takes too long to
> parse / validate; xerces_performance_problem.png shows the JRat Performance
> analysis, which directs to org.apache.xerces.dom.CharacterDataImpl appendData
>
>
>> Performance problem in org.apache.xerces.dom.CharacterDataImpl appendData
>> -------------------------------------------------------------------------
>>
>> Key: XERCESJ-1382
>> URL: https://issues.apache.org/jira/browse/XERCESJ-1382
>> Project: Xerces2-J
>> Issue Type: Bug
>> Components: DOM (Level 3 Core)
>> Affects Versions: 2.6.0, 2.9.1
>> Environment: Windows XP SP2; JRE 1.6.0_13; Xerces2 Java Parser 2.9.1
>> Release (Xerces-J-bin.2.9.1.zip)
>> Reporter: Bene
>> Priority: Critical
>> Attachments: xerces_performance_problem.png,
>> xerces_performance_problem.xml
>>
>>
>> It takes too long to parse a large XML Document, if the document contains
>> CDATA sections, which contain embedded XML.
>> The problem initially occured with Xerces 2.6.0, where it took about 30
>> seconds !!! to parse an XML document with about 250 KB.
>> So we upgraded to Xerces 2.9.1, which improves parse time to about 5
>> seconds. Unfortunately this is still much too slow!
>> I tried to find similar bug reports and there are many:
>> XERCESJ-102
>> XERCESJ-1268
>> XALANJ-2398
>> Unfortunately the issue is still not fixed, so I decided to create this
>> report.
>
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