Hi again,
Out of interest - what's the reason for not setting the system
property after doing the META-INF search? At the moment every jar
file gets examined every time an XMLReader is created - is there a
situation where users want different results from subsequent calls to
createXMLReader("...") controlled purely by the classpath?
With that system property set, it's really fast to create XMLReaders...
On 12 November 2013 19:18, Michael Glavassevich <[email protected]> wrote:
> Hi Andrew,
>
> Creating a new XML parser can be very expensive. The ClassLoader used to
> create the parser and its internal components might block or spend a long
> time searching its "classpath" for META-INF/services files. This is why
> it's generally a good idea to cache and reuse [1] XML parser instances.
>
> Thanks.
>
> [1]
> http://www.ibm.com/developerworks/xml/library/x-perfap2/index.html#reuse
>
> Michael Glavassevich
> XML Technologies and WAS Development
> IBM Toronto Lab
> E-mail: [email protected]
> E-mail: [email protected]
>
> Andrew Welch <[email protected]> wrote on 11/12/2013 07:48:47 AM:
>
>> Hi,
>>
>> A colleague was doing some performance testing and discovered some
>> contention at this line of my code:
>>
>> XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");
>>
>> ...which was surprising : ) He informed me it was doing a blocking
>> operation every time.
>>
>> Anyway, he went away and went through the Xerces source and found that
>> if the "org.apache.xerces.xni.parser.XMLParserConfiguration" system
>> property is not set it does indeed do a blocking operation (in
>> parsers.ObjectFactory)
>>
>> To demonstrate this, run the below code with and without the system
>> property set:
>>
>> public static void main(String... args) throws Exception {
>>
>> //System.setProperty
>> ("org.apache.xerces.xni.parser.XMLParserConfiguration",
>> // "org.apache.xerces.parsers.XIncludeParserConfiguration");
>>
>> long start = System.nanoTime();
>>
>> for (int i = 0; i <= 10000; i++) {
>> XMLReaderFactory.createXMLReader
>> ("org.apache.xerces.parsers.SAXParser");
>> }
>>
>> long end = System.nanoTime();
>> double millis = (end - start) * 1e-6;
>>
>> System.out.println(millis);
>>
>> }
>>
>> On my machine it consistently takes around ~2000ms without the system
>> property, and ~1300ms with.
>>
>> This is present in both 2.9 and 2.11 as far as I can see.
>>
>>
>>
>>
>> --
>> Andrew Welch
>> http://andrewjwelch.com
>>
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>
>
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--
Andrew Welch
http://andrewjwelch.com
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