Java XPath (Apache JAXP implementation) performance

by

I have debugged and profiled my test-case and Xalan/JAXP in general. I managed to identify the big major problem in 

org.apache.xml.dtm.ObjectFactory.lookUpFactoryClassName()

It can be seen that every one of the 10k test XPath evaluations led to the classloader trying to lookup the DTMManager instance in some sort of default configuration. This configuration is not loaded into memory but accessed every time. Furthermore, this access seems to be protected by a lock on the ObjectFactory.class itself. When the access fails (by default), then the configuration is loaded from the xalan.jar file’s

META-INF/service/org.apache.xml.dtm.DTMManager

configuration file. Every time!:

JProfiler profiling results

Fortunately, this behaviour can be overridden by specifying a JVM parameter like this:

-Dorg.apache.xml.dtm.DTMManager=
  org.apache.xml.dtm.ref.DTMManagerDefault

or

-Dcom.sun.org.apache.xml.internal.dtm.DTMManager=
  com.sun.org.apache.xml.internal.dtm.ref.DTMManagerDefault

The above works, as this will allow to bypass the expensive work in lookUpFactoryClassName() if the factory class name is the default anyway:

// Code from com.sun.org.apache.xml.internal.dtm.ObjectFactory
static String lookUpFactoryClassName(String factoryId,
                                     String propertiesFilename,
                                     String fallbackClassName) {
  SecuritySupport ss = SecuritySupport.getInstance();

  try {
    String systemProp = ss.getSystemProperty(factoryId);
    if (systemProp != null) { 

      // Return early from the method
      return systemProp;
    }
  } catch (SecurityException se) {
  }

  // [...] "Heavy" operations later

So here’s a performance improvement overview for 10k consecutive XPath evaluations of //SomeNodeName against a 90k XML file (measured with System.nanoTime():

measured library        : Xalan 2.7.0 | Xalan 2.7.1 | Saxon-HE 9.3 | jaxen 1.1.3
--------------------------------------------------------------------------------
without optimisation    :     10400ms |      4717ms |              |     25500ms
reusing XPathFactory    :      5995ms |      2829ms |              |
reusing XPath           :      5900ms |      2890ms |              |
reusing XPathExpression :      5800ms |      2915ms |      16000ms |     25000ms
adding the JVM param    :      1163ms |       761ms |        n/a   |

note that the benchmark was a very primitive one. it may well be that your own benchmark will show that saxon outperforms xalan

I have filed this as a bug to the Xalan guys at Apache:

https://issues.apache.org/jira/browse/XALANJ-2540

More Related Contents:

  1. Why is printing “B” dramatically slower than printing “#”?
  2. Difference between declaring variables before or in loop?
  3. Does use of final keyword in Java improve the performance?
  4. Why is creating a Thread said to be expensive?
  5. Is there a performance difference between a for loop and a for-each loop?
  6. .toArray(new MyClass[0]) or .toArray(new MyClass[myList.size()])?
  7. Swing animation running extremely slow
  8. Java lambdas 20 times slower than anonymous classes
  9. System.currentTimeMillis() vs. new Date() vs. Calendar.getInstance().getTime()
  10. Faster alternatives to Java’s reflection [closed]
  11. Java: what’s the big-O time of declaring an array of size n?
  12. Calling getters on an object vs. storing it as a local variable (memory footprint, performance)
  13. Performance difference between Java 8 lambdas and anonymous inner classes
  14. Best practice for passing many arguments to method?
  15. Docx to Pdf Converter in java
  16. how to make log4j to write to the console as well
  17. What is the time complexity of HashMap.containsKey() in java?
  18. Most efficient Java primitive collections library [closed]
  19. fastest (low latency) method for Inter Process Communication between Java and C/C++
  20. Know of any Java garbage collection log analysis tools? [closed]
  21. What is the fastest Java collection with the basic functionality of a Queue?
  22. Default XML namespace, JDOM, and XPath
  23. Which “if” construct is faster – statement or ternary operator?
  24. What is the quantitative overhead of making a JNI call?
  25. Java split String performances
  26. What is the Metadata GC Threshold and how do I tune it?
  27. ArrayList vs. Vectors in Java if thread safety isn’t a concern
  28. Is using java Map.containsKey() redundant when using map.get()
  29. Performance of WebView in JavaFX
  30. What GC parameters is a JVM running with?

Leave a Comment