javax.xml.parsers.XmlDocumentParserFactory

[pramod talekar]

Hello,

I was trying to a parse a document and came across the following statement :

DocumentBuilderFactory uses the system property javax.xml.parsers.XmlDocumentParserFactory to find the class to load.

I tried to print this property and it printed "null".

I wonder if the property is null then how all this parsing process works.
or is it just my case that the above property is coming as null.

Another thing is that I printed all the properties using getProperties() but there is no such property exists with this name.

Please advise.

[ali Dada]

write your sample code here.

[pramod talekar]

No code as such.

I read it on the net.

	System.out.println(System.getProperty(" javax.xml.parsers.XmlDocumentParserFactory"));
		System.out.println(System.getProperties());
	

This is the output :-

{java.runtime.name=Java(TM) SE Runtime Environment,
 sun.boot.library.path=C:\Program Files\Java\jdk1.6.0_18\jre\bin,
 java.vm.version=16.0-b13,
 java.vm.vendor=Sun Microsystems Inc., java.vendor.url=http://java.sun.com/, path.separator=;, java.vm.name=Java HotSpot(TM) Client VM,
 file.encoding.pkg=sun.io,
 sun.java.launcher=SUN_STANDARD,
 user.country=US,
 sun.os.patch.level=Service Pack 3,
 java.vm.specification.name=Java Virtual Machine Specification,
 user.dir=D:\workspace1\Horstman,
 java.runtime.version=1.6.0_18-b07,
 java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment,
 java.endorsed.dirs=C:\Program Files\Java\jdk1.6.0_18\jre\lib\endorsed,
 os.arch=x86,
 java.io.tmpdir=C:\DOCUME~1\ptalek\LOCALS~1\Temp\, line.separator=
,
 java.vm.specification.vendor=Sun Microsystems Inc., user.variant=, os.name=Windows XP,
 sun.jnu.encoding=Cp1252,
 java.library.path=C:\Program Files\Java\jdk1.6.0_18\bin;.;C:\WINDOWS\Sun\Java\bin;C:\WINDOWS\system32;C:\WINDOWS;C:/Program Files/Java/jdk1.5.0_05/bin/../jre/bin/client;C:/Program Files/Java/jdk1.5.0_05/bin/../jre/bin;C:/Program Files/Java/jdk1.5.0_05/bin/../jre/lib/i386;C:\Perl\site\bin;C:\Perl\bin;C:\Program Files\Java\jdk1.5.0_05\bin;C:\Ant-bin\apache-ant-1.8.2\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program Files\TortoiseSVN\bin;D:\MySql 5.5\bin;D:\derby\bin;D:\Junit\junit4.9b2\junit-4.9b2.jar;D:\Junit\junit4.9b2\junit-4.9b2-src.jar;D:\Junit\junit4.9b2\junit-dep-4.9b2.jar;;C:\Documents and Settings\ptalek;, java.specification.name=Java Platform API Specification,
 java.class.version=50.0,
 sun.management.compiler=HotSpot Client Compiler,
 os.version=5.1,
 user.home=C:\Documents and Settings\ptalek,
 user.timezone=, java.awt.printerjob=sun.awt.windows.WPrinterJob,
 file.encoding=Cp1252,
 java.specification.version=1.6,
 java.class.path=D:\workspace1\Horstman\bin,
 user.name=ptalek,
 java.vm.specification.version=1.0,
 java.home=C:\Program Files\Java\jdk1.6.0_18\jre,
 sun.arch.data.model=32,
 user.language=en,
 java.specification.vendor=Sun Microsystems Inc., awt.toolkit=sun.awt.windows.WToolkit,
 java.vm.info=mixed mode,
 sharing,
 java.version=1.6.0_18,
 java.ext.dirs=C:\Program Files\Java\jdk1.6.0_18\jre\lib\ext;C:\WINDOWS\Sun\Java\lib\ext,
 sun.boot.class.path=C:\Program Files\Java\jdk1.6.0_18\jre\lib\resources.jar;C:\Program Files\Java\jdk1.6.0_18\jre\lib\rt.jar;C:\Program Files\Java\jdk1.6.0_18\jre\lib\sunrsasign.jar;C:\Program Files\Java\jdk1.6.0_18\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.6.0_18\jre\lib\jce.jar;C:\Program Files\Java\jdk1.6.0_18\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.6.0_18\jre\classes,
 java.vendor=Sun Microsystems Inc., file.separator=\, java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport.cgi,
 sun.io.unicode.encoding=UnicodeLittle,
 sun.cpu.endian=little,
 sun.desktop=windows,
 sun.cpu.isalist=pentium_pro+mmx pentium_pro pentium+mmx pentium i486 i386 i86}

[John Jai]

Is the factory instance created like below or otherwise?

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

[Minh Nam]

pramod talekar wrote:Hello,

I was trying to a parse a document and came across the following statement :

DocumentBuilderFactory uses the system property javax.xml.parsers.XmlDocumentParserFactory to find the class to load.

I tried to print this property and it printed "null".

It is null means that there is no such property, dead simple.

[pramod talekar]

Hey Minh,

It is null means that there is no such property, dead simple.

If it is null, then all this shouldn't work, right ?

Yes, John, that's the way.

[Minh Nam]

pramod talekar wrote:

If it is null, then all this shouldn't work, right ?

Hi pramod,

What shouldn't work? You did not post the code that you are expecting to work, you posted just two System.out.println() statements.

[pramod talekar]

Ok, Here's the code :-

DocumentBuilderFactory dfb = DocumentBuilderFactory.newInstance();
		DocumentBuilder db = dfb.newDocumentBuilder();
		Document doc = db.newDocument();

If the said property is coming as null,
then the above lines should give error.

[Karthik Shiraly]

For such doubts, it's best to go through the JRE source code and understand. In this case, the relevant code is

    public static DocumentBuilderFactory newInstance() {
        try {
            return (DocumentBuilderFactory) FactoryFinder.find(
                /* The default property name according to the JAXP spec */
                "javax.xml.parsers.DocumentBuilderFactory",
                /* The fallback implementation class name */
                "com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl");
        } catch (FactoryFinder.ConfigurationError e) {
            throw new FactoryConfigurationError(e.getException(),
                                                e.getMessage());
        }

    }

It checks for the property. If it can't find, it falls back to the default Xerces parser bundled with Sun JRE.

[Maneesh Godbole]

pramod talekar wrote:
If the said property is coming as null,
then the above lines should give error.

From the API Docs

Obtain a new instance of a DocumentBuilderFactory. This static method creates a new factory instance. This method uses the following ordered lookup procedure to determine the DocumentBuilderFactory implementation class to load:

Use the javax.xml.parsers.DocumentBuilderFactory system property.

Use the properties file "lib/jaxp.properties" in the JRE directory. This configuration file is in standard java.util.Properties format and contains the fully qualified name of the implementation class with the key being the system property defined above. The jaxp.properties file is read only once by the JAXP implementation and it's values are then cached for future use. If the file does not exist when the first attempt is made to read from it, no further attempts are made to check for its existence. It is not possible to change the value of any property in jaxp.properties after it has been read for the first time.

Use the Services API (as detailed in the JAR specification), if available, to determine the classname. The Services API will look for a classname in the file META-INF/services/javax.xml.parsers.DocumentBuilderFactory in jars available to the runtime.

Platform default DocumentBuilderFactory instance.

[pramod talekar]

Thank you sir.