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9.4. Gotcha!

The API chapters wouldn't be complete without letting you know about some problems that I frequently run into or that I'm asked about. Hopefully they'll help save you some time, and maybe make your code more bug-proof. Read on, and see where JAXP catches folks these days.

9.4.2. Features on Factories, Properties on Parsers

One common mistake is to mix up factories and properties in the JAXP world. The best way to remember the correct application is to memorize the phrase "features on factories, properties on parsers." You would be amazed at the number of mails I get insisting that the sender has a "corrupt" version of JAXP, because the following code won't compile:

SAXParserFactory factory = SAXParserFactory.newInstance( );

Of course, this is a property, and therefore must be set on a SAXParser instance, not a SAXParserFactory instance. The reverse, of course, holds true for setting features on parsers:

SAXParser parser = factory.newSAXParser( );
parser.setFeature("http://xml.org/sax/features/namespaces", true);

In either case, it is user error, not a strange download problem where all but a few methods came across OK (I generally refer these people to some good books on I/O). This is also a good case of the Javadocs not being used when they should. I'm a firm believer in the value of Javadoc.

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