Our series takes a look at Chapter 11: XML Tools for Information Appliances.

MinML

MinML, presumably standing for minimal XML, can be downloaded from http://www.wilson.co.uk/xml/minml.htm. It is the smallest parser reviewed in this book, and the fastest one mentioned in this chapter. It is also SAX 1.0 compliant, and consumes less memory than NanoXML.

However, it does not offer a pull parsing mechanism. Parsing is only available through the SAX 1.0 interface, which "pushes" events into your application code (see Push, Pull, and Object Model Parsing.)

After telling the parser to begin, the MinML calls back (or pushes) into your application code to notify you of parse events. This model forces your code to maintain state information within the callback class(es), and to evaluate that state at each event. This is less programmer-friendly than pull parsers like kXML and XPP, but it's hard to argue with MinML's raw speed. For benchmarks see http://www.extreme.indiana.edu/~aslom/exxp/. Perhaps MinML wouldn't be as fast if we account for the state information which application code must maintain that is maintained for us automatically by pull parsers.

Feature	Supported	Notes
Document validation	No	DTDs are read but ignored
Well-formed XML only	Yes	Throws org.xml.sax.SAXException if not well-formed
Mixed content	No	Throws org.xml.sax.SAXException
Entity expansion	No	Throws org.xml.sax.SAXException if predefined or general entities are used in an XML document. Parameter entities in the DTD are OK.
SAX	Yes, SAX 1.0
DOM	No
Comments	Ignored
Processing Instructions	Ignored
Namespaces	Indirectly	Prefixes aren't distinguished from local parts — <prefix:name> becomes an atomic element or attribute
Document Locator	No	Provides document line and column information
JAR size		15.3KB

As stated above, SAX 1.0 is implemented in its bare-bones state. Locales aren't supported. Warnings and errors aren't supported; all errors and warnings are reported as fatalerrors. Public and system identifiers aren't supported.

MinML provides no way to natively build and output documents: there is no object model, or element/node class from which to build documents

In true minimalist fashion, this package contains only one class — MinML. However, let's briefly look at it.

Class MinML
uk.co.wilson.xml

public class MinML extends java.lang.Object implements uk.org.xml.sax.Parser, uk.org.xml.sax.DocumentHandler, org.xml.sax.Locator, org.xml.sax.ErrorHandler

Although this is the only class in its package, it implements and uses many of the SAX 1.0 interfaces and classes. Those interfaces and classes must be distributed with MinML and should be in the CLASSPATH variable.

• Extending it with your own class and overriding the SAX methods in which you are interested
• Creating an instance of the class, calling setDocumentHandler() on the instance, and calling its parse() method with an org.xml.sax.InputSource object or a java.io.Reader object

You will notice that class MinML implements uk.org.xml.sax.Parser and uk.org.xml.sax.DocumentHandler instead of the org.xml.sax.Parser and org.xml.sax.DocumentHandler. These two interfaces actually just extend their SAX counterparts and override only three methods. It is by overriding these methods that MinML implements one of its unique features: sending output to a java.io.Writer object.

SAX's DocumentHandler interface has two methods, startElement() and startDocument(), both of which return void. The versions in uk.org.xml.sax.DocumentHandler, however, return a java.io.Writer. By overriding these methods in your application and returning a Writer, MinML will write character data to the Writer object instead of calling back the application's characters() method.