When to use SAX

Java object properties stored in XML format.

queries that are formulated using some kind of text based query language (SOL, XQL, OQL).

result sets that are generated based on queries (this might include data in relational database tables encoded into XML).

So, machine generated data is information that you normally have to create data structures and classes in Java. A simple example is the address book, which contains information about persons, as shown in the diagram before. This address book XML file is not like a word processor document, rather it is a document that contains pure data, which has been encoded into text using XML.

When your data is of this kind, you have to create your own data structures and classes in order to manage, manipulate and persist this data. SAX allows you to quickly create a handier class, which can create instances of your object models based on the data stored in your XML documents. An example is a SAX document handler that reads an XML document that contains my address book and creates an AddressBook class that can be used to access this information. The address book XML document contains person elements, which contain name and e mail elements. My AddressBook object model contains the following classes:

AddressBook class, which is a container for Person objects

Person class, which is a container for name and e mail String objects.

So my "SAX address book document handier" is responsible for turning person elements into Person objects, and then storing them all in an AddressBook object. This document handler turns the name and email elements into String objects.

The SAX document handler you write does element to object mapping. If your information is structured in a way that makes it easy to create this mapping, you should use the SAX API. On the other hand, if your data is much better represented as a tree then you should use DOM.

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