Question

I came across two different codes for parsing a file with StAX. A quick googling told me that there are 2 ways to parse : using cursor API and using iterator API. Please tell me the difference between the two and which one is easier to use from developer point of view.

Answer 1

You’re most likely to find the answer in the StAX API sections within the Java Web Services Developer Pack tutorial or Java EE 5 tutorial. Both of them contain the same information that I am reproducing below:

Comparing Cursor and Iterator APIs

Before choosing between the cursor and
iterator APIs, you should note a few
things that you can do with the
iterator API that you cannot do with
cursor API:

• Objects created from the XMLEvent subclasses are immutable, and can be
  used in arrays, lists, and maps, and
  can be passed through your
  applications even after the parser has
  moved on to subsequent events.

• You can create subtypes of XMLEvent that are either completely
  new information items or extensions of
  existing items but with additional
  methods.

• You can add and remove events from an XML event stream in much simpler
  ways than with the cursor API.

Similarly, keep some general
recommendations in mind when making
your choice:

• If you are programming for a particularly memory-constrained
  environment, like J2ME, you can make
  smaller, more efficient code with the
  cursor API.

• If performance is your highest priority–for example, when creating
  low-level libraries or
  infrastructure–the cursor API is more
  efficient.

• If you want to create XML processing pipelines, use the iterator
  API.

• If you want to modify the event stream, use the iterator API.

• If you want to your application to be able to handle pluggable processing
  of the event stream, use the iterator
  API.

• In general, if you do not have a strong preference one way or the
  other, using the iterator API is
  recommended because it is more
  flexible and extensible, thereby
  “future-proofing” your applications.

The iterator API although recommended is slower than the cursor API, as the cursor does not need to remember the previous nodes that it had parsed; it provides forward-only parsing of XML documents and does not have the overhead of construction of XMLEvent objects. Apparently, a benchmark has indicated that SAX might turn out to be better at parsing large documents compared to StAX; you might want to verify if you can reproduce the results of the benchmark for your data-sets.