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Java Project X
Version: Early Access 2
This document contains notes that may help you use this library
Please feel free to send problem reports,
questions, and other feedback to the feedback alias,
With respect to new feature requests, please keep in mind that we
want to see packages built on top of this core for most features.
The core API is intended to facilitate such a layered architecture
for value-added products that leverage XML.
Changes since EA 1
- DOM support conforms to the W3C recommendation, not
the proposed recommendation. Changes include renaming the
"Attribute" interface to "Attr" to fix a conflict with a
reserved word in OMG-IDL.
- DOM space and time performance was improved.
- Most classes in the com.sun.xml.tree package
are now private. There are new interfaces. Some of the APIs
- In the com.sun.xml.parser package, the
static methods for checking character and name types have
been moved out of the parser class for clarity. New
interfaces have been defined, for better DOM support.
- There is now an ElementFactory interface which
supports namespace-aware creation of elements. You can have
two element types, distinguished only by namespace URIs, which
instantiate as different XML Beans. SimpleElementFactory
provides a table-driven implementation of this functionality.
- Minor bugfixes have been implemented, including implementing
some missing DOM functionality.
- New examples have been provided, including one using XML
with HTTP for messaging.
- The parsers conform to the W3C's
- The parse tree supports the XML (core) part of W3C's
DOM Level 1
- In combination, the two also support the current W3C
XML Namespaces proposed recommendation.
- The parser supports the SAX
- The entity resolution used within the parser normally
conforms to the IETF's RFC 2376 registration for XML-related
MIME content types. This can be overridden as required.
(See below; overriding may be needed since many web servers do
not conform to that specification, and report incorrect character
set encoding information.)
- There are two separate parsers, sharing almost all the same
code. The validating parser is slightly slower since it performs
additional error checking.
- Because SAX specifies the default error handling to be that
validation errors are ignored, the validating parser normally accepts
invalid documents (when they are are well formed). To reject such
documents, configure an implementation of
error() method which throws its argument.
- Both parsers normally read all external entities, and so their
behavior is all but completely defined by the XML specification. An
exception is that for valid standalone documents you may enable a
"fast standalone" mode, which skips external parts of the DTD if
validation is not being performed.
- Please let us know about any diagnostics produced by the
parser which are misleading or confusing.
- If you are working with text encodings other than UTF-8 and
UTF-16, you should put a text declaration at the very beginning of
all your XML documents (including DTDs). If you don't do this, the
parser will not be able to determine the encoding being used, and
will probably be unable to parse your document. A text declaration
<?xml version='1.0' encoding='euc-jp'?> says
that the document uses the "euc-jp" encoding.
- The parser currently reports warnings, rather than errors,
in cases where the declared and actual text encodings don't match.
It gives those same warnings in the common case where the encoding
name used internally to Java is not the one used in the document.
If the declared encoding is truly an error, you'll usually see other
errors (not warnings) being reported by the parser.
- Currently, many web servers report incorrect MIME types for
XML documents using non-ASCII encodings. Such situations are
indicated through the warning noted above, and are often followed
by other errors (not warnings). You may work around such web server
problems by disabling MIME typing support by using a properly
configured com.sun.xml.parser.Resolver, disabling
the use of MIME typing information.
- The parser currently does not report an error for content
models which are not deterministic. Accordingly it may not behave
well when given data which matches an "ambiguous" content model
such as ((a,b)|(a,c)). DTDs with such models are in
error, and must be restructured to be unambiguous. (In the example,
(a,(b|c)) is an equivalent legal content model.)
- Conforming to the XML specification, the parser reports all
whitespace to the DOM even if it's meaningless. Many applications
do not want to see such whitespace. You can remove it by invoking
the ElementNode.normalize method, which merges adjacent text
nodes and also canonicalizes adjacent whitespace into a single space
(unless the xml:space="preserve" attribute prevents that).
- Currently, attribute nodes may not have children. Access their
values as strings, instead of enumerating children.
- Currently, when documents are cloned the clone will not have a
clone of the associated ElementFactory or DocumentType.
- To get full XML namespace support, you must use one of the Sun
XML parsers and pass it to the XmlDocumentBuilder.setParser
method. Otherwise names with colons aren't constrained as required
during parsing, so various document errors will be ignored.
- The in-memory representation of text nodes has not been tuned
to be efficient with respect to space utilization.
- We're seeking feedback on "XML Beans". What sorts of things
have you successfully used them for? What sorts of things did you
have trouble with?
- We expect to make source code available in a later version,
for use as reference code (as is done for the Java core classes).
- Similarly, we expect to permit no-fee
commercial use in a later version
when functionality and APIs have stabilized.