You should register an error handler with the parser by supplying
a class which implements the org.xml.sax.ErrorHandler
interface. This is true regardless of whether your parser is a
DOM based or SAX based parser.
You can register an error handler on a DocumentBuilder
created using JAXP like this:
How can I control the way that entities are represented in the DOM?
The DOM Level 3 feature create-entity-ref-nodes (or corresponding Xerces http://apache.org/xml/features/dom/create-entity-ref-nodes feature)
control how entities appear in the DOM tree. When one of those features
is set to true (the default), an occurance of an entity reference
in the XML document will be represented by a subtree with an
EntityReference node at the root whose children represent the
entity expansion.
If the feature is false, an entity reference in the XML document
is represented by only the nodes that represent the entity
expansion.
In either case, the entity expansion will be a DOM tree
representing the structure of the entity expansion, not a text
node containing the entity expansion as text.
Why does "non-validating" not mean "well-formedness
checking only"?
Using a "non-validating" parser does not mean that
only well-formedness checking is done! There are still many
things that the XML specification requires of the parser,
including entity substitution, defaulting of attribute values,
and attribute normalization.
This table describes what "non-validating" really
means for Xerces-J parsers. In this table, "no DTD"
means no internal or external DTD subset is present.
non-validating parsers
validating parsers
DTD present
no DTD
DTD present
no DTD
DTD is read
Yes
No
Yes
Error
entity substitution
Yes
No
Yes
Error
defaulting of attributes
Yes
No
Yes
Error
attribute normalization
Yes
No
Yes
Error
checking against model
No
No
Yes
Error
How do I associate my own data with a node in the DOM tree?
The class org.apache.xerces.dom.NodeImpl provides a
void setUserData(Object o) and an Object
getUserData() method that you can use to attach any object
to a node in the DOM tree.
Beware that you should try and remove references to your data on
nodes you no longer use (by calling setUserData(null),
or these nodes will not be garbage collected until the entire
document is garbage collected.
How do I more efficiently parse several documents sharing a
common DTD?
DTDs are not currently cached by the parser. The common DTD,
since it is specified in each XML document, will be re-parsed
once for each document.
However, there are things that you can do now, to make the
process of reading DTD's more efficient:
keep your DTD and DTD references local
use internal DTD subsets, if possible
load files from server to local client before parsing
Cache document files into a local client cache. You should do an
HTTP header request to check whether the document has changed,
before accessing it over the network.
Do not reference an external DTD or internal DTD subset at all.
In this case, no DTD will be read.
Use a custom EntityResolver and keep common
DTDs in a memory buffer.