org.xml.sax
Interface EntityResolver
- EntityResolver2
- DefaultHandler, DefaultHandler2, HandlerBase, PersistenceParser, Resolver, XCat, XMLFilterImpl
Basic interface for resolving entities.
This module, both source code and documentation, is in the
Public Domain, and comes with NO WARRANTY.
See http://www.saxproject.org
for further information.
If a SAX application needs to implement customized handling
for external entities, it must implement this interface and
register an instance with the SAX driver using the
setEntityResolver
method.
The XML reader will then allow the application to intercept any
external entities (including the external DTD subset and external
parameter entities, if any) before including them.
Many SAX applications will not need to implement this interface,
but it will be especially useful for applications that build
XML documents from databases or other specialised input sources,
or for applications that use URI types other than URLs.
The following resolver would provide the application
with a special character stream for the entity with the system
identifier "http://www.myhost.com/today":
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
public class MyResolver implements EntityResolver {
public InputSource resolveEntity (String publicId, String systemId)
{
if (systemId.equals("http://www.myhost.com/today")) {
// return a special input source
MyReader reader = new MyReader();
return new InputSource(reader);
} else {
// use the default behaviour
return null;
}
}
}
The application can also use this interface to redirect system
identifiers to local URIs or to look up replacements in a catalog
(possibly by using the public identifier).
resolveEntity
public abstract InputSource resolveEntity(String publicId,
String systemId)
throws SAXException,
IOException Allow the application to resolve external entities.
The parser will call this method before opening any external
entity except the top-level document entity. Such entities include
the external DTD subset and external parameter entities referenced
within the DTD (in either case, only if the parser reads external
parameter entities), and external general entities referenced
within the document element (if the parser reads external general
entities). The application may request that the parser locate
the entity itself, that it use an alternative URI, or that it
use data provided by the application (as a character or byte
input stream).
Application writers can use this method to redirect external
system identifiers to secure and/or local URIs, to look up
public identifiers in a catalogue, or to read an entity from a
database or other input source (including, for example, a dialog
box). Neither XML nor SAX specifies a preferred policy for using
public or system IDs to resolve resources. However, SAX specifies
how to interpret any InputSource returned by this method, and that
if none is returned, then the system ID will be dereferenced as
a URL.
If the system identifier is a URL, the SAX parser must
resolve it fully before reporting it to the application.
publicId - The public identifier of the external entity
being referenced, or null if none was supplied.systemId - The system identifier of the external entity
being referenced.
- An InputSource object describing the new input source,
or null to request that the parser open a regular
URI connection to the system identifier.
SAXException - Any SAX exception, possibly
wrapping another exception.IOException - A Java-specific IO exception,
possibly the result of creating a new InputStream
or Reader for the InputSource.