Insert a doctype into an XML document (Java/ SAX)
- by Thom Nichols
Imagine you have an XML document and imagine you have the DTD but the document itself doesn't actually specify a DOCTYPE ... How would you insert the DOCTYPE declaration, preferably by specifying it on the parser (similar to how you can set the schema for a document that will be parsed) or by inserting the necessary SAX events via an XMLFilter or the like?
I've found many references to EntityResolver, but that is what's invoked once a DOCTYPE is found during parsing and it's used to point to a local DTD file. EntityResolver2 appears to have what I'm looking for but I haven't found any examples of usage.
This is the closest I've come thus far: (code is Groovy, but close enough that you should be able to understand it...)
import org.xml.sax.*
import org.xml.sax.ext.*
import org.xml.sax.helpers.*
class XmlFilter extends XMLFilterImpl {
public XmlFilter( XMLReader reader ) { super(reader) }
@Override public void startDocument() {
super.startDocument()
super.resolveEntity( null,
'file:///./entity.dtd')
println "filter startDocument"
}
}
class MyHandler extends DefaultHandler2 {
public InputSource resolveEntity(String name, String publicId, String baseURI, String systemId) {
println "entity: $name, $publicId, $baseURI, $systemId"
return new InputSource(new StringReader('<!ENTITY asdf "¡">'))
}
}
def handler = new MyHandler()
def parser = XMLReaderFactory.createXMLReader()
parser.setFeature 'http://xml.org/sax/features/use-entity-resolver2', true
def filter = new XmlFilter( parser )
filter.setContentHandler( handler )
filter.setEntityResolver( handler )
filter.parse( new InputSource(new StringReader('''<?xml version="1.0" ?>
<test>one &asdf; two! ¡£¢</test>''')) );
I see resolveEntity called but still hit
org.xml.sax.SAXParseException: The entity "asdf" was referenced, but not declared.
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1231)
at org.xml.sax.helpers.XMLFilterImpl.parse(XMLFilterImpl.java:333)
I guess this is because there's no way to add SAX events that the parser knows about, I can only add events via a filter that's upstream from the parser which are passed along to the ContentHandler. So the document has to be valid going into the XMLReader. Any way around this? I know I can modify the raw stream to add a doctype or possibly do a transform to set a DTD... Any other options?
