>> How do you handle entities in the XML ?

This code handles entities just fine as long as they dont end in ".dtd"




 	if( systemId.toLowerCase().endsWith(".dtd"))
                return new InputSource( new NullInputStream());
            else
                *return super.resolveEntity(publicId, systemId);*





David A. Lee
dlee@c...  
http://www.calldei.com
http://www.xmlsh.org
812-482-5224



Andrew Welch wrote:
> How do you handle entities in the XML ?
>
>
> 2009/9/3 David A. Lee <dlee@c...>:
>   
>> I solved this problem in a different that is less destructive.  This also
>> works to replace a DTD with a different one or to force validation on a
>> schema even if a non-existant DTD is specified.
>>
>> This particular implementation  requires using the SAXParser but I belive
>> the idea would work with other parsers that provide similar functionality,
>> namely an override of "resolveEntity".  The key trick is to resolve all
>> DTD's with a "NullInputStream" ( these are trivial to write so I wont supply
>> the code here)
>> An empty DTD file validates any XML (atleast it does in my tests).
>>
>> Here's the snippet
>>
>>
>>     private class ValidatorHandler extends DefaultHandler {
>>     ..... // other methods as needed
>>         @Override
>>         public InputSource resolveEntity(String publicId, String systemId)
>> throws IOException,
>>                 SAXException {
>>
>>             if( systemId.toLowerCase().endsWith(".dtd"))
>>                 return new InputSource( new NullInputStream());
>>             else
>>                 return super.resolveEntity(publicId, systemId);
>>         }
>>      }
>>
>>
>>
>>     SAXParserFactory f = SAXParserFactory.newInstance();
>>     .... setup the factory
>>
>>
>>
>>         SAXParser parser = f.newSAXParser();
>>        ... setup the parser
>>
>>
>>
>>         parser.parse(xml, new ValidatorHandler());
>>
>>
>>
>>
>>
>>
>>
>>
>> David A. Lee
>> dlee@c...
>> http://www.calldei.com
>> http://www.xmlsh.org
>> 812-482-5224
>>
>> Mike Sokolov wrote:
>>
>> After all the discussion about "What is data?" I don't know if this list is
>> the place to discuss actual details of implementation, but please feel free
>> to send me elsewhere if you can think of a better venue.
>>
>> I have a need to handle XML that references a non-existent DTD.  The DTD is
>> irrelevant to the actual processing of the XML, and isn't available
>> anywhere, but it is declared in in the DOCTYPE.  I'm sure many of you have
>> encountered this situation: it's practically the norm, in my experience.
>>
>> After years of dealing with this inherently unsatisfactory situation in a
>> variety of ways, I came up with a new one that I am liking at the moment,
>> which is to insert a Stream into a Java XML processing stack that strips out
>> the prolog of the XML document before handing it off to a parser.  This has
>> the nice property that it doesn't require modifications to the stored XML
>> files.  It loses PIs and comments and the XML decl, but I can live with
>> that.
>>
>> My question is twofold:
>>
>> 1) does the following code snippet actually do what it is claiming to?  Does
>> anybody see any obvious mistakes?  My knowledge of the format of DOCTYPE
>> decls and so on is somewhat limited.  I read the spec and this seems to work
>> on the examples I have, but I suspect there are some cases I'm not handling.
>>
>> 2) Is there a better approach?  Existing code to do the same thing?  Some
>> way to tell parsers to ignore the DOCTYPE (even though that seems to run
>> counter to the spec)?
>>
>> Thanks for your attention...
>>
>> -Mike Sokolov
>>
>>    /**
>>     * An InputStream for XML that strips off the prolog of an XML
>>     * document.  The idea is to avoid having to prevent parsers from
>> attempting
>>     * to process an external DTD.
>>     *
>>     * @author sokolov
>>     *
>>     */
>>    class XmlNoPrologInputStream extends PushbackInputStream {
>>               XmlNoPrologInputStream (InputStream base) throws IOException {
>>            super (base, 2);
>>            int c;
>>            while ((c = read()) >= 0) {
>>                if (c == '<') {
>>                    int c1 = read();
>>                    if (c1 < 0) {
>>                        // ill-formed
>>                        reset();
>>                        return;
>>                    }
>>                    // XML declaration, PI, comment or DOCTYPE
>>                    if (c1 == '?' || c1 == '!')
>>                        continue;
>>                    // must be the start of the document: arrange to begin
>>                    // reading here
>>                    unread(c1);
>>                    unread(c);
>>                    return;
>>                }
>>            }
>>        }
>>
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>>     
>
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