Cart
|
[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: SAX: New Idea for Entity Resolution
James Clark writes:
> You could just have a class that encapsulates a structure with three
> members:
>
> - a CharacterStream
> - a ByteStream
> - a String
>
> At least one of the CharacterStream and ByteStream must be non-null. If
> the ByteStream is non-null the String can specify the encoding.
[Read on to the bottom for a large-ish design change.]
This implies, then, the following three interfaces:
public interface ByteStream {
public abstract int read ()
throws SAXException;
public abstract int read (byte b[], int start, int count)
throws SAXException;
}
public interface CharacterStream {
public abstract int read ()
throws SAXException;
public abstract int read (char ch[], int start, int count)
throws SAXException;
}
public class InputSource {
// For each variable, imagine a get/set pair instead...
public ByteStream byteStream;
public CharacterStream characterStream;
public String encoding;
}
The nice thing here is that all of these can live on separate systems
in a distributed environment: the InputSource can be a C-program on a
VAX, the CharacterStream can come a Python program running under alpha
Linux, and the parser can be running in Java on a Windows box. There
is no dependency on language- or system-specific features (except for
java.lang.String, which should be able to map predictably to other
languages).
Now, why not take this a step further?
public class InputSource {
// For each variable, imagine a get/set pair instead...
public String publicId;
public String systemId;
public ByteStream byteStream;
public CharacterStream characterStream;
public String encoding;
}
We'd have to define rules of precedence:
1) if there is a character stream, use it;
2) if there is no character stream but there is a byte stream, use the
byte stream;
3) if there is neither a character stream nor a byte stream but there
is a system identifier, open a connection to the system identifier;
4) if there is no character stream, byte stream, or system identifier,
throw an exception (or invoke the ErrorHandler).
Now, we can get away with only one parse() method in
org.xml.sax.Parser:
public abstract void parse (InputSource source)
throws Exception;
It might still be useful to keep two separate methods in
EntityResolver, though:
public interface EntityResolver
{
public String resolveSystemId (String publicId, String systemId)
throws SAXException;
public InputSource openEntity (String systemId)
throws Exception;
}
Comments?
All the best,
David
--
David Megginson ak117@f...
Microstar Software Ltd. dmeggins@m...
http://home.sprynet.com/sprynet/dmeggins/
xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i...
Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/
To (un)subscribe, mailto:majordomo@i... the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo@i... the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa@i...)
|
PURCHASE STYLUS STUDIO ONLINE TODAY!Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced! 
Download The World's Best XML IDE!Accelerate XML development with our award-winning XML IDE - Download a free trial today! Subscribe in XML format
|
|||||||||
