RE: load DTD in memory.

[Nicolas LEHUEN <nicolas.lehuen@ubicco.com>]

I didn't finish this mail, sorry :).

To implement a DTD catalog, you can use the same techniques that were use
top build the in-memory DTD cache, but things will get a little bit more
complicated, as you'll have to keep a persistent index of your cache in a
file. There are certainly already existing implementations of this ; have a
look at Norman Walsh's http://www.sun.com/software/xml/developers/resolver/
for example.

Another way of improving performances, is simply to switch off DTD
validation. This way you won't ever load DTDs in memory, and without
validation the parsing process is much faster, but less sure. This is done
by calling setFeature("http://xml.org/sax/features/validation",false) on the
SAX parser or the DocumentBuilder.

Regards,
Nicolas

-----Message d'origine-----
De : Nicolas LEHUEN 
Envoyé : vendredi 7 septembre 2001 12:36
À : 'Giuseppe Sarno'; 'xml-dev@lists.xml.org'
Objet : RE: load DTD in memory.


Well if you are loading many documents with the same DTD, you'll have
improvements. If your documents DTDs are all differents, then you should
consider having a persistent DTD cache, i.e. storing DTD as files and
associating these files to their PUBLIC id. This is a kind of DTD catalog.

-----Message d'origine-----
De : Giuseppe Sarno [mailto:gsarno@nortelnetworks.com]
Envoyé : vendredi 7 septembre 2001 12:31
À : Nicolas LEHUEN; 'xml-dev@lists.xml.org'
Objet : RE: load DTD in memory.


Hi I implemented this,
but apparently I didn't get any improvements.
I was expecting to be very quick.
Is it possible ?

cheers.
-----Original Message-----
From: Nicolas LEHUEN [mailto:nicolas.lehuen@ubicco.com]
Sent: 06 September 2001 16:10
To: Sarno, Giuseppe [MAIFP:GM12:EXCH]; 'xml-dev@lists.xml.org'
Subject: RE: load DTD in memory.


Oops sorry I wrote the code directly in the mail, without compiling it :).
You should have read (and corrected) :

InputStream isP=urlP.openStream();

Do not hesitate to have a look at the Javadoc to solve such problems. That's
a must if you want to achieve fast development in Java : always have your
Javadoc at hand.

Regards,
Nicolas
-----Message d'origine-----
De : Giuseppe Sarno [mailto:gsarno@nortelnetworks.com]
Envoyé : jeudi 6 septembre 2001 11:33
À : Nicolas LEHUEN; 'xml-dev@lists.xml.org'
Objet : RE: load DTD in memory.


hi I'm getting error on 
InputStream isP=urlP.openConnection(); 
Incompatible type for declaration. Can't convert java.net.URLConnection to
java.io.InputStream. 
                        InputStream isP=urlP.openConnection(); 
                                    ^ 
1 error 
what should i do for that ? 
cheers. 
-----Original Message----- 
From: Nicolas LEHUEN [mailto:nicolas.lehuen@ubicco.com] 
Sent: 05 September 2001 14:09 
To: Sarno, Giuseppe [MAIFP:GM12:EXCH]; 'xml-dev@lists.xml.org' 
Subject: RE: load DTD in memory. 


Well, here is a sample class for a in-memory entity cache (it will therefore

cache DTDs). It is a dumb cache, because if the original DTD changes, the 
cache is not refreshed, but for many cases it is sufficient. We have 
implemented a much more flexible caching framework, but here it's out of 
scope. 
import java.net.*; 
import java.util.*; 
import org.xml.sax.*; 
public class DTDMemoryCache implements EntityResolver { 
    private Map cache=new HashMap(); 
    // Remember to handle synchronization issues !! 
    // A dumb but easy implementation would synchronize the whole 
    // resolveEntity method 
    public synchronized InputSource resolveEntity(String publicIdP,String 
systemIdP) throws SAXException { 
        // The PUBLIC id is the key to our cache 
        byte[] resultP=cache.get(publicIdP); 
        if(resultP==null) { 
            try { 
                        // The SYSTEM id is the URL used to fetch the entity

                        URL urlP=new URL(systemIdP); 
                        InputStream isP=urlP.openConnection(); 
                        ByteArrayOutputStream baosP=new 
ByteArrayOutputStream(); 
                        // We copy the input stream into the output stream 
                        // Fast buffer implementation 
                        // I could have used BufferInputStream and 
OutputStream 
                        // But it's much slower 
                        int readP; 
                        byte[] bufferP=new byte[1024]; 
                        while((readP=isP.read(bufferP))>-1) { 
                                baosP.write(bufferP,0,readP); 
                        } 
                        resultP=baosP.toByteArray(); 
                        
                        // We store the result in the cache. 
                        cache.put(publicIdP,resultP); 
            } 
            catch(Exception eP) { 
                throw new SAXException(eP); 
            } 
        } 
        return new InputSource(new ByteArrayInputStream(resultP)); 
    } 
} 
Now, how to install this EntityResolver ? Both the org.xml.sax.Parser and 
the javax.xml.parsers.DocumentBuilder have a setEntityResolver() method that

enables you to install your own EntotyResolver before parsing your 
documents. 
Regards, 
Nicolas 
-----Message d'origine----- 
De : Giuseppe Sarno [mailto:gsarno@nortelnetworks.com] 
Envoyé : mercredi 5 septembre 2001 14:47 
À : Nicolas LEHUEN; 'xml-dev@lists.xml.org' 
Objet : RE: load DTD in memory. 


hi, 
thanks for your answer, 
but could you please tell me more on how to do it since the API doc doesn't 
explain it very well. 
cheers. 
-----Original Message----- 
From: Nicolas LEHUEN [mailto:nicolas.lehuen@ubicco.com] 
Sent: 05 September 2001 13:26 
To: Sarno, Giuseppe [MAIFP:GM12:EXCH]; 'xml-dev@lists.xml.org' 
Subject: RE: load DTD in memory. 


To cache DTDs the easiest thing to do with SAX is to implement your own 
EntityResolver. This way you'll be able to cache locally or in memory all 
entities, amongst them the DTDs. 
Regards, 
Nicolas 
-----Message d'origine----- 
De : Giuseppe Sarno [mailto:gsarno@nortelnetworks.com] 
Envoyé : mercredi 5 septembre 2001 13:56 
À : xml-dev@lists.xml.org 
Objet : load DTD in memory. 


Hi , 
I was wondering , 
in case is needed to parse a lot of XML docs , is it possible to 
load the DTD or Schema one in memory and always reuse it instead of 
reloading it for each Doc validation ? 
cheers. 
--------------InterScan_NT_MIME_Boundary-- 
--------------InterScan_NT_MIME_Boundary-- 
--------------InterScan_NT_MIME_Boundary--
--------------InterScan_NT_MIME_Boundary--