XOM API for Processing XML with Java

[Wolfgang Hoschek <whoschek AT lbl.gov>]

Question: Would it perhaps be better to have static Builder.create  
methods instead of constructors?

That way one would gain a little flexibility in how/what kind of  
builder is returned. For example,
one could (in some later XOM release) conceivably return a builder from  
a thread local pool or similar (recognizing that constructing the  
underlying XMLReader of a Builder is an extremely expensive operation;  
takes 2 milliseconds or more).

Background: currently i'm using something like this to reuse builders  
for lots of smallish XML files in a thread-safe way (which is not quite  
general enough for everyones needs, but should outline the overall  
idea):

import nu.xom.Builder;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;

/**
 * A pool holding one XOM Builder per thread.
 */
public class ThreadLocalBuilder extends ThreadLocal {
        
        private boolean isValidating;
        private String namespace = null;
        private String schema = null;
        
        public ThreadLocalBuilder() {
                isValidating = false;
        }

        public ThreadLocalBuilder(String namespace, String schema) {
                isValidating = true;
                this.namespace = namespace;
                this.schema = schema;
        }

        public Builder getBuilder() {
                return (Builder) get();
        }
        
        protected Object initialValue() {
                if (! isValidating) return new Builder();

                try {
                        // make xerces cache the parsed schema grammar for 
better performance
			// 
System.setProperty("org.apache.xerces.xni.parser.XMLParserConfiguration" 
,
                        //      
"org.apache.xerces.parsers.XMLGrammarCachingConfiguration");
                        
			XMLReader parser =  
XMLReaderFactory.createXMLReader("org.apache.xerces.parsers.SAXParser");
                        
                        
//parser.setFeature("http://xml.org/sax/features/validation";, true);
			parser.setFeature("http://apache.org/xml/features/validation/ 
schema", true);
                        
                        if (namespace != null && schema != null) {
                                parser.setProperty(
                                        
"http://apache.org/xml/properties/schema/external-schemaLocation";,
                                        namespace + " " + schema);
                        }
                        else if (schema != null) {
                                parser.setProperty(
					"http://apache.org/xml/properties/schema/external- 
noNamespaceSchemaLocation",
                                        schema);
                        }
                        
                        return new Builder(parser, true);
                } catch (SAXException e) {
                        throw new RuntimeException(e);
                }
        }

}


-----------------------------------------------------------------------
Wolfgang Hoschek                  |   email: whoschek AT lbl.gov
Distributed Systems Department    |   phone: (415)-533-7610
Berkeley Laboratory               |   http://dsd.lbl.gov/~hoschek/
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