[jira] Commented: (AXIS2-565) Namespace vanishes using StAXOMBuilder

["Michael Krumpus (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AXIS2-565?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12500213 ] 

Michael Krumpus commented on AXIS2-565:
---------------------------------------

I know that the root problem here was closed, but I do think that the issue of unnecessarily *adding* numerous namespace declarations to a document is a problem.  Real web services may need to produce very long documents, and the network and CPU overhead of dealing with thousands of duplicate namespace declarations is significant.  (Yes, in the real world there may be thousands!).  

It looks to me like the problem is in StAXOMBuilder.processNamespaceData(OMElement element).  Here is the relevant part of the code:

        if (namespaceURI != null && namespaceURI.length() > 0) {
            OMNamespace namespace = node.findNamespace(namespaceURI, prefix);
            if (namespace == null || namespace.getPrefix() != prefix) {
                if (prefix == null || "".equals(prefix)) {
                    namespace = node.declareDefaultNamespace(namespaceURI);
                } else {
                    namespace = node.declareNamespace(namespaceURI, prefix);
                }
            } 
            node.setNamespaceWithNoFindInCurrentScope(namespace);
        }

The conditional
if (namespace == null || namespace.getPrefix() != prefix) {

says that if a namespace declaration is found somewhere in an ancestor element, the prefix of the local element be equal to the prefix of the namespace found.  Why?  Typically the local prefix returned from the StAX parser is "".  In this case, this code will declare a default namespace for the element instead of reusing the prefix already defined.  If the conditional is changed to:
if (namespace == null)

then the namespace found with findNamespace(uri, prefix) will be used and we get nice re-use of the existing prefix without declaring more namespaces (default or otherwise).  Is this the right change to make?  Will it break other things?  In the cases I've looked at, this change results in equivalent but less verbose documents.

Also, the API documentation for findNamespace(uri, prefix) states that either uri or prefix should be null, yet this code happily calls findNamespace with non-null values for each.  Is that a bug?


> Namespace vanishes using StAXOMBuilder
> --------------------------------------
>
>                 Key: AXIS2-565
>                 URL: https://issues.apache.org/jira/browse/AXIS2-565
>             Project: Axis 2.0 (Axis2)
>          Issue Type: Bug
>    Affects Versions: 0.95
>         Environment: Windows XP, Java 1.5
>            Reporter: Ant Grinyer
>            Assignee: Eran Chinthaka
>
> Below is the simple Junit test code which demonstrates the bug comments:
> package com.mytest;
> import org.apache.ws.commons.om.impl.builder.StAXOMBuilder;
> import org.apache.ws.commons.om.impl.llom.factory.OMXMLBuilderFactory;
> import org.apache.ws.commons.om.OMAbstractFactory;
> import org.jdom.Document;
> import org.jdom.output.XMLOutputter;
> import org.jdom.input.SAXBuilder;
> import javax.xml.stream.XMLStreamReader;
> import javax.xml.stream.XMLInputFactory;
> import java.io.StringReader;
> import junit.framework.TestCase;
> /**
>  * Test class to demonstrate namespace problem.
>  *
>  * Date: 11-Apr-2006
>  */
> public class Axis2Test extends TestCase {
>     public Axis2Test(String string) { super(string); }
>     protected void setUp() throws Exception { super.setUp(); }
>     protected void tearDown() throws Exception { super.tearDown(); }
>     public void testNameSpaces() {
>         StringBuffer sb = new StringBuffer();
>         sb.append("<root>");
>         sb.append("  <node>Some text</node>");
>         sb.append("  <node>More test</node>");
>         sb.append("  <items>");
>         sb.append("    <item shape=\"rectangle\" xmlns:col=\"urn:mycolor\"><col:color rgb=\"#FF0000\">red</col:color><name>My fine <b>item</b></name></item>");
>         sb.append("    <item shape=\"circle\" xmlns:col=\"urn:mycolor\"><col:color rgb=\"#0000FF\">blue</col:color><name>Something else</name></item>");
>         sb.append("  </items>");
>         sb.append("  <shapes>");
>         sb.append("    <shape>rectangle</shape>");
>         sb.append("    <shape>circle</shape>");
>         sb.append("    <shape basedOn=\"rectangle\">square</shape>");
>         sb.append("  </shapes>");
>         sb.append("</root>");
>         try {
>             // TRY WITH AXIS2 (loses xmlns:col="urn:mycolor" namespace on
>             // the <item shape="circle" xmlns:col="urn:mycolor"> element
>             XMLStreamReader parser = XMLInputFactory.newInstance().createXMLStreamReader(new StringReader(sb.toString()));
>             StAXOMBuilder builder = OMXMLBuilderFactory.createStAXOMBuilder(OMAbstractFactory.getOMFactory(),parser);
>             System.out.println(builder.getDocumentElement().toString());
>             // TRY JDOM (works fine)
>             Document d = new SAXBuilder().build(new StringReader(sb.toString()));
>             new XMLOutputter().output(d, System.out);
>         } catch (Exception e) {
>             e.printStackTrace(System.out);
>         }
>     }
> }

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