Suppressing unnecessary namespace declarations

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Suppressing unnecessary namespace declarations

by Jeff Carty :: Rate this Message:

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My Atom project makes heavy use of ROME modules. As I mentioned in January, it is annoying (and to some people, even disturbing) to have 30+ xmlns: declarations in every Atom feed we generate, when only 4-5 modules (5-6 namespaces) are needed or used in any one feed.

I asked in January how to get ROME to suppress the excessive declarations, and was told there isn't a way. But there is a way, if you are willing to modify and re-build the ROME source. I offer the following code for anyone with a similar problem... although I really think the ROME developers should fix it in their base code.

Anyway, in com/sun/syndication/io/impl/Atom10Generator.java, I now have this:

public Document generate(WireFeed wFeed) throws FeedException {
Feed feed = (Feed) wFeed;
Element root = createRootElement(feed);
populateFeed(feed,root);
purgeUnusedNamespaceDeclarations(root); // sfly WEB-17627 introduces this line
return createDocument(root);
}

/**
* sfly WEB-17627 introduces this method
*
* Purging unused declarations is less optimal, performance-wise, than never
* adding them in the first place. So, we should still ask the ROME guys to
* fix their code (not adding dozens of unnecessary module declarations).
* Having said that: purging them here, before XML generation, is more
* efficient than parsing and re-molding the XML after ROME generates it.
*
* Note that the calling app could still add declarations/modules to the Feed
* tree after this. Which is fine. But those modules are then responsible
* for crawling to the root of the tree, at generate() time, to make sure
* their namespace declarations are present.
*/
static private void purgeUnusedNamespaceDeclarations(Element root)
{
java.util.Set<String> usedPrefixes = new java.util.HashSet<String>();
collectUsedPrefixes(root, usedPrefixes);

List list = root.getAdditionalNamespaces();
List<org.jdom.Namespace> additionalNamespaces = new java.util.ArrayList<org.jdom.Namespace>();
additionalNamespaces.addAll(list); // the duplication will prevent a ConcurrentModificationException below

for (org.jdom.Namespace ns: additionalNamespaces) {
String prefix = ns.getPrefix();
if (prefix != null && prefix.length() > 0 && !usedPrefixes.contains(prefix)) {
root.removeNamespaceDeclaration(ns);
}
}
return;
}

/**
* sfly WEB-17627 introduces this method
*/
static private void collectUsedPrefixes (Element el, java.util.Set<String> collector)
{
String prefix = el.getNamespacePrefix();
if (prefix != null && prefix.length() > 0 && !collector.contains(prefix)) {
collector.add(prefix);
}
List<org.jdom.Element> kids = el.getChildren();
for (Element kid: kids) {
collectUsedPrefixes (kid, collector); // recursion - worth it
}
}

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Re: Suppressing unnecessary namespace declarations

by Alejandro Abdelnur-2 :: Rate this Message:

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Jeff,

I've just had time to look at it, clever. I'm incorporating it to ROME
code for all generators.

Thanks.

Alejandro

On Sat, Jun 28, 2008 at 12:24 AM, Jeff Carty <jcarty@...> wrote:

> My Atom project makes heavy use of ROME modules. As I mentioned in January, it is annoying (and to some people, even disturbing) to have 30+ xmlns: declarations in every Atom feed we generate, when only 4-5 modules (5-6 namespaces) are needed or used in any one feed.
>
> I asked in January how to get ROME to suppress the excessive declarations, and was told there isn't a way. But there is a way, if you are willing to modify and re-build the ROME source. I offer the following code for anyone with a similar problem... although I really think the ROME developers should fix it in their base code.
>
> Anyway, in com/sun/syndication/io/impl/Atom10Generator.java, I now have this:
>
> public Document generate(WireFeed wFeed) throws FeedException {
> Feed feed = (Feed) wFeed;
> Element root = createRootElement(feed);
> populateFeed(feed,root);
> purgeUnusedNamespaceDeclarations(root); // sfly WEB-17627 introduces this line
> return createDocument(root);
> }
>
> /**
> * sfly WEB-17627 introduces this method
> *
> * Purging unused declarations is less optimal, performance-wise, than never
> * adding them in the first place. So, we should still ask the ROME guys to
> * fix their code (not adding dozens of unnecessary module declarations).
> * Having said that: purging them here, before XML generation, is more
> * efficient than parsing and re-molding the XML after ROME generates it.
> *
> * Note that the calling app could still add declarations/modules to the Feed
> * tree after this. Which is fine. But those modules are then responsible
> * for crawling to the root of the tree, at generate() time, to make sure
> * their namespace declarations are present.
> */
> static private void purgeUnusedNamespaceDeclarations(Element root)
> {
> java.util.Set<String> usedPrefixes = new java.util.HashSet<String>();
> collectUsedPrefixes(root, usedPrefixes);
>
> List list = root.getAdditionalNamespaces();
> List<org.jdom.Namespace> additionalNamespaces = new java.util.ArrayList<org.jdom.Namespace>();
> additionalNamespaces.addAll(list); // the duplication will prevent a ConcurrentModificationException below
>
> for (org.jdom.Namespace ns: additionalNamespaces) {
> String prefix = ns.getPrefix();
> if (prefix != null && prefix.length() > 0 && !usedPrefixes.contains(prefix)) {
> root.removeNamespaceDeclaration(ns);
> }
> }
> return;
> }
>
> /**
> * sfly WEB-17627 introduces this method
> */
> static private void collectUsedPrefixes (Element el, java.util.Set<String> collector)
> {
> String prefix = el.getNamespacePrefix();
> if (prefix != null && prefix.length() > 0 && !collector.contains(prefix)) {
> collector.add(prefix);
> }
> List<org.jdom.Element> kids = el.getChildren();
> for (Element kid: kids) {
> collectUsedPrefixes (kid, collector); // recursion - worth it
> }
> }
>
>
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> To unsubscribe, e-mail: users-unsubscribe@...
> For additional commands, e-mail: users-help@...
>
>

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