DO NOT REPLY [Bug 13131] New: - [PATCH] XMLModule: Allow XPath access to arbitrary XML sources

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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=13131

[PATCH] XMLModule: Allow XPath access to arbitrary XML sources

           Summary: [PATCH] XMLModule: Allow XPath access to arbitrary XML
                    sources
           Product: Cocoon 2
           Version: Current CVS
          Platform: Other
        OS/Version: Other
            Status: NEW
          Severity: Enhancement
          Priority: Other
         Component: sitemap components
        AssignedTo: cocoon-dev@xml.apache.org
        ReportedBy: jefft@apache.org


Hi,

Attached is an XMLModule input module, that allows XPath access to any XML
document, specified as a Source.

The code is very simple, building on AbstractJXPathModule. It is pretty powerful
though, because it can access XML from *any* Source. So you can access:
 - static XML (context://..)
 - XML generated dynamically by the sitemap (cocoon://)
 - XML retrieved from HTTP (http://..), Xindice, any other source.. you get the
picture.

As a stupid example of what you can do, here's how you could access Slashdot
headlines from a sitemap:

// In cocoon.xconf:

<component-instance class="org.apache.cocoon.components.modules.input.XMLModule"
logger="core.modules.xml" name="slashdot">
    <config>http://slashdot.org/slashdot.rss</config>
  </component-instance>

Then access the first headline with: {slashdot:/*:RDF/item[1]/title}

A less stupid example: accessing a Forrest config file:

// cocoon.xconf
<component-instance class="org.apache.cocoon.components.modules.input.XMLModule"
logger="core.modules.xml" name="myxml">
  <config>context:///samples/modules/forrestconf.xml</config>
</component-instance>

The file is now accessible with variables like:

{myxml:/forrestconf/@version}
{myxml://skin}


The patch includes modifications to samples/modules to demonstrate the XMLModule.

I also modified AbstractJXPathModule slightly, to allow subclasses'
getContextObject() method to throw ConfigurationExceptions.

One issue is caching: XMLModule doesn't do any. It is thus horribly inefficient,
doing a Source resolve and XML parse for every variable lookup. I'm not sure how
to fix this. Is it XMLModule's concern or AbstractJXPath's? Would caching the
JXPathContext help? Would XMLModule just do a lookup of the MRUMemoryStore
Component, and store Source objects in it, and generally manage caching by hand?
Um. 


--Jeff

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