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<h2>Processing existing XML</h2>

Groovy provides special XML processing support through the following classes:
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Technology </th>
<th class="confluenceTh"> When/Why to use </th>
<th class="confluenceTh"> Requirements </th>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+using+Groovy%27s+XmlParser" data-linked-resource-id="63526" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML using Groovy's XmlParser" data-base-url="http://docs.codehaus.org">XmlParser</a> </td>
<td class="confluenceTd"> supports GPath expressions for XML documents and allows updating </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+using+Groovy%27s+XmlSlurper" data-linked-resource-id="63524" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML using Groovy's XmlSlurper" data-base-url="http://docs.codehaus.org">XmlSlurper</a> </td>
<td class="confluenceTd"> lower overheads than XmlParser due to lazy evaluation and <a class="confluence-link" href="/display/GROOVY/Updating+XML+with+XmlSlurper" data-linked-resource-id="24248428" data-linked-resource-type="page" data-linked-resource-default-alias="Updating XML with XmlSlurper" data-base-url="http://docs.codehaus.org">allows updating</a> </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+using+Groovy%27s+DOMCategory" data-linked-resource-id="63521" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML using Groovy's DOMCategory" data-base-url="http://docs.codehaus.org">DOMCategory</a> </td>
<td class="confluenceTd"> low-level tree-based processing where you want some syntactic sugar </td>
<td class="confluenceTd"> place <code>use(DOMCategory)</code> around your code </td>
</tr>
</tbody></table>

If you have special needs, you can use one of the many available Java APIs for XML processing. You should consult the documentation of individual APIs for the details, but some examples to get you started are included here:
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Technology </th>
<th class="confluenceTh"> When/Why to use </th>
<th class="confluenceTh"> Requirements </th>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+DOM" data-linked-resource-id="63515" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and DOM" data-base-url="http://docs.codehaus.org">DOM</a> </td>
<td class="confluenceTd"> low-level tree-based processing </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+SAX" data-linked-resource-id="63528" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and SAX" data-base-url="http://docs.codehaus.org">SAX</a> </td>
<td class="confluenceTd"> event-based push-style parsing can be useful for streaming large files </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+StAX" data-linked-resource-id="63531" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and StAX" data-base-url="http://docs.codehaus.org">StAX</a> </td>
<td class="confluenceTd"> event-based pull-style parsing can be useful for streaming large files </td>
<td class="confluenceTd"> requires stax.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+DOM4J" data-linked-resource-id="63628" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and DOM4J" data-base-url="http://docs.codehaus.org">DOM4J</a> </td>
<td class="confluenceTd"> nicer syntax over DOM processing plus can be useful for large files if you use prune capability </td>
<td class="confluenceTd"> requires dom4j.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+XOM" data-linked-resource-id="63619" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and XOM" data-base-url="http://docs.codehaus.org">XOM</a> </td>
<td class="confluenceTd"> nicer syntax over DOM processing plus a strong emphasis on compliancy </td>
<td class="confluenceTd"> requires xom.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+JDOM" data-linked-resource-id="63601" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and JDOM" data-base-url="http://docs.codehaus.org">JDOM</a> </td>
<td class="confluenceTd"> nicer syntax over DOM processing </td>
<td class="confluenceTd"> requires jdom.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Reading+XML+with+Groovy+and+XPath" data-linked-resource-id="63634" data-linked-resource-type="page" data-linked-resource-default-alias="Reading XML with Groovy and XPath" data-base-url="http://docs.codehaus.org">XPath</a> </td>
<td class="confluenceTd"> use XPath expressions </td>
<td class="confluenceTd"> requires Java 5+ or JAXP 1.3+ 
or xalan.jar or jaxen.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Processing+XML+with+XSLT" data-linked-resource-id="77939" data-linked-resource-type="page" data-linked-resource-default-alias="Processing XML with XSLT" data-base-url="http://docs.codehaus.org">XSLT</a> </td>
<td class="confluenceTd"> when your transformation is more easily expressed using XSLT than code </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Processing+XML+with+XQuery" data-linked-resource-id="77928" data-linked-resource-type="page" data-linked-resource-default-alias="Processing XML with XQuery" data-base-url="http://docs.codehaus.org">XQuery</a> </td>
<td class="confluenceTd"> when your transformation is more easily expressed using XQuery than other alternatives </td>
<td class="confluenceTd"> mxquery.jar or alternative </td>
</tr>
</tbody></table>

<h2>Creating new XML</h2>

The most commonly used approach for creating XML with Groovy is to use a builder, i.e. one of:
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Technology </th>
<th class="confluenceTh"> When/Why to use </th>
<th class="confluenceTh"> Requirements </th>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Creating+XML+using+Groovy%27s+MarkupBuilder" data-linked-resource-id="63650" data-linked-resource-type="page" data-linked-resource-default-alias="Creating XML using Groovy's MarkupBuilder" data-base-url="http://docs.codehaus.org">MarkupBuilder</a> </td>
<td class="confluenceTd"> supports Groovy's builder pattern with XML/HTML </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Creating+XML+using+Groovy%27s+StreamingMarkupBuilder" data-linked-resource-id="63662" data-linked-resource-type="page" data-linked-resource-default-alias="Creating XML using Groovy's StreamingMarkupBuilder" data-base-url="http://docs.codehaus.org">StreamingMarkupBuilder</a> </td>
<td class="confluenceTd"> for larger files </td>
<td class="confluenceTd"> - </td>
</tr>
</tbody></table>

Groovy also has some low-level helper classes you typically won't need to use directly but you may sometimes see in older examples of using XML with Groovy.
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Technology </th>
<th class="confluenceTh"> When/Why to use </th>
<th class="confluenceTh"> Requirements </th>
</tr>
<tr>
<td class="confluenceTd"> SAXBuilder </td>
<td class="confluenceTd"> support class when using SAX </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> StreamingSAXBuilder </td>
<td class="confluenceTd"> streaming version of SAXBuilder </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> DOMBuilder </td>
<td class="confluenceTd"> support class when using DOM </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> StreamingDOMBuilder </td>
<td class="confluenceTd"> streaming version of DOMBuilder </td>
<td class="confluenceTd"> - </td>
</tr>
</tbody></table>

You can also use Java API's which support XML document creation:
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Technology </th>
<th class="confluenceTh"> When/Why to use </th>
<th class="confluenceTh"> Requirements </th>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Creating+XML+with+Groovy+and+DOM" data-linked-resource-id="63803" data-linked-resource-type="page" data-linked-resource-default-alias="Creating XML with Groovy and DOM" data-base-url="http://docs.codehaus.org">DOM</a> </td>
<td class="confluenceTd"> low-level creation mechanism </td>
<td class="confluenceTd"> - </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Creating+XML+with+Groovy+and+JDOM" data-linked-resource-id="63807" data-linked-resource-type="page" data-linked-resource-default-alias="Creating XML with Groovy and JDOM" data-base-url="http://docs.codehaus.org">JDOM</a> </td>
<td class="confluenceTd"> if you are an existing JDOM user </td>
<td class="confluenceTd"> requires jdom.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Creating+XML+with+Groovy+and+DOM4J" data-linked-resource-id="63812" data-linked-resource-type="page" data-linked-resource-default-alias="Creating XML with Groovy and DOM4J" data-base-url="http://docs.codehaus.org">DOM4J</a> </td>
<td class="confluenceTd"> if you are an existing DOM4J user </td>
<td class="confluenceTd"> requires dom4j.jar </td>
</tr>
<tr>
<td class="confluenceTd"> <a class="confluence-link" href="/display/GROOVY/Creating+XML+with+Groovy+and+XOM" data-linked-resource-id="63815" data-linked-resource-type="page" data-linked-resource-default-alias="Creating XML with Groovy and XOM" data-base-url="http://docs.codehaus.org">XOM</a> </td>
<td class="confluenceTd"> if you are an existing XOM user </td>
<td class="confluenceTd"> requires xom.jar </td>
</tr>
</tbody></table>

<h2>Updating XML</h2>

<ul>
	<li><a class="confluence-link" href="/display/GROOVY/Updating+XML+with+XmlParser" data-linked-resource-id="24248391" data-linked-resource-type="page" data-linked-resource-default-alias="Updating XML with XmlParser" data-base-url="http://docs.codehaus.org">Updating XML with XmlParser</a></li>
	<li><a class="confluence-link" href="/display/GROOVY/Updating+XML+with+XmlSlurper" data-linked-resource-id="24248428" data-linked-resource-type="page" data-linked-resource-default-alias="Updating XML with XmlSlurper" data-base-url="http://docs.codehaus.org">Updating XML with XmlSlurper</a></li>
	<li><a class="confluence-link" href="/display/GROOVY/Updating+XML+with+DOMCategory" data-linked-resource-id="24248422" data-linked-resource-type="page" data-linked-resource-default-alias="Updating XML with DOMCategory" data-base-url="http://docs.codehaus.org">Updating XML with DOMCategory</a></li>
</ul>

<h2>Validating XML</h2>

<ul>
	<li><a class="confluence-link" href="/display/GROOVY/Validating+XML+with+a+DTD" data-linked-resource-id="79108" data-linked-resource-type="page" data-linked-resource-default-alias="Validating XML with a DTD" data-base-url="http://docs.codehaus.org">Validating XML with a DTD</a></li>
	<li><a class="confluence-link" href="/display/GROOVY/Validating+XML+with+a+W3C+XML+Schema" data-linked-resource-id="79106" data-linked-resource-type="page" data-linked-resource-default-alias="Validating XML with a W3C XML Schema" data-base-url="http://docs.codehaus.org">Validating XML with a W3C XML Schema</a></li>
	<li><a class="confluence-link" href="/display/GROOVY/Validating+XML+with+RELAX+NG" data-linked-resource-id="79111" data-linked-resource-type="page" data-linked-resource-default-alias="Validating XML with RELAX NG" data-base-url="http://docs.codehaus.org">Validating XML with RELAX NG</a></li>
</ul>

<h2>Troubleshooting</h2>

Some of the following Jira issues may indicate solutions or workarounds to problems other users faced while using XML.
<table class="confluenceTable"><tbody>
<tr>
<th class="confluenceTh"> Issue </th>
<th class="confluenceTh"> Description </th>
</tr>
<tr>
<td class="confluenceTd"> <a href="http://jira.codehaus.org/browse/GROOVY-2126">GROOVY-2126</a> </td>
<td class="confluenceTd"> ClassCastException when using java.util.prefs package </td>
</tr>
</tbody></table>

<h2>More Information</h2>

For some more discussion of the pro's and con's of your XML Processing options and some additional details, see the following books:
<ul>
	<li>Chapter 12 of <a href="http://groovy.canoo.com/gina">GINA</a></li>
	<li><a href="http://www.cafeconleche.org/books/xmljava/">Processing XML with Java</a></li>
	<li><a href="http://www.apress.com/book/bookDisplay.html?bID=10157">Pro XML Development with Java Technology</a></li>
	<li><a href="http://www.oreilly.com/catalog/javaxml/">Java and XML</a></li>
</ul>

The following articles may also be of interest:
<ul>
	<li><a href="http://today.java.net/pub/a/today/2004/08/12/groovyxml.html">Getting Groovy with XML</a> by Jack Herrington.</li>
	<li><a href="http://www-128.ibm.com/developerworks/xml/library/x-injava/index.html">XML and Java technologies: Document models, Part 1: Performance</a></li>
	<li><a href="http://www.dom4j.org/compare.html">DOM, DOM4J, JDOM, XOM Comparison</a> (slightly outdated)</li>
	<li><a href="http://www.dom4j.org/benchmarks/xpath/index.html">Dom4J performance versus Xerces / Xalan</a></li>
	<li><a href="http://evc-cit.info/dom4j/dom4j_groovy.html">Hints for parsing XHTML with DOM4J</a></li>
</ul>

You may also be interested in how XML is applied in other parts of Groovy:
<ul>
	<li><a class="confluence-link" href="/display/GROOVY/GroovyWS" data-linked-resource-id="9242181" data-linked-resource-type="page" data-linked-resource-default-alias="GroovyWS" data-base-url="http://docs.codehaus.org">GroovyWS</a> for creating Web Services and Clients (or for JDK 1.4 with Groovy 1.5 also see <a class="confluence-link" href="/display/GROOVY/Groovy+SOAP" data-linked-resource-id="49064" data-linked-resource-type="page" data-linked-resource-default-alias="Groovy SOAP" data-base-url="http://docs.codehaus.org">Groovy SOAP</a>)</li>
	<li><a class="confluence-link" href="/display/GROOVY/Testing+Web+Services" data-linked-resource-id="59173" data-linked-resource-type="page" data-linked-resource-default-alias="Testing Web Services" data-base-url="http://docs.codehaus.org">Testing Web Services</a></li>
	<li><a class="confluence-link" href="/display/GROOVY/Testing+Web+Applications" data-linked-resource-id="59176" data-linked-resource-type="page" data-linked-resource-default-alias="Testing Web Applications" data-base-url="http://docs.codehaus.org">Testing Web Applications</a></li>
</ul>