Develop Reference

How to transform each xml node with Saxon XSLT?

How can I use Saxon xslt transformation library to convert an xml file that contains many nodes to a plain csv string? Means, I want Saxon to concatenate each employee entry as csv, and put them all together.
This is the saxon setup, but I don't know how I could not transform an input xml file with it:
//false = does not required a feature from a licensed version of Saxon.
Processor processor = new Processor(false);
XsltCompiler compiler = processor.newXsltCompiler();
compiler.compile(new StreamSource("transformation.xslt"));
Serializer serializer = processor.newSerializer();
serializer.setOutputProperty(Serializer.Property.OMIT_XML_DECLARATION, "yes");
//TODO
//String result = serializer...serializeNodeToString();
I want to transform the following xml:
<employees stage="test">
<employee>
<details>
<name>Joe</name>
<age>34</age>
</details>
<address>
<street>test</street>
<nr>12</nr>
</address>
</employee>
<employee>
<address>....</address>
<details>
<!-- note the changed order of elements! -->
<age>24</age>
<name>Sam</name>
</details>
</employee>
</employees>
The result string should contain the following (one big string with linebreak separated csv lines):
test,Joe,34,test,12\n
test,Sam,24,...\n
Xslt might be similar to:
<xsl:transform version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="employee">
<xsl:value-of select="name"/>
<xsl:value-of select="age"/>
</xsl:template>
</xsl:transform>

The XSLT template can be modified as below. The elements can be selected according to the required sequence.
<xsl:template match="employee">
<xsl:value-of select="ancestor::employees/#stage, details/name, details/age, address/street, address/nr" separator=", " />
<xsl:text>
</xsl:text>
</xsl:template>
After replacing the ... with some dummy values in the <address> element the following output is generated using the above template.
test, Joe, 34, test, 12
test, Sam, 24, test1, 123
For transforming the XML (using XSLT) in Java, I use the following code snippet most of the time. This method returns the transformed XML as a String. The required library is saxon9he.jar. You may have to upgrade the library version for using with XSLT 3.0
public static String transformXML(String xml, InputStream xslFile) {
String outputXML = null;
try {
System.setProperty("javax.xml.transform.TransformerFactory", "net.sf.saxon.TransformerFactoryImpl");
TransformerFactory factory = TransformerFactory.newInstance();
Transformer transformer = factory.newTransformer(new StreamSource(xslFile));
Source xmlStream = new StreamSource(new StringReader(xml));
StringWriter writer = new StringWriter();
Result result = new StreamResult(writer);
transformer.transform(xmlStream, result);
outputXML = writer.getBuffer().toString();
} catch (TransformerConfigurationException tce) {
tce.printStackTrace();
} catch (TransformerException te) {
te.printStackTrace();
}
return outputXML;
}

Xpath - Java - Extracting multiple namespaces from XML

I am working on a parser written in Java. I can receive XML feeds from various locations, with various contents. I need to extract all the namespaces from the feed, to call this or that according to the feed. I have some trouble obtaining this in Java, and i am not really sure where the issue is.
Let's consider this XML:
<?xml version="1.0"?>
<?xml-stylesheet type='text/xsl' href='new.xsl'?>
<test xmlns:mynsone="http://www.ns.com/test" xmlns:demons="http://www.demons.com/test">
<p xmlns:domain="http://www.toto.com/test">
this is a test.
</p>
</test>
In order to test my xPath expression (i am rather new to it), i wrote a little .xsl script applied to that XML:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output
method="html"
encoding="ISO-8859-1"
doctype-public="-//W3C//DTD XHTML//EN"
doctype-system="http://www.w3.org/TR/2001/REC-xhtml11-20010531"
indent="yes" />
<xsl:template match="/">
<xsl:for-each select="//namespace::*">
<xsl:value-of select="." />
<xsl:text> </xsl:text><br />
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
And this correctly provides me the list of namespaces encountered iterating the nodes:
http://www.w3.org/XML/1998/namespace
http://www.demons.com/test
http://www.ns.com/test
http://www.w3.org/XML/1998/namespace
http://www.demons.com/test
http://www.ns.com/test
http://www.toto.com/test
Now i get back to Java: here is the code i use.
InputStream file = url.openStream();
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = builderFactory.newDocumentBuilder();
org.w3c.dom.Document xmlDocument = builder.parse(file);
XPath xPath = XPathFactory.newInstance().newXPath();
String expression = "//namespace::*";
System.out.println(expression);
NodeList nodelist = (NodeList) xPath.compile(expression).evaluate(xmlDocument, XPathConstants.NODESET);
for (int k = 0; k < nodelist.getLength(); k++)
{
Node mynode = nodelist.item(k);
System.out.println(mynode.toString());
}
And here is the result i obtain:
xmlns:mynsone="http://www.ns.com/test"
org.apache.xml.dtm.ref.dom2dtm.DOM2DTMdefaultNamespaceDeclarationNode#7dbb8ca4
xmlns:domain="http://www.toto.com/test"
Therefore, the "demons" namespace is not returned. The problem is that if i put several namespaces on 1 node, only 1 is return in Java, whereas on the XSL script all are displayed.
I hope i maed myself clear; i spent the past days on the web browsing for examples, and i dont know if im really close but just missing a little something or if my expression is simply not proper..
Thanks in advance.
OK so i eventually used xPath 2.0 to do it, using saxon-HE 9.4:
public static boolean detectGeoRssNamespace(InputStream sourceFeed) {
try {
if (sourceFeed.markSupported()) {
sourceFeed.reset();
}
String objectModel = NamespaceConstant.OBJECT_MODEL_SAXON;
System.setProperty("javax.xml.xpath.XPathFactory:"+NamespaceConstant.OBJECT_MODEL_SAXON, "net.sf.saxon.xpath.XPathFactoryImpl");
XPathFactory xpathFactory = XPathFactory.newInstance(objectModel);
XPath xpath = xpathFactory.newXPath();
InputSource is = new InputSource(sourceFeed);
SAXSource ss = new SAXSource(is);
NodeInfo doc = ((XPathEvaluator)xpath).setSource(ss);
String xpathExpressionStr = "distinct-values(//*[name()!=local-name()]/ concat('prefix=', substring-before(name(), ':'), '&uri=', namespace-uri()))";
XPathExpression xpathExpression = xpath.compile(xpathExpressionStr);
List nodelist = (List)xpathExpression.evaluate(doc, XPathConstants.NODESET);
System.out.println("<output>");
Iterator iter = nodelist.iterator();
while ( iter.hasNext() ) {
Object line = (Object)iter.next();
System.out.println(line.toString());
}
System.out.println("</output>");
} catch (XPathFactoryConfigurationException e) {
e.printStackTrace();
} catch (XPathException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}

what if you extract this namespaces to different xml elements.
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output
method="html"
encoding="ISO-8859-1"
doctype-public="-//W3C//DTD XHTML//EN"
doctype-system="http://www.w3.org/TR/2001/REC-xhtml11-20010531"
indent="yes" />
<xsl:template match="/">
<xsl:for-each select="//namespace::*">
<namespace>
<xsl:value-of select="." />
</namespace>
<xsl:text> </xsl:text><br />
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>

Question was solved using xPath 2.0 (code included in question)

Boolean operation in Xpath: Using attributes

Following is a snippet of .xml file. I did following :
Document doc = docBuilder.parse(filesInDirectory.get(i));
doc.getDocumentElement().normalize();
XPath xPath = XPathFactory.newInstance().newXPath();
XPathExpression expr1 = xPath.compile("//codes[# class ='class2']/code[#code]");
Object result1 = expr1.evaluate(doc, XPathConstants.NODESET);
NodeList nodes1 = (NodeList) result1;
Now,
System.out.println("result length"+":"+nodes1.getLength());
returns 2.
I would like to make logical decision based on the attribute names, like(pseudocode)
if(nodes1.contains(123))
or
if(nodes1.contains(123) && nodes1.contains(456))
and make decision.
how would i do it?
<metadata>
<codes class="class1">
<code code="ABC">
<detail "blah" "blah">
</code>
</codes>
<codes class="class2">
<code code="123">
<detail "blah blah"/>
</code>
<code code="456">
<detail "blah blah"/>
</code>
</codes>
</metadata>

This:
XPathExpression expr1 = xPath.compile("//codes[#class]");
Object result1 = expr1.evaluate(doc, XPathConstants.NODESET);
NodeList nodes1 = (NodeList) result1;
should return you a list of elements with a class attribute. Iterate over this node list and foreach node extract the [#code] element and use a check like
if (node.getNodeValue().equals("123"))
to establish whether your node has the value you are looking for.

Try out this:
File f = new File("test.xml");
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
InputSource src = new InputSource(new FileInputStream(f));
Object result = xpath.evaluate("//codes[#class='class2']/code/#code",src,XPathConstants.NODESET);
NodeList lst = (NodeList)result;
List<String> codeList = new ArrayList<String>();
for(int idx=0; idx<lst.getLength(); idx++){
codeList.add(lst.item(idx).getNodeValue());
}
if(codeList.contains("123")){
System.out.println("123");
}
if(codeList.contains("123") && codeList.contains("456")){
System.out.println("123 and 456");
}
Explanation:
XPath //codes[#class='class2']/code/#code will collect all code values under codes with having class as class2.
You can then build a List from NodeList so that you can use contains() method.

Use this XPath expression:
/*/codes[#class]/code[#code = '123' or #code = '456']
It selects any code element whose code attribute's string value is one of the strings "123" or "456" and that (the code element) is a child of a codes element that has a `class attribute and is a child of the top element of the XML document.
XSLT - based verification:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="/">
<xsl:copy-of select=
"/*/codes[#class]/code[#code = '123' or #code = '456']"/>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the provided XML document (corrected to be made well-formed):
<metadata>
<codes class="class1">
<code code="ABC">
<detail/>
</code>
</codes>
<codes class="class2">
<code code="123">
<detail />
</code>
<code code="456">
<detail />
</code>
</codes>
</metadata>
the XPath expression is evaluated and the selected nodes are copied to the output:
<code code="123">
<detail/>
</code>
<code code="456">
<detail/>
</code>
Explanation:
Proper use of the standard XPath operator or.

How to Generate an XML File from a set of XPath Expressions?

I want to be able to generate a complete XML file, given a set of XPath mappings.
The input could specified in two mappings: (1) One which lists the XPath expressions and values; and (2) the other which defines the appropriate namespaces.
/create/article[1]/id => 1
/create/article[1]/description => bar
/create/article[1]/name[1] => foo
/create/article[1]/price[1]/amount => 00.00
/create/article[1]/price[1]/currency => USD
/create/article[2]/id => 2
/create/article[2]/description => some name
/create/article[2]/name[1] => some description
/create/article[2]/price[1]/amount => 00.01
/create/article[2]/price[1]/currency => USD
For namespaces:
/create => xmlns:ns1='http://predic8.com/wsdl/material/ArticleService/1/
/create/article => xmlns:ns1='http://predic8.com/material/1/‘
/create/article/price => xmlns:ns1='http://predic8.com/common/1/‘
/create/article/id => xmlns:ns1='http://predic8.com/material/1/'
Note also, that it is important that I also deal with XPath Attributes expressions as well. For example: I should also be able to handle attributes, such as:
/create/article/#type => richtext
The final output should then look something like:
<ns1:create xmlns:ns1='http://predic8.com/wsdl/material/ArticleService/1/'>
<ns1:article xmlns:ns1='http://predic8.com/material/1/‘ type='richtext'>
<name>foo</name>
<description>bar</description>
<ns1:price xmlns:ns1='http://predic8.com/common/1/'>
<amount>00.00</amount>
<currency>USD</currency>
</ns1:price>
<ns1:id xmlns:ns1='http://predic8.com/material/1/'>1</ns1:id>
</ns1:article>
<ns1:article xmlns:ns1='http://predic8.com/material/2/‘ type='richtext'>
<name>some name</name>
<description>some description</description>
<ns1:price xmlns:ns1='http://predic8.com/common/2/'>
<amount>00.01</amount>
<currency>USD</currency>
</ns1:price>
<ns1:id xmlns:ns1='http://predic8.com/material/2/'>2</ns1:id>
</ns1:article>
</ns1:create>
PS: This is a more detailed question to a previous question asked, although due to a series of further requirements and clarifications, I was recommended to ask a more broader question in order to address my needs.
Note also, I am implementing this in Java. So either a Java-based or XSLT-based solution would both be perfectly acceptable. thnx.
Further note: I am really looking for a generic solution. The XML shown above is just an example.

This problem has an easy solution if one builds upon the solution of the previous problem:
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:key name="kNSFor" match="namespace" use="#of"/>
<xsl:variable name="vStylesheet" select="document('')"/>
<xsl:variable name="vPop" as="element()*">
<item path="/create/article/#type">richtext</item>
<item path="/create/article/#lang">en-us</item>
<item path="/create/article[1]/id">1</item>
<item path="/create/article[1]/description">bar</item>
<item path="/create/article[1]/name[1]">foo</item>
<item path="/create/article[1]/price[1]/amount">00.00</item>
<item path="/create/article[1]/price[1]/currency">USD</item>
<item path="/create/article[1]/price[2]/amount">11.11</item>
<item path="/create/article[1]/price[2]/currency">AUD</item>
<item path="/create/article[2]/id">2</item>
<item path="/create/article[2]/description">some name</item>
<item path="/create/article[2]/name[1]">some description</item>
<item path="/create/article[2]/price[1]/amount">00.01</item>
<item path="/create/article[2]/price[1]/currency">USD</item>
<namespace of="create" prefix="ns1:"
url="http://predic8.com/wsdl/material/ArticleService/1/"/>
<namespace of="article" prefix="ns1:"
url="xmlns:ns1='http://predic8.com/material/1/"/>
<namespace of="#lang" prefix="xml:"
url="http://www.w3.org/XML/1998/namespace"/>
<namespace of="price" prefix="ns1:"
url="xmlns:ns1='http://predic8.com/material/1/"/>
<namespace of="id" prefix="ns1:"
url="xmlns:ns1='http://predic8.com/material/1/"/>
</xsl:variable>
<xsl:template match="/">
<xsl:sequence select="my:subTree($vPop/#path/concat(.,'/',string(..)))"/>
</xsl:template>
<xsl:function name="my:subTree" as="node()*">
<xsl:param name="pPaths" as="xs:string*"/>
<xsl:for-each-group select="$pPaths" group-adjacent=
"substring-before(substring-after(concat(., '/'), '/'), '/')">
<xsl:if test="current-grouping-key()">
<xsl:choose>
<xsl:when test=
"substring-after(current-group()[1], current-grouping-key())">
<xsl:variable name="vLocal-name" select=
"substring-before(concat(current-grouping-key(), '['), '[')"/>
<xsl:variable name="vNamespace"
select="key('kNSFor', $vLocal-name, $vStylesheet)"/>
<xsl:choose>
<xsl:when test="starts-with($vLocal-name, '#')">
<xsl:attribute name=
"{$vNamespace/#prefix}{substring($vLocal-name,2)}"
namespace="{$vNamespace/#url}">
<xsl:value-of select=
"substring(
substring-after(current-group(), current-grouping-key()),
2
)"/>
</xsl:attribute>
</xsl:when>
<xsl:otherwise>
<xsl:element name="{$vNamespace/#prefix}{$vLocal-name}"
namespace="{$vNamespace/#url}">
<xsl:sequence select=
"my:subTree(for $s in current-group()
return
concat('/',substring-after(substring($s, 2),'/'))
)
"/>
</xsl:element>
</xsl:otherwise>
</xsl:choose>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="current-grouping-key()"/>
</xsl:otherwise>
</xsl:choose>
</xsl:if>
</xsl:for-each-group>
</xsl:function>
</xsl:stylesheet>
When this transformation is applied on any XML document (not used), the wanted, correct result is produced:
<ns1:create xmlns:ns1="http://predic8.com/wsdl/material/ArticleService/1/">
<ns1:article xmlns:ns1="xmlns:ns1='http://predic8.com/material/1/" type="richtext"
xml:lang="en-us"/>
<ns1:article xmlns:ns1="xmlns:ns1='http://predic8.com/material/1/">
<ns1:id>1</ns1:id>
<description>bar</description>
<name>foo</name>
<ns1:price>
<amount>00.00</amount>
<currency>USD</currency>
</ns1:price>
<ns1:price>
<amount>11.11</amount>
<currency>AUD</currency>
</ns1:price>
</ns1:article>
<ns1:article xmlns:ns1="xmlns:ns1='http://predic8.com/material/1/">
<ns1:id>2</ns1:id>
<description>some name</description>
<name>some description</name>
<ns1:price>
<amount>00.01</amount>
<currency>USD</currency>
</ns1:price>
</ns1:article>
</ns1:create>
Explanation:
A reasonable assumption is made that throughout the generated document any two elements with the same local-name() belong to the same namespace -- this covers the predominant majority of real-world XML documents.
The namespace specifications follow the path specifications. A nsmespace specification has the form: <namespace of="target element's local-name" prefix="wanted prefix" url="namespace-uri"/>
Before generating an element with xsl:element, the appropriate namespace specification is selected using an index created by an xsl:key. From this namespace specification the values of its prefix and url attributes are used in specifying in the xsl:element instruction the values of the full element name and the element's namespace-uri.

Interesting question. Let's assume that your input set of XPath expressions satisfies some reasonsable constraints, for example if there is an X/article[2] then there also (preceding it) an X/article[1]. And let's put the namespace part of the problem to one side for the moment.
Let's go for an XSLT 2.0 solution: we'll start with the input in the form
<paths>
<path value="1">/create/article[1]/id</path>
<path value="bar">/create/article[1]/description</path>
</paths>
and then we'll turn this into
<paths>
<path value="1"><step>create</step><step>article[1]</step><step>id</step></path>
...
</paths>
Now we'll call a function which does a grouping on the first step, and calls itself recursively to do grouping on the next step:
<xsl:function name="f:group">
<xsl:param name="paths" as="element(path)*"/>
<xsl:param name="step" as="xs:integer"/>
<xsl:for-each-group select="$paths" group-by="step[$step]">
<xsl:element name="{replace(current-grouping-key(), '\[.*', '')}">
<xsl:choose>
<xsl:when test="count(current-group) gt 1">
<xsl:sequence select="f:group(current-group(), $step+1)"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="current-group()[1]/#value"/>
</xsl:otherwise>
</xsl:choose>
</xsl:element>
</xsl:for-each-group>
</xsl:function>
That's untested, and there may well be details you have to adjust to get it working. But I think the basic approach should work.
The namespace part of the problem is perhaps best tackled by preprocessing the list of paths to add a namespace attribute to each step element; this can then be used in the xsl:element instruction to put the element in the right namespace.

i came across a similar situation where i had to convert Set of XPath/FQN - value mappings to XML. A generic simple solution can be using the following code, which can be enhanced to specific requirements.
public class XMLUtils {
static public String transformToXML(Map<String, String> pathValueMap, String delimiter)
throws ParserConfigurationException, TransformerException {
DocumentBuilderFactory documentFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder documentBuilder = documentFactory.newDocumentBuilder();
Document document = documentBuilder.newDocument();
Element rootElement = null;
Iterator<Entry<String, String>> it = pathValueMap.entrySet().iterator();
while (it.hasNext()) {
Entry<String, String> pair = it.next();
if (pair.getKey() != null && pair.getKey() != "" && rootElement == null) {
String[] pathValuesplit = pair.getKey().split(delimiter);
rootElement = document.createElement(pathValuesplit[0]);
break;
}
}
document.appendChild(rootElement);
Element rootNode = rootElement;
Iterator<Entry<String, String>> iterator = pathValueMap.entrySet().iterator();
while (iterator.hasNext()) {
Entry<String, String> pair = iterator.next();
if (pair.getKey() != null && pair.getKey() != "" && rootElement != null) {
String[] pathValuesplit = pair.getKey().split(delimiter);
if (pathValuesplit[0].equals(rootElement.getNodeName())) {
int i = pathValuesplit.length;
Element parentNode = rootNode;
int j = 1;
while (j < i) {
Element child = null;
NodeList childNodes = parentNode.getChildNodes();
for (int k = 0; k < childNodes.getLength(); k++) {
if (childNodes.item(k).getNodeName().equals(pathValuesplit[j])
&& childNodes.item(k) instanceof Element) {
child = (Element) childNodes.item(k);
break;
}
}
if (child == null) {
child = document.createElement(pathValuesplit[j]);
if (j == (i - 1)) {
child.appendChild(
document.createTextNode(pair.getValue() == null ? "" : pair.getValue()));
}
}
parentNode.appendChild(child);
parentNode = child;
j++;
}
} else {
// ignore any other root - add logger
System.out.println("Data not processed for node: " + pair.getKey());
}
}
}
TransformerFactory transformerFactory = TransformerFactory.newInstance();
Transformer transformer = transformerFactory.newTransformer();
DOMSource domSource = new DOMSource(document);
// to return a XMLstring in response to an API
StringWriter writer = new StringWriter();
StreamResult result = new StreamResult(writer);
StreamResult resultToFile = new StreamResult(new File("C:/EclipseProgramOutputs/GeneratedXMLFromPathValue.xml"));
transformer.transform(domSource, resultToFile);
transformer.transform(domSource, result);
return writer.toString();
}
public static void main(String args[])
{
Map<String, String> pathValueMap = new HashMap<String, String>();
String delimiter = "/";
pathValueMap.put("create/article__1/id", "1");
pathValueMap.put("create/article__1/description", "something");
pathValueMap.put("create/article__1/name", "Book Name");
pathValueMap.put("create/article__1/price/amount", "120" );
pathValueMap.put("create/article__1/price/currency", "INR");
pathValueMap.put("create/article__2/id", "2");
pathValueMap.put("create/article__2/description", "something else");
pathValueMap.put("create/article__2/name", "Book name 1");
pathValueMap.put("create/article__2/price/amount", "2100");
pathValueMap.put("create/article__2/price/currency", "USD");
try {
XMLUtils.transformToXML(pathValueMap, delimiter);
} catch (ParserConfigurationException | TransformerException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}}
Output:
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<create>
<article__1>
<id>1</id>
<name>Book Name</name>
<description>something</description>
<price>
<currency>INR</currency>
<amount>120</amount>
</price>
</article__1>
<article__2>
<description>something else</description>
<name>Book name 1</name>
<id>2</id>
<price>
<currency>USD</currency>
<amount>2100</amount>
</price>
</article__2>
To remove __%num , can use regular expressions on final string. like:
resultString = resultString.replaceAll("(__[0-9][0-9])|(__[0-9])", "");
This would do the cleaning job

Changing node name of xml-node with Java

I have following scenario: I have a XML-Document, e.g. like this
<someRootElement>
<tag1>
<tag2
someKey=someValue
someKey2=someValue2
/>
<tag3/>
<tag4
newKey=newValue
newKey2=newValue2
/>
</tag1>
</someRootElement>
Now I want the parent tag1 to be called reallyCoolTag without losing the childnodes.
I tried the following, but it unfortunately doesn't work as I wish it would (but I do know why, b/c it is missing something, I guess):
// the new element:
Element neu = doc.createElement( newValue );
// append it to the root:
root.appendChild( neu );
// get all the child nodes:
NamedNodeMap nnm = nodes.item(i).getAttributes();
for( int dg = 0; dg < nnm.getLength(); dg++ ){
neu.setAttribute( nnm.item( dg ).getNodeName(),
nnm.item( dg ).getNodeValue() );
}
//---------------------------------------------------------
// HERE I GUESS I AM MISSING THE PART WHERE THE CHILD NODES
// ARE BEING APPENDED TO THE NEW NODE?????
//---------------------------------------------------------
// nodes.item(i) := the old value (nodes := is a NodeList
root.replaceChild( neu, nodes.item(i));
TransformerFactory tFactory = TransformerFactory.newInstance();
Transformer transformer = tFactory.newTransformer();
DOMSource source = new DOMSource( doc );
StreamResult result = new StreamResult( xml );
transformer.transform( source, result );
nodes.item( i ).getParentNode().removeChild( nodes.item(i) );
Now this does work to a certain extend, as I mentioned, I guess I am missing the part where the child nodes are being appened, but what I actually wanted to know is, whether there is a really short way to rename the parent node without having to copy everything and replace the whole thing?
Thnx in advance!!!

Using Document.renameNode:
NodeList nodes = document.getElementsByTagName("tag1");
for (Node eachNode: nodes) {
document.renameNode(eachNode, null, "reallyCoolTag");
}

You could use an XSL Transformation (XSLT) for this:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output method="xml" indent="yes" />
<xsl:template match="*"> <!-- match anything -->
<xsl:copy>
<xsl:copy-of select="#*" />
<xsl:apply-templates />
</xsl:copy>
</xsl:template>
<xsl:template match="tag1"> <!-- switch the element name -->
<xsl:element name="reallyCoolTag">
<xsl:copy-of select="#*" />
<xsl:apply-templates />
</xsl:element>
</xsl:template>
</xsl:stylesheet>
This can be used with the javax.xml.transform package (Java 1.4 and above):
TransformerFactory transFactory = TransformerFactory.newInstance();
Transformer transformer = transFactory.newTransformer(new StreamSource(
new File("RenameTag.xslt")));
transformer
.transform(new DOMSource(document), new StreamResult(System.out));
See DOMResult if you want a Document as the output.

Your tag1 is invalid. It doesn't have closing >. Also the attributes should be quoted. It should look like this,
<someRootElement>
<tag1>
<tag2
someKey="someValue"
someKey2="someValue2"
/>
<tag3/>
<tag4
newKey="newValue"
newKey2="newValue2"
/>
</tag1>
</someRootElement>
Try with the corrected XML. It should work.

Just call setName("reallyCoolTag") on the element(s) you want to rename. There is no need to copy the children around; the name attribute of an element is a mutable field.

As you did get the attributes:
NamedNodeMap nnm = nodes.item(i).getAttributes();
and you added these attributes to the new element,
You should get the children of nodes.item(i) and set them in the new node.
You can use for ex.:
neu.addContent(nodes.item(i).getChildren());