Using DOM and XPath to Navigate Xsd

[YerMom]

I want to use the classes in javax.xml.xpath to navigate XSDs.

I have an XSD with the following structure:

<?xml version="1.0" standalone="yes"?>
<xs:schema version="1.0" targetNamespace="[URL unfurl="true"]http://www.mycompany.com"[/URL] xmlns:tns="[URL unfurl="true"]http://www.mycompany.com"[/URL] xmlns:xs="[URL unfurl="true"]http://www.w3.org/2001/XMLSchema">[/URL]

<xs:complexType name="MyOperation">
    <xs:sequence>
      <xs:element name="input" type="tns:MyOperationInputMessage" form="qualified" minOccurs="0"/>
    </xs:sequence>
</xs:complexType>

<xs:complexType name="MyOperation2">
    <xs:sequence>
      <xs:element name="input" type="tns:MyOperation2InputMessage" form="qualified" minOccurs="0"/>
    </xs:sequence>
</xs:complexType>

</xs:schema>

This xsd sample is incomplete to keep things simple.

Given an operation name such as "MyOperation" (which will be variable) I need to navigate to the "MyOperation" xs:complextype element and get the value of the "type" attribute of the enclosed xs:element element

Here is a start at what I think I need to do:

DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true); 

DocumentBuilder builder = domFactory.newDocumentBuilder();
Document doc = builder.parse(fileName);
XPath xpath = XPathFactory.newInstance().newXPath();

String opName = "MyOperation";
String attrib = "[@name=".concat("'").concat(opName).concat("'").concat("]");
XPathExpression expr = xpath.compile("/xs:schema/xs:complexType".concat(attrib));
Object result = expr.evaluate(doc, XPathConstants.NODESET);
NodeList nodes = (NodeList) result;

It's very clear I'm lost and this is a guess so I need your help.

Can anyone tell me the correct way to get the value of the "type" attribute of the enclosed xs:element?

Thanks very much.

 

[Diancecht]

I'm not familiar with XPath. If the structure is always the same, I'd go

doc.getElementbyId("MyOperation").getFirstChild().getFirstChild().getNodeType()

You can also check the XML Forum.

Cheers,
Dian

 

[tsuji]

[1] If you want to use namespace prefix, you have to implement the NameContext interface that I see no sign of you having one.

[1.1] In that context, the xpath "expression" looks like this and the type attribute is directly returned. You can apply getNodeValue() to it to retrieve the value.
[tt]
String expression="/xs:schema/xs:complexType[@name='" + opName + "/xs:sequence/xs:element[@name='input']/@type";
[/tt]
You see you seem to miss out quite a bit.

[2] Without implementing the NameContext interface, you can make the NamespaceAware XPath to get the result too. Only this time, you have make heavy use of xpath built-in function. The expression look like this.
[tt]
String expression="/*[local-name()='schema' and namespace-uri()='[ignore]

http://www.w3.org/2001/XMLSchema

[/ignore]']" +
"/*[local-name()='complexType' and namespace-uri()='[ignore]

http://www.w3.org/2001/XMLSchema

[/ignore]' and @name='" + opName + "']" +
"/*[local-name()='sequence' and namespace-uri()='[ignore]

http://www.w3.org/2001/XMLSchema

[/ignore]']"+
"/*[local-name()='element' and namespace-uri()='[ignore]

http://www.w3.org/2001/XMLSchema

[/ignore]' and @name='input']" +
"/@type";
[/tt]
[2.1] You can then apply it directly to what you have got already without doing further consideration of implementing NamespaceContext.

 

[tsuji]

Amendment
I missed out a closing bracket in [1.1] that the line should be read like this.
[tt] String expression="/xs:schema/xs:complexType[@name='" + opName + "[red]'][/red]/xs:sequence/xs:element[@name='input']/@type";
[/tt]

 

[YerMom]

Thanks Dianecht and tsuji.

Dianect -- I need to learn XPath, but thanks for your insight and recommendation of the XML forum.

Tsuji -- Thanks for the detail. I think I'll try implementing the NameContext interface. I've done some preliminary reading on how it can be done but I need to study it more, and do additional reading on namespaces.

Hopefully you'll get notifications for additional postings I'll do on this thread.

Thanks.

 

[YerMom]

For the benefit of anyone who might see this thread, I found a great tutorial and NamespaceContext samples at

http://www.ibm.com/developerworks/l...JAva&S_TACT=105AGX59&S_CMP=grlnxw16#icomments

Thanks Dianect and tsuji for your help.