Custom XPATH Function in SOA 11g

This post will explain how to create a custom function and configure in SOA 11g

1. Create a JAVA Class which we need to use it as a custom function.

2. The XSLT processor needs the custom Xpath function to be implemented as Static Java Method with a particular  signature as mentioned below.

public class SOAConstants
{
  public static class SOAConstantsXPathFunction
    implements IXPathFunction
  {
    public Object call(IXPathContext paramIXPathContext, List paramList)
      throws XPathFunctionException
    {
      if ((paramList.size() == 2) && ((paramList.get(0) instanceof String)) && ((paramList.get(1) instanceof String))) {
        try
        {
          String str = getPropertyValue(paramList);
          return str;
        }
        catch (Exception localException)
        {
          System.out.println("The Exception : " + localException);
        }
      }
      throw new XPathFunctionException("Pass Only the Service name  and Constant name to look up");
    }
   
    private static String getPropertyValue(List paramList)
      throws XPathFunctionException
    {
      System.out.println("Inside getPropertyValue");
      String str1 = null;
      try
      {
        Document localDocument = SOAConstantsReader.getInstance().getConstantsAsDoc();
        String str2 = paramList.get(0).toString();
        String str3 = paramList.get(1).toString();
        System.out.println("-- payload :" + str2 + " - " + str3);
        NodeList localNodeList1 = localDocument.getElementsByTagName(str2);
        System.out.println("Got Service NodeList");
        Element localElement = (Element)localNodeList1.item(0);
        System.out.println("Got Service Element" + localNodeList1.item(0).getChildNodes().getLength());
        NodeList localNodeList2 = localElement.getElementsByTagName(paramList.get(1).toString());
        localElement = (Element)localNodeList2.item(0);
        str1 = localElement.getChildNodes().item(0).getNodeValue();
        System.out.println("\nThe value of property: " + str1);
      }
      catch (Exception localException)
      {
        throw new XPathFunctionException("The Exception : " + localException);
      }
      return str1;
    }
  }
}

3. The name of the method can be anything but it must be static and take the given parameters.

4. Implement a  function for XSLT using below format.

public Object call(IXPathContext paramIXPathContext, List paramList)
      throws XPathFunctionException

5. Note the method/Function name must be CALL and non static

6. Compile the code and create a JAR file to implement in Domain folder.

7. Now we need to create a descriptor to describe to SOA Suite and XSLT processor that what custom function we have created.

8. We do this by creating or updating the below file in META-INF directory which will create during the installation of SOA suite.

ext-soa-xpath-functions-config.xml

PATH =  $FMW_HOME/Oracle_SOA1/soa/modules/oracle.soa.ext_11.1.1/classes/META-INF

9. Edit the above file to add the function details

<?xml version = '1.0' encoding = 'UTF-8'?>
<soa-xpath-functions xmlns="http://xmlns.oracle.com/soa/config/xpath"
version="11.1.1" resourceBundle="oracle.tip.tools.ide.common.resource.IDEMessageBundle" xmlns:ora="http://schemas.oracle.com/xpath/extension"
xmlns:vha="http://www.oracle.com/XSL/Transform/java/com.vha.util.action.SOAConstants"
xmlns:vha1="http://www.oracle.com/XSL/Transform/java/com.vha.util.action.SetCompositeInstanceIndex"
xmlns:vhadvm="http://www.oracle.com/XSL/Transform/java/com.vha.util.dvm.CustomDVMLookup"
>
  <function name="vha:getPropertyValue">
    <className>com.vha.util.action.SOAConstants$SOAConstantsXPathFunction</className>
    <return type="string"/>
    <params>
      <param name="parentTagName" type="string"/>
      <param name="childTagName" type="string"/>
    </params>
    <desc resourceKey="GET_PROPERTY VALUE"/>
    <detail>
       <![CDATA[This function will get the value of element from SOAConstants.xml file]]>
    </detail>
  </function>



10. The namespace for the function must be “http://www.oracle.com/XSL/Transform/java/” followed by the full classname of the impementing class.  This is required by the XSLT processor.  The namespace prefix can be anything

11. The function name can be anything but it must have a namespace prefix.


12. Before using the custom function in JDeveloper it needs to be registered.  To do this in JDeveloper we go to the “SOA” section in “Preferences” and add the newly created jar file.  To make JDeveloper see the file we then need to restart JDeveloper.  After doing this we will see the XPath function appears in the “User Defined Extension Functions” in the expression builder.