Java service which extracts the value of a field at runtime

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1

Hi,

I need to build a java service which extracts the value of a field at runtime. The path of the field in the canonical and the canonical document itself should be given as input.
Eg:
fromDoc consists of sub documents within it, in a hierarchy, ie.
fromDoc/Data/Parameters/outDate

  • fromDoc
    [LIST]
  • Data
    [LIST]
  • Parameters
    [LIST]
  • outDate(string)
    [/LIST]
    [/LIST]
    [/LIST]

For inStringValues I give the input as ‘fromDoc/Data/Parameters/outDate’

the output should return the value of the variable ‘fromDoc/Data/Parameters/outDate’ at run time.

I have a code which implements this with the key value pair logic.

IDataCursor pipelineCursor = pipeline.getCursor();
                // fromDoc
                IData     fromDoc = IDataUtil.getIData( pipelineCursor, "fromDoc" );
                String[] inStringValues = IDataUtil.getStringArray( pipelineCursor, "inStringValues" );
                if ( fromDoc == null)
                {
                    return;
                }
pipelineCursor.destroy();
int len = inStringValues.length;
String[] outStrings = new String[len];
IDataCursor fromCursor = fromDoc.getCursor();
boolean hasData = false;
while( fromCursor.next() )
{
        for(int i=0;i<len;i++)
        {
              String key = fromCursor.getKey();
              String val = fromCursor.getValue().toString();
                  if(key.equals(inStringValues[i]))
                  {
                         outStrings[i]=key + "," + val;
                  }
        }
}
fromCursor.destroy();
IDataCursor pipelineCursor_1 = pipeline.getCursor();
IDataUtil.put( pipelineCursor_1, "outStrings", outStrings );
pipelineCursor_1.destroy();

Please let me know how I can modify this code to implement the above mentioned logic?
Or let me know if anyone has such an existing service with you.

2

Use the XPath API to achieve this. Convert the doc to an XML string and then use an xpath to get the value for a particular field in the xml.

Inputs:
xpathExpression
xmlString

Outputs:
fieldValue
error

Imports:

import org.w3c.dom.*;
import org.xml.sax.SAXException;
import javax.xml.parsers.*;
import javax.xml.xpath.*;

Java Service

        IDataCursor pipelineCursor = pipeline.getCursor();
        String    xpathExpression = IDataUtil.getString( pipelineCursor, "xpathExpression" );
        String    xmlString = IDataUtil.getString( pipelineCursor, "xmlString" );
        pipelineCursor.destroy();
        
        
        DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance();
        domFactory.setNamespaceAware(true);
        
        try {
                InputStream is=new ByteArrayInputStream(xmlString.getBytes("UTF-8"));
                DocumentBuilder builder = domFactory.newDocumentBuilder();
                Document doc = builder.parse(is);
                XPathFactory factory = XPathFactory.newInstance();
                XPath xpath = factory.newXPath();
                XPathExpression expr= xpath.compile(xpathExpression);
        
                //refine this part of the code
                Object result = expr.evaluate(doc, XPathConstants.NODESET);
                NodeList nodes = (NodeList) result;
                 for (int i = 0; i < nodes.getLength(); i++) {
                    IDataUtil.put(pipelineCursor, "fieldValue", nodes.item(i).getNodeValue());
                }
                //end
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
                IDataUtil.put(pipelineCursor, "error", e);
            } catch (SAXException e) {
                e.printStackTrace();
                IDataUtil.put(pipelineCursor, "error", e);
            } catch (IOException e) {
                e.printStackTrace();
                IDataUtil.put(pipelineCursor, "error", e);
            } catch (XPathExpressionException e) {
                e.printStackTrace();
                IDataUtil.put(pipelineCursor, "error", e);
            }
            pipelineCursor.destroy();

Sample input:

/inputDoc/infoDoc/field1/text()

<?xml version="1.0"?>
<inputDoc>
  <infoDoc>
    <field1>abc</field1>
    <field2>123</field2>
  </infoDoc>
</inputDoc>

Output:
abc

3

Alternatives to consider:

  • Just map the value from the IS document.
  • Use pub.xml:queryXMLNode to query the XML node using XQL (assuming the XML node is still available or can be made available)
4

@akki_84: Sounds to me like, as we say in german, “shooting sparrows with cannons”.

I recommend to send in a single string giving the path name, eg something like “doc/subDocLevel2/Level3/Level4/field” and a Document. get the iData for the Pipeline and split the string into components using Java’s String.split(“/”) to get an array of path components. use all but the last to iterate down to the final document and then get the value that it is pointing at.

IDataCursor now = pipeline.getCursor();
String[] components = IDataUtil.getString(now, "path").split("/");
for (int i=0; i < components.length-1) {[INDENT]IDataCursor next = IDataUtil.getIData(now, components[i]).getCursor();
now.destroy();
now = next;[/INDENT]
}
String field = now.GetString(components[components.lenght-1]);
now.destroy();
now = pipeline.getCursor();
IDataUtil.putString(now, "result", field);
now.destroy();

Errorhandling and checking for invalid input (like // in a string or strings starting with / may be added as an exercise.

Thomas

5


If that’s what it takes to get the job done, so be it :slight_smile:

I have a question about your solution though, if there is an array in the IData doc how will the fields under that structure be extracted?

Cheers,
Akshith

6

With extra code. Then you either get an IData or an IData. If you want to deal with arrays too, my recommendation would require extension to understand and handle a syntax like doc/subDoc/subSubDoc[42]/field or whatever is convenient.

something along the lines of

[FONT=courier new]Pattern p = Pattern.compile(".*\\[[0-9]+\\]"); // place outside the loop, need to construct pattern to look for only once[/font]

[FONT=courier new]Matcher m = p.matcher(components[i]); // put into the loop
if (m.find()) {[/font][INDENT][FONT=courier new]// handle array case. error handling left as exercise :)
next = IDataUtils.getIDataArray(now, m.group(0))[Integer.parseInt(m.group(1))].getCursor();[/font][/INDENT]
[FONT=courier new]} else {
  [/font][INDENT][FONT=courier new]// as before[/font][/INDENT]
[FONT=courier new]}
[/font]

shouldnt be too much work to get this one right for a java person.

Thomas

7

Yup, that should do it. Good thread, we learn something new everyday!

I wonder which of the solutions would fare better under a load test though.

Cheers,
Akshith

8

MINE! :slight_smile:

Parsing XML is overkill for the task. Keep things simple. But not too simple.

Thomas