Problem Overwriting XML Section

[Randy Miller]

Hi guys!

Some time ago,I tried to find a solution for overwriting a special section inside a big XML with another smaller XML.
Now,I tried and tried,but somehow,my code just won´t work.It doesn´t replace the XML section,it only appends the small XML at the end of the big XML.
Here´s my code:

public class ReplaceSection {

	/**
	 * @param args
	 */
	public static void main(String[] args) { 
		Document doc1 = parseXmlFile("replacementXML", false);  
        NodeList list = doc1.getElementsByTagName("variableParameters");  
        Element element = (Element)list.item(0);  
  
        // Create another document  
        Document doc2 = parseXmlFile("entireXML", false);  
  
        // Make a copy of the element subtree suitable for inserting into doc2  
        Node dup = doc2.importNode(element, true);  
  
        // Insert the copy into doc2  
        doc2.getDocumentElement().appendChild(dup);  
          
        try{  
            Transformer transformer = TransformerFactory.newInstance().newTransformer();     
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");     
            StreamResult result = new StreamResult(new FileWriter("C:\\Output.xml"));     
            DOMSource source = new DOMSource(doc2);     
            transformer.transform(source, result);     
            System.out.println("File saved!");     
          
        }catch(Exception e){  
            e.printStackTrace();  
        }  
		 
	}
	
    // Parses an XML file and returns a DOM document.  
    public static Document parseXmlFile(String filename, boolean validating) {  
        try {  
            // Create a builder factory  
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();  
            factory.setValidating(validating);  
  
            // Create the builder and parse the file  
            Document doc = factory.newDocumentBuilder().parse(new File(filename));  
            return doc;  
        } catch (SAXException e) {  
            // A parsing error occurred; the xml input is not valid  
        } catch (ParserConfigurationException e) {  
        } catch (IOException e) {  
        }  
        return null;  
    }   

}

Does anyone see the problem??I mean,the XMLs are both wellformed and I just can´t see why my program just appends the XML section to the big XML instead of replacing the section with the same name as the replacing section xml inside the big XML.

I hope,you can help me!

Greetings,

Randy

[Paul Clapham]

From the API documentation for appendChild():

Adds the node newChild to the end of the list of children of this node.

If you want to replace a node, I suggest you consider a method which has "replace" in its name. Check the API documentation for that one.

[Randy Miller]

Ah,ok,now that explains why the node is appended at the end of the file.
So,I tried to get it to work with the replaceChild() method,but still it won´t work. Just won´t replace it and the program doesn´t really wanna jump into my saving-method(Transformer stuff^^)
Here´s my next try:

public static void replace() { 
				
		try {  
		    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();  
		    DocumentBuilder db = dbf.newDocumentBuilder();  
		    Document doc1;  
		    try {  
		    doc1 = db.parse(new File(replacementXMLPath));   
		    Document doc2;  
		    doc2 = db.parse(new File(entireXMLPath));   
		       
		   Element personElement = doc1.getDocumentElement();    
		   NodeList nl = personElement.getChildNodes();    
		   Node nodeToBeReplaced = null;    
		   for (int i = 0 ; i < nl.getLength(); i++){    
		    Node childNode = nl.item(i);    
		    if (childNode.getNodeName().equals(replacementNodeName)){    
		        nodeToBeReplaced = childNode;   
		        personElement.replaceChild(doc1.importNode(doc2.getDocumentElement(),true),nodeToBeReplaced);  
		        
		        try {
					Transformer transformer = TransformerFactory.newInstance()
							.newTransformer();
					transformer.setOutputProperty(OutputKeys.INDENT, "yes");
					StreamResult result = new StreamResult(new FileWriter(
							"C:\\Output.xml"));
					DOMSource source = new DOMSource(doc2);
					transformer.transform(source, result);
					System.out.println("File saved!");

				} catch (Exception e) {
					e.printStackTrace();
				}
		       // break;    
		    }    
		   }    
		   if (nodeToBeReplaced != null){    
		    personElement.replaceChild(doc1.importNode(doc2.getDocumentElement(),true),nodeToBeReplaced);  
		    //save(doc2);
		    System.out.print(doc1);
		   }  
		     
		    } catch (SAXException e) {  
		        // TODO Auto-generated catch block  
		        e.printStackTrace();  
		    } catch (IOException io) {  
		        // TODO Auto-generated catch block  
		        io.printStackTrace();  
		    }  
		} catch(ParserConfigurationException pce){  
		    pce.printStackTrace();  
		}  
	}

[Paul Clapham]

Well, I have to say that I don't understand your code. Based on what you said earlier and based on some of the variable names, I have a vague feeling that maybe you should be trying to replace one of the nodes of doc2 by the contents of doc1, rather than what you're doing now. But calling the documents "doc1" and "doc2" is quite unhelpful.

[Randy Miller]

Hi Paul!

Sorry for the unclear code ;)
I tried to name the deciding elements a bit differently, so it´s easier to understand.And I also put the saving mechanism into a new function.

public static void replace() {

		try {
			DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
			DocumentBuilder db = dbf.newDocumentBuilder();
			Document replacementDoc;
			Document entireDoc;
			
			replacementDoc = db.parse(new File(replacementXMLPath));
			entireDoc = db.parse(new File(entireXMLPath));

			Element changeElement = replacementDoc.getDocumentElement();
			NodeList nl = changeElement.getChildNodes();
			Node nodeToBeReplaced = null;
			
			for (int i = 0; i < nl.getLength(); i++) {
				Node childNode = nl.item(i);
				
				if (childNode.getNodeName().equals(nodeThatShouldBeReplaced)) {
					nodeToBeReplaced = childNode;
					changeElement.replaceChild(entireDoc.importNode(
							replacementDoc.getDocumentElement(), true),
							nodeToBeReplaced);
					save(entireDoc);
				}
			}
			if (nodeToBeReplaced != null) {
				changeElement.replaceChild(entireDoc.importNode(replacementDoc
						.getDocumentElement(), true), nodeToBeReplaced);
				save(entireDoc);

			}

		} catch (SAXException e) {
			e.printStackTrace();
			
		} catch (IOException io) {
			io.printStackTrace();
			
		} catch (ParserConfigurationException e) {
			e.printStackTrace();
		}

	}

	// Parses an XML file and returns a DOM document.
	public static Document parseXmlFile(String filename, boolean validating) {
		try {
			// Create a builder factory
			DocumentBuilderFactory factory = DocumentBuilderFactory
					.newInstance();
			factory.setValidating(validating);

			// Create the builder and parse the file
			Document doc = factory.newDocumentBuilder().parse(
					new File(filename));
			return doc;
		} catch (SAXException e) {
			// A parsing error occurred; the xml input is not valid
		} catch (ParserConfigurationException e) {
		} catch (IOException e) {
		}
		return null;
	}

	public static void save(Document doc){
		try {
			Transformer transformer = TransformerFactory
					.newInstance().newTransformer();
			transformer.setOutputProperty(OutputKeys.INDENT, "yes");
			StreamResult result = new StreamResult(new FileWriter(
					"C:\\Output.xml"));
			DOMSource source = new DOMSource(doc);
			transformer.transform(source, result);
			System.out.println("File saved!");

		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}

But somehow,still I just won´t get it to work correctly.The save-operation won´t even be triggered and I haven´t figured out yet,if the overwriting mechanism works...
Maybe,now,it´s easier to see the problem for one of you?
Meanwhile,should I find the solution,I´ll post it right here

[Paul Clapham]

Okay. So line 12 says you start with "replacementDoc". At line 13 you get all of the children of that document's document node. If one of those children has a node name which matches what you're looking for (line 19) then you attempt to replace that child by this expression:

entireDoc.importNode(replacementDoc.getDocumentElement(), true)

Right so far?

Well, first of all there is no point in importing into the entireDoc document, since that isn't the one you're working with. You're working with replacementDoc (see line 12). So all you need there is this:

replacementDoc.getDocumentElement()

But now this can't work because you're trying to move the document element to be a child of itself.