Update XML, insert an element.

[Ahmad Sakhi]

Hi all,

I am trying add an element into an XML file. At the bottom is my input XML and desired output.
Input#1 is the original XML file.
Output#1 is my desired output.

Here's my code and it throws error at line [120]

 private static void addRow(Document doc) {
    	NodeList rows = doc.getElementsByTagName("row");
    	
    	for (int i=0; i < rows.getLength(); i++) {
    		String rName = rows.item(i).getAttributes().getNamedItem("name").toString();
        	
        	String task = "";
        	if (rName.contains("Engineering")) {
        		System.out.println("Step is : " + rName);
        	} else if (rName.contains("Inspection")) {
        		System.out.println("Step is: " + rName);
        		task = "Inspection";
        	}
        	
        	NodeList ents = rows.item(i).getChildNodes();
        	String colId = "";
        	int k = 0;
        	for (k=0; k < ents.getLength(); k++) {
        	
        		if (ents.item(k).getNodeName().equalsIgnoreCase("entries")) {
        			NodeList  ent = rows.item(i).getChildNodes();
        			
        			for (int j=0; j < ent.getLength(); j++) {
	        			if (ent.item(j).getNodeName().startsWith("entries")){
	        				NodeList  item = ent.item(j).getChildNodes();
	        				for (int p=0; p < item.getLength(); p++) {
		        				if (!item.item(p).getNodeName().startsWith("#")) {
				        			colId = item.item(p).getAttributes().getNamedItem("column_reference").toString();				        			
		        				}
	        				}
	        			}
        			}
                    colId = colId.substring(21, colId.length()-1);
                    int ncolId = Integer.parseInt(colId);
                    String sncolId = "col" + ++ncolId;
                    
                    Element newEnt = doc.createElement("entry");
                    newEnt.setAttribute("column_reference", sncolId);
                    
                    Element n = doc.createElement("task");
                    n.setTextContent(task);
                    Element e = doc.createElement("delivery");
                    e.setTextContent("");
                    
                    newEnt.appendChild(n);
                    newEnt.appendChild(e);
                    
                    ent.item(ent.getLength()-1).appendChild(newEnt);       // <-- This is line thorws exception 			
        		}
        	}
    	}
    }

ERROR

Exception in thread "main" org.w3c.dom.DOMException: HIERARCHY_REQUEST_ERR: An attempt was made to insert a node where it is not permitted. 
	at com.sun.org.apache.xerces.internal.dom.NodeImpl.insertBefore(Unknown Source)
	at com.sun.org.apache.xerces.internal.dom.NodeImpl.appendChild(Unknown Source)
	at com.util.vendm.distmat.UpdateXML.addRow(UpdateXML.java:120)
	at com.util.vendm.distmat.UpdateXML.main(UpdateXML.java:45)

Input XML
<distribution_rows>    <row name="Engineering" conditions_watermark="0" id="row3">      <conditions/>      <entries>        <entry column_reference="col3">          <task>Engineering</task>          <delivery></delivery>        </entry>        <entry column_reference="col5">          <task></task>          <delivery></delivery>        </entry>        <entry column_reference="col6">          <task>Engineering</task>          <delivery></delivery>        </entry>      </entries>    </row>    <row name="Inspection" conditions_watermark="0" id="row4">      <conditions/>      <entries>        <entry column_reference="col3">          <task></task>          <delivery></delivery>        </entry>        <entry column_reference="col5">          <task>Inspection</task>          <delivery></delivery>        </entry>        <entry column_reference="col6">          <task></task>          <delivery></delivery>        </entry>      </entries>    </row> </distribution_rows>

Desired output Basically I want to append the col7 nodes for each <entry> elements.
<distribution_rows> <row name="Engineering" conditions_watermark="0" id="row3"> <conditions></conditions> <entries> <entry column_reference="col3"> <task>Engineering</task> <delivery></delivery> </entry> <entry column_reference="col5"> <task></task> <delivery></delivery> </entry> <entry column_reference="col6"> <task>Engineering</task> <delivery></delivery> </entry> <entry column_reference="col7"> <task></task> <delivery></delivery> </entry> </entries> </row> <row name="Inspection" conditions_watermark="0" id="row4"> <conditions></conditions> <entries> <entry column_reference="col3"> <task></task> <delivery></delivery> </entry> <entry column_reference="col5"> <task>Inspection</task> <delivery></delivery> </entry> <entry column_reference="col6"> <task></task> <delivery></delivery> </entry> <entry column_reference="col7"> <task>Inspection</task> <delivery></delivery> </entry> </entries> </row> </distribution_rows>

[Paul Clapham]

In the XML you posted, an <entries> element has seven children. There are three <entry> elements and four white-space text elements; you may not have been aware of the latter. It looks to me like your code tries to add the new <entry> element as a child of the last of those seven elements, which is whitespace text. Text elements can't have children.

You need to add the new <entry> element as a new child of the <entries> element. You might also want to add another whitespace text element to make the resulting XML look nice, but don't do that until you are told to do so, as it doesn't change the meaning of the document.

[g tsuji]

[1] Line #21

                   //NodeList  ent = rows.item(i).getChildNodes();
                   NodeList  ent = rows.item(k).getChildNodes();

[2] Lines #23-32

                   for (int j=0; j < ent.getLength(); j++) {
                       if (ent.item(j).getNodeName().startsWith("entries")){
                           /* This looping is incorrect.
                           NodeList  item = ent.item(j).getChildNodes();
                           for (int p=0; p < item.getLength(); p++) {
                               if (!item.item(p).getNodeName().startsWith("#")) {
                                   colId = item.item(p).getAttributes().getNamedItem("column_reference").toString();
                               }
                           }
                          */
                         //just place this here
                       colId = item.item(j).getAttributes().getNamedItem("column_reference").toString();
                       }
                   }

The loop j may be better used by reversing order of the index and coupled it with "break" for the first match. But this is only a detail you have to consider rewriting everywhere.

[3] The main error asked. It is an misunderstanding of appendChild(). Line #48

                   //ent.item(ent.getLength()-1).appendChild(newEnt);       // <-- This is line thorws exception
                   ents.item(k).appendChild(newEnt);

[4] On the whole, the code does not give enough credit to java's DOM model. If you use DOM to flatten the xml tree using getChildNodes(), it is far away to use the more pertinent method getElementsByTagName() on the child Element everywhere. For instance, line #35

//NodeList ents = rows.item(i).getChildNodes();
NodeList ents = ((Element)rows.item(i)).getElementsByTagName("entry");

The coding inside would have to be rewritten. It would be greatly simplified and more focused.., eliminating a lot of checking...