Java appending XML docs to existing docs

Question

I have two XML docs that I\'ve created and I want to combine these two inside of a new envelope. So I have

  National Weath         


        

Answer 1

It's a bit tricky, but the following example runs:

public static void main(String[] args) {

    DocumentImpl doc1 = new DocumentImpl();
    Element root1 = doc1.createElement("root1");
    Element node1 = doc1.createElement("node1");
    doc1.appendChild(root1);
    root1.appendChild(node1);

    DocumentImpl doc2 = new DocumentImpl();
    Element root2 = doc2.createElement("root2");
    Element node2 = doc2.createElement("node2");
    doc2.appendChild(root2);
    root2.appendChild(node2);

    DocumentImpl doc3 = new DocumentImpl();
    Element root3 = doc3.createElement("root3");
    doc3.appendChild(root3);

    // root3.appendChild(root1); // Doesn't work -> DOMException
    root3.appendChild(doc3.importNode(root1, true));

    // root3.appendChild(root2); // Doesn't work -> DOMException
    root3.appendChild(doc3.importNode(root2, true));   
}

Answer 2

I know you got the issue solved already, but I still wanted to take a stab at this problem using the XOM library that I'm currently testing out (related to this question), and while doing that, offer a different approach than that of Andreas_D's answer.

(To simplify this example, I put your <alert-set> and <weather-set> into separate files, which I read into nu.xom.Document instances.)

import nu.xom.*;

[...]

Builder builder = new Builder();
Document alertDoc = builder.build(new File("src/xomtest", "alertset.xml"));
Document weatherDoc = builder.build(new File("src/xomtest", "weatherset.xml"));
Document mainDoc = builder.build("<DataSet><blank/><blank/></DataSet>", "");

Element root = mainDoc.getRootElement();
root.replaceChild(
    root.getFirstChildElement("blank"), alertDoc.getRootElement().copy());
root.replaceChild(
    root.getFirstChildElement("blank"), weatherDoc.getRootElement().copy());

The key is to make a copy of the elements to be inserted into mainDoc; otherwise you'll get a complain that "child already has a parent".

Outputting mainDoc now gives:

<?xml version="1.0" encoding="UTF-8"?>
<DataSet>
    <alert-set>
        <warning>National Weather Service...</warning>
        <start-date>5/19/2009</start-date>
        <end-date>5/19/2009</end-date>
    </alert-set>
    <weather-set>
        <chance-of-rain type="percent">31</chance-of-rain>
        <conditions>Partly Cloudy</conditions>
        <temperature type="Fahrenheit">78</temperature>
    </weather-set>
</DataSet>

To my delight, this turned out to be very straight-forward to do with XOM. It only took a few minutes to write this, even though I'm definitely not very experienced with the library yet. (It would have been even easier without the <blank/> elements, i.e., starting with simply <DataSet></DataSet>.)

So, unless you have compelling reasons for using only the standard JDK tools, I warmly recommend trying out XOM as it can make XML handling in Java much more pleasant.