JDom not recognising all of XML - "No Doctype Declaration"

I am downloading data from Open Street maps and attempting to store it in an XML file.

The xml file is returned in the following format:

<?xml version="1.0" encoding="UTF-8"?>
<osm version="0.6" generator="CGImap 0.3.3 (21759 thorn-01.openstreetmap.org)"
    copyright="OpenStreetMap and contributors" attribution="http://ift.tt/ItuEqj"
    license="http://ift.tt/1oPTky1">
    <bounds minlat="52.4440800" minlon="-1.9305700" maxlat="52.4451000"
        maxlon="-1.9280700" />
    <node id="1" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="2" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="3" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="4" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="5" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="6" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="7" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
    <node id="8" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290400" />
            <node id="" visible="true" version="1" changeset="21443971"
        timestamp="2014-04-01T17:54:04Z" user="brianboru" uid="9065" lat="52.4424918"
        lon="-1.9290410" />

    <way id="5" visible="true" version="1" changeset="21222698"
        timestamp="2014-03-21T07:25:03Z" user="brianboru" uid="9065">
        <nd ref="1" />
        <nd ref="2" />
        <nd ref="4" />


        <tag k="addr:city" v="Birmingham" />
        <tag k="addr:housenumber" v="97" />
        <tag k="addr:postcode" v="B29 7DX" />
        <tag k="addr:street" v="Alton Road" />
        <tag k="building" v="terraced_house" />
        <tag k="source" v="bing" />
    </way>

    <way id="6" visible="true" version="1" changeset="21222698"
        timestamp="2014-03-21T07:25:03Z" user="brianboru" uid="9065">
        <nd ref="1" />
        <nd ref="2" />
        <nd ref="3" />
        <nd ref="6" />
        <nd ref="8" />


        <tag k="addr:city" v="Birmingham" />
        <tag k="addr:housenumber" v="97" />
        <tag k="addr:postcode" v="B29 7DX" />
        <tag k="addr:street" v="Alton Road" />
        <tag k="building" v="terraced_house" />
        <tag k="source" v="bing" />
    </way>

    <way id="7" visible="true" version="1" changeset="21222698"
        timestamp="2014-03-21T07:25:03Z" user="brianboru" uid="9065">
        <nd ref="1" />
        <nd ref="2" />
        <nd ref="4" />
        <nd ref="6" />
        <nd ref="8" />


        <tag k="addr:city" v="Birmingham" />
        <tag k="addr:housenumber" v="97" />
        <tag k="addr:postcode" v="B29 7DX" />
        <tag k="addr:street" v="Alton Road" />
        <tag k="building" v="terraced_house" />
        <tag k="source" v="bing" />
    </way>

    <way id="8" visible="true" version="1" changeset="21222698"
        timestamp="2014-03-21T07:25:03Z" user="brianboru" uid="9065">
        <nd ref="1" />
        <nd ref="2" />
        <nd ref="5" />
        <nd ref="7" />


        <tag k="addr:city" v="Birmingham" />
        <tag k="addr:housenumber" v="97" />
        <tag k="addr:postcode" v="B29 7DX" />
        <tag k="addr:street" v="Alton Road" />
        <tag k="building" v="terraced_house" />
        <tag k="source" v="bing" />
    </way>




</osm>

I have tested and can confirm the data is retrieved in this format as if I download it and write it line by line to file. However, I do not want to write to file and instead want to pass the XML document around my Java code. This is why I began using JDom.

I have the following code for using JDom to download this data and store

URL url = new URL("http://ift.tt/1ftwOtA");
    URLConnection conn = url.openConnection();

conn.setDoOutput(true);

OutputStreamWriter writer = new OutputStreamWriter(
        conn.getOutputStream());

writer.write(urlParameters);
writer.flush();
System.out.println("finshed downloading everything");

BufferedReader reader = new BufferedReader(new InputStreamReader(
        conn.getInputStream()));
System.out.println("read it all in ");

String line;

while ((line = reader.readLine()) != null) {
    responseBuilder.append(line + '\n');
}

System.out.println("finsined appending response");
SAXBuilder sb = new SAXBuilder();
System.out.println("Made sax  ");

Document d = null;
try {
    d = sb.build(new StringReader(responseBuilder.toString()));
    System.out.println("Built doc");

} catch (Exception e) {
    System.out.println(e);
}
writer.close();
reader.close();

}

When I call d.toString() I recieve the following error in my console:

[Document:  No DOCTYPE declaration, Root is [Element: <osm/>]]

If I call d.getContentSize() it returns 1.

Can anyone help me please? how do I get it to recognise the rest of the elements except the closing tag?

I am guessing this is because JDom perhaps needs a DTD to work? I wrote a osm.dtd and saved it in my project but am unsure how to load it. Any help or advice would be appreciated.