I have this function in my code base, this should work for you.

public static Document loadXMLFromString(String xml) throws Exception
{
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    InputSource is = new InputSource(new StringReader(xml));
    return builder.parse(is);
}

also see this similar question

Using JDOM:

String xml = "<message>HELLO!</message>";
org.jdom.input.SAXBuilder saxBuilder = new SAXBuilder();
try {
    org.jdom.Document doc = saxBuilder.build(new StringReader(xml));
    String message = doc.getRootElement().getText();
    System.out.println(message);
} catch (JDOMException e) {
    // handle JDOMException
} catch (IOException e) {
    // handle IOException
}

Using the Xerces DOMParser:

String xml = "<message>HELLO!</message>";
DOMParser parser = new DOMParser();
try {
    parser.parse(new InputSource(new java.io.StringReader(xml)));
    Document doc = parser.getDocument();
    String message = doc.getDocumentElement().getTextContent();
    System.out.println(message);
} catch (SAXException e) {
    // handle SAXException 
} catch (IOException e) {
    // handle IOException 
}

Using the JAXP interfaces:

String xml = "<message>HELLO!</message>";
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = null;
try {
    db = dbf.newDocumentBuilder();
    InputSource is = new InputSource();
    is.setCharacterStream(new StringReader(xml));
    try {
        Document doc = db.parse(is);
        String message = doc.getDocumentElement().getTextContent();
        System.out.println(message);
    } catch (SAXException e) {
        // handle SAXException
    } catch (IOException e) {
        // handle IOException
    }
} catch (ParserConfigurationException e1) {
    // handle ParserConfigurationException
}