How to import a string with nodes in an existing xml file using Xstream?

Question

My problem is the following. I have properties and parameters that a user can add and change. I have managed to create the new xml structure using Xstream. But now I want to import the new xml that is all stored in a String variable into my old xml file in a certain location. How Can I do this?

The Xml stored in a String that i want to import :

<param>
  <PARAMETER>nidRB</PARAMETER>
  <DATA__TYPE>String</DATA__TYPE>
  <DESCRIPTION>A nice feature</DESCRIPTION>
  <MIN__NO>1</MIN__NO>
  <MAX__NO>1</MAX__NO>
  <ORDER1>1</ORDER1>
  <NESTED>0</NESTED>
  <DEFAULT1>NULL</DEFAULT1>
  <FORMAT>NULL</FORMAT>
</param>

the xml structure is the following :

<root>
<info>
</info>
  <type>
    <Object_type>blabla</Object_Type>
       <prop>
          <blab>...</blab>
        </prop>
       <param>
           <blab>...</blab>
        </param>
        <restri>
        </restri>
     <Object_type>blabla</Object_Type>
       <prop>
          <blab>...</blab>
        </prop>
        <param>
           <blab>...</blab>
        </param>
        <restri>
        </restri>
  <Object_type>blabla</Object_Type>
       <prop>
          <blab>...</blab>
        </prop>


      New XML DATA Inserted here

         <restri>
        </restri>
   </type>
</root>

I cant really find any method in the Xstream documentation that performs this.

Ive tried this but its not XStream so i cant use it.

Update : 

I am using this code :

public void buildNewFile() {

        XStream xstream = new XStream(new DomDriver());

        String myBigDocument = getRootFile();
        String myImportDocument = getNewContent();
        Type rootObject = (Type) xstream.fromXML(myBigDocument);
        Parameters param = (Parameters) xstream.fromXML(myImportDocument);

        Type type = (Type) rootObject.getTypes().get(0);

        type.setParam(param);

        String mergedXml = xstream.toXML(rootObject);
        System.out.println(mergedXml);
    }

    public String getRootFile() {

        String text = "";
        File file = new File("type.xml");
        try {
            Scanner scanner = new Scanner(file);

            while (scanner.hasNext()) {

                text = scanner.nextLine();

            }

        } catch (FileNotFoundException e) {

            e.printStackTrace();
        }

        return text;

    }

    public String getNewContent() {

        String text = "";
        File file = new File("param.xml");
        try {
            Scanner scanner = new Scanner(file);

            while (scanner.hasNext()) {

                text = scanner.nextLine();

            }

        } catch (FileNotFoundException e) {

            e.printStackTrace();
        }

        return text;

    }

And it gives me this error :

[Fatal Error] :1:2: The markup in the document preceding the root element must be well-formed.
Exception in thread "main" com.thoughtworks.xstream.io.StreamException:  : The markup in the document preceding the root element must be well-formed.
    at com.thoughtworks.xstream.io.xml.DomDriver.createReader(DomDriver.java:105)
    at com.thoughtworks.xstream.io.xml.DomDriver.createReader(DomDriver.java:77)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1012)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1003)
    at 
xmleditor.service.CreateNewXMLData.buildNewFile(CreateNewXMLData.java:77)
    xmleditor.domain.Main.main(Main.java:10)
Caused by: org.xml.sax.SAXParseException: The markup in the document preceding the root element must be well-formed.
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source)
    at com.thoughtworks.xstream.io.xml.DomDriver.createReader(DomDriver.java:98)
    ... 5 more

Answer 1

Well, XStream is all about mapping XML to Java objects and back again.

So to solve you problem either

• merge the XML documents first (like with using XSLT) and read it then via XStream to have Java objects or do it the other way around
• read the two files to have to object structures and then use Java to set one object as the child of one other

The 2nd approach should be easier if you are already a bit comfortable with XStream and Java I guess.

So you 1st need something like this (in Java pseudo code):

String myBigDocument; // Or provide XStream with a Reader on the input file or whereever you get the data from.
String myImportDocument;
Root rootObject = XStream.fromXml(myBigDocument);
Param param = XStream.fromXml(myImportDocument);
// now search the fitting element in your Root object and assign the parameter
// I just select the 1st object from your types, you'll have to do this with the fitting one.
Type type = rootObject.getInfo().getType().get(0);

// Now set the child object
type.setParam(param);

// Now convert back to XML if you need that.
String mergedXml = XStream.toXml(rootObject);