Question

In Java:
Suppose I have 3 xml files

<student>lin</student> --  file1.xml

<student>Eric</student> --  file2.xml

<student>joe</student> --  file3.xml

How can I merge these xml’s (considering that they don’t have the DTD or namespace declaration) to create

<class><student>lin</student> <student>Eric</student>
<student>joe</student> </class> -- file4.xml

class being the wrapping node I supply manually

Ps: I used xstream to create the xml’s

Answer 1

I your files are large I would use a SAXParser where your ContentHandler would echo the tags and the content.

Something like (pseudo-code):

print("<class>")
foreach(file in files)
  {
  mysaxparser.parse(new Handler() 
     {
     content="";

     void endElement(tag)
         {
          if(tag.equals("student")) print("<student>"+escapeXML(content)+"</student>"); 
         content="";
         }
     void characters(str)
         {
         content+=str;
         }
     },file);
  }
print("</class>");

If your files are small enough to fit into the memory: load the DOM of each document using a DocumentBuilder and call importNode to merge the documents into one.