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For example,I want to generate the following xml file by using java with DOM

 <catalogue>
    <books>
        <book id="1">
           <name>Gone with the wind</name>
            <quantity>2</quantity>
        </book>
        <book id="2">
           <name>Call of the wind</name>
           <quantity>3</quantity>
         </book>
         <book id="3">
           <quality>Good</quality>
          </book>
    </books>
    </catalogue>

It's not very difficult to produce xml file with only 1 node named book, but with more than 1 with the same name, I dont know how to do it? I got the error:

Duplicate local variable

This is one part of my java code: I tried to create the first book element with the code:

  Element book = doc.createElement("book");
  rootElement.appendChild(book);

  Element name = doc.createElement("name");
  name.appendChild(doc.createTextNode("Gone with the wind"));
  book.appendChild(name);

And then I used the same code to create the second and the third book element, and I found the error. Is there any other way to do it? Can anyone give me a suggestion please? Thank you very much for your time

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  • 4
    Can you show us the code where you are getting that error? As far as valid XML goes, it looks correct, so I don't know why you would be getting that error without seeing the Java code. Commented Jan 4, 2011 at 22:37
  • Actually I dont have much experience in Java. I used: Element book = doc.createElement("book") to create the first book element and when I used the same code to generate another book node it made the error. I thought of for loop but I dont know how to deal with child node. Thank you for quick response Commented Jan 4, 2011 at 22:40
  • Have you looked at reading the XML to see what DOM is produced? You should be able to look at the DOM in the debugger. Commented Jan 4, 2011 at 22:42
  • 1
    @user: Again: Can you show the code where you're getting that error? It's probably pretty straightforward, but without showing it to us, we can't help you. (There's this handy "edit" link under the question...) Commented Jan 4, 2011 at 22:45
  • The ord.w3c DOM API is a pig. If you're going to be doing DOM manipulation like this, I suggest using something a bit more user-friendly, like JDOM, XOM or Dom4j Commented Jan 4, 2011 at 22:55

2 Answers 2

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2

I'm guessing you are appending the same object twice. You need to call createElement each time.

This won't work

    Element name = doc.createElement("name");
    name.appendChild(doc.createTextNode("Gone with the wind"));
    book.appendChild(name);

    name.appendChild(doc.createTextNode("Call of the wind"));
    book.appendChild(name);

You need to do

    Element name = doc.createElement("name");
    name.appendChild(doc.createTextNode("Gone with the wind"));
    book.appendChild(name);

    name = doc.createElement("name");
    name.appendChild(doc.createTextNode("Call of the wind"));
    book.appendChild(name);

Complete example

     Document doc = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();

    Element root = doc.createElement("catalogue");
    doc.appendChild(root);

    Element books = doc.createElement("books");
    root.appendChild(books);

    Element book1 = doc.createElement("book");
    book1.setAttribute("id", "1");
    books.appendChild(book1);

    Element book1_name = doc.createElement("name");
    book1_name.setTextContent("Gone with the wind");
    book1.appendChild(book1_name);

    Element book1_quantity = doc.createElement("quantity");
    book1_quantity.setTextContent("2");
    book1.appendChild(book1_quantity);

    Element book2 = doc.createElement("book");
    book2.setAttribute("id", "2");
    books.appendChild(book2);

    Element book2_name = doc.createElement("name");
    book2_name.setTextContent("Call of the wind");
    book2.appendChild(book2_name);

    Element book2_quantity = doc.createElement("quantity");
    book2_quantity.setTextContent("3");
    book2.appendChild(book2_quantity);

    Element book3 = doc.createElement("book");
    book3.setAttribute("id", "3");
    books.appendChild(book3);

    Element book3_quality = doc.createElement("quality");
    book3_quality.setTextContent("Good");
    book3.appendChild(book3_quality);
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1 Comment

Thank Andrew, looking at your code I find myself stupid really. Thanks very much again
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If the problem is this, then you've declared multiple local variables with the same name. In all programmling languages, you can only have one variable with the same name declared in the same scope. A scope is usually enclosed by curly braces. You can use the same variable name in the same method if you indent them with additional scopes, e.g. like the example below.

However, you should think about the naming of your variables, or if you should instead make use of loop statements. You could also number your variables, e.g. name1, name2, name3 etc.

alt text

If you really want to have multiple variables with the same name, you can separate them by unnamed code blocks by just using the curly braces like this:

Element book = doc.createElement("book");
rootElement.appendChild(book);

{
  Element name = doc.createElement("name");
  name.appendChild(doc.createTextNode("Gone with the wind"));
  book.appendChild(name);
}
{
  Element name = doc.createElement("name");
  name.appendChild(doc.createTextNode("Call of the wind"));
  book.appendChild(name);
}
...

Both name variables life in seprate scopes, so they don't interfere with each other and will not lead to the "Duplicate local variable name" compiler error message.

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1 Comment

Thank you I think it must be useful

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