Parsing xml document in java

Question

I am trying to retrieve some data from xml document, but the program throws NullPointerException. This is the snippet of code:

     if("Success".equals(nodeValue))
     {

           NodeList productList = xmlDocument.getElementsByTagName("Products").item(0).getChildNodes(); // gets all childs of Product node
           for (int j = 0; j < productList.getLength(); j++)
           {
               singleProduct = xmlDocument.getElementsByTagName("Product").item(j).getChildNodes();

               for(int x = 0; x < singleProduct.getLength(); x++)
               {  
                   if(singleProduct.item(x).getNodeType() == Node.ELEMENT_NODE)
                   {
                   String nodeName = singleProduct.item(x).getNodeName();

                 String value = singleProduct.item(x).getChildNodes().item(0).getNodeValue();
                         System.err.println(x+" "+nodeName+" "+ value);
                     if ("ProductID".equals(nodeName))
                {

                    id.put(xx, value);
                        type.put(y, singleProduct.item(x).getChildNodes().item(1).getAttributes().getNamedItem("type").getTextContent());;
                    xx++;
                        y++;
                     }
                  }
               }
           }
     }

This part throws exception:

                 String value = singleProduct.item(x).getChildNodes().item(0).getNodeValue();

Exception is thrown due to the value of index inside item(0) method. How should I know the index of item in collection? I have similar program parsing XML document, it throws exception (NullPOinter) but still it runs because I catch exception. The same thing I am trying to do here, but the program does not work, terminates, though I catch Exception. How to extract correct index for item() method? Cheers

McDowell · Accepted Answer · 2011-04-02 12:58:04Z

4

getChildNodes().item(0)

getChildNodes() returns a NodeList; use this value and check that its length is greater than zero.

NullPointerExceptions are an indication of a programming error and should not be caught.

As an aside, you may want to look at the XPath API for extracting data from DOM trees.

answered Apr 2, 2011 at 12:58

McDowell

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2 Comments

ucas Over a year ago

I checked the length, it is 1. What are other thoughts?

McDowell Over a year ago

@ucas - it isn't obvious to me where the issue is based on the code sample. I can see some red flags - like calling xmlDocument.getElementsByTagName more than once, but without seeing a sample document and the ultimate goal, it is difficult to provide help.

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