xmlread (MATLAB Functions)

Parse XML document and return Document Object Model node

Syntax

```
DOMnode = xmlread(filename)
```

Description

DOMnode = xmlread(filename) reads a URL or filename and returns a Document Object Model node representing the parsed document. The node can be manipulated by using standard DOM functions.

A properly parsed document displays to the screen as

xDoc = xmlread(...)
xDoc =
    [#document: null]

Remarks

Find out more about the Document Object Model at the World Wide Web Consortium (W3C) Web site, http://www.w3.org/DOM/. For specific information on using Java DOM objects, visit the Sun Web site, http://www.java.sun.com/xml/docs/api.

Examples

Example 1

All XML files have a single root element. Some XML files declare a preferred schema file as an attribute of this element. Use the getAttribute method of the DOM node to get the name of the preferred schema file:

xDoc = xmlread(fullfile(matlabroot, ...
               'toolbox/matlab/general/info.xml'));

xRoot = xDoc.getDocumentElement;
schemaURL = ...
   char(xRoot.getAttribute('xsi:noNamespaceSchemaLocation'))

schemaURL =
   http://www.mathworks.com/namespace/info/v1/info.xsd

Example 2

Each info.xml file on the MATLAB path contains several listitem elements with a label and callback element. This script finds the callback that corresponds to the label 'Plot Tools':

infoLabel = 'Plot Tools';
infoCbk = '';
itemFound = false;

xDoc = xmlread(fullfile(matlabroot, ...
               'toolbox/matlab/general/info.xml'));

% Find a deep list of all listitem elements.
allListItems = xDoc.getElementsByTagName('listitem');

% Note that the item list index is zero-based.
for k = 0:allListItems.getLength-1
   thisListItem = allListItems.item(k);
   childNode = thisListItem.getFirstChild;
 
   while ~isempty(childNode)
      %Filter out text, comments, and processing instructions.
      if childNode.getNodeType == childNode.ELEMENT_NODE
         % Assume that each element has a single
         % org.w3c.dom.Text child.
         childText = char(childNode.getFirstChild.getData);

         switch char(childNode.getTagName)
         case 'label';
            itemFound = strcmp(childText, infoLabel);
         case 'callback' ;
            infoCbk = childText;
         end
      end  % End IF
      childNode = childNode.getNextSibling;
   end  % End WHILE

   if itemFound
      break;
   else
      infoCbk = '';
   end
end  % End FOR

disp(sprintf('Item "%s" has a callback of "%s".', ...
             infoLabel, infoCbk))

Example 3

This function parses an XML file using methods of the DOM node returned by xmlread, and stores the data it reads in the Name, Attributes, Data, and Children fields of a MATLAB structure:

function theStruct = parseXML(filename)
% PARSEXML Convert XML file to a MATLAB structure.
try
   tree = xmlread(filename);
catch
   error('Failed to read XML file %s.',filename);
end

% Recurse over child nodes. This could run into problems 
% with very deeply nested trees.
try
   theStruct = parseChildNodes(tree);
catch
   error('Unable to parse XML file %s.');
end


% ----- Subfunction PARSECHILDNODES -----
function children = parseChildNodes(theNode)
% Recurse over node children.
children = [];
if theNode.hasChildNodes
   childNodes = theNode.getChildNodes;
   numChildNodes = childNodes.getLength;
   allocCell = cell(1, numChildNodes);

   children = struct(             ...
      'Name', allocCell, 'Attributes', allocCell,    ...
      'Data', allocCell, 'Children', allocCell);

    for count = 1:numChildNodes
        theChild = childNodes.item(count-1);
        children(count) = makeStructFromNode(theChild);
    end
end

% ----- Subfunction MAKESTRUCTFROMNODE -----
function nodeStruct = makeStructFromNode(theNode)
% Create structure of node info.

nodeStruct = struct(                        ...
   'Name', char(theNode.getNodeName),       ...
   'Attributes', parseAttributes(theNode),  ...
   'Data', '',                              ...
   'Children', parseChildNodes(theNode));

if any(strcmp(methods(theNode), 'getData'))
   nodeStruct.Data = char(theNode.getData); 
else
   nodeStruct.Data = '';
end

% ----- Subfunction PARSEATTRIBUTES -----
function attributes = parseAttributes(theNode)
% Create attributes structure.

attributes = [];
if theNode.hasAttributes
   theAttributes = theNode.getAttributes;
   numAttributes = theAttributes.getLength;
   allocCell = cell(1, numAttributes);
   attributes = struct('Name', allocCell, 'Value', allocCell);

   for count = 1:numAttributes
      attrib = theAttributes.item(count-1);
      attributes(count).Name = char(attrib.getName);
      attributes(count).Value = char(attrib.getValue);
   end
end

See Also

xmlwrite, xslt

xlswrite xmlwrite