Export a Document Object Model to an XML File

You can export a Document Object Model (DOM) document node to an XML file by using a matlab.io.xml.dom.DOMWriter object or the xmlwrite function.

The matlab.io.xml.dom.DOMWriter class belongs to the MATLAB^® API for XML Processing (MAXP). To use a MAXP DOMWriter object, represent a DOM document node as a matlab.io.xml.dom.Document object. To create and add elements, text, and other nodes to the document node, use MAXP classes and methods. See matlab.io.xml.dom. You do not need Java^® software to use MAXP classes.

To create a DOM document that you can write by using xmlwrite, use com.mathworks.xml.XMLUtils.createDocument. To create and add nodes to the document node, use methods of the Java API for XML Processing (JAXP). See the org.w3c.dom package description at https://docs.oracle.com/javase/7/docs/api.

Create a DOM Document

Common steps for creating an XML document include:

1. Create a document node and define the root element. This code creates a document node by creating a MAXP matlab.io.xml.dom.Document object:

   import matlab.io.xml.dom.*
   docNode = Document('root_element');

   This code creates a document node that you can use with JAXP methods:

   docNode = com.mathworks.xml.XMLUtils.createDocument('root_element');

2. Get the node that corresponds to the root element by calling getDocumentElement. The root element node is required to add child nodes.

3. Add element, text, comment, and attribute nodes by calling methods of the document node. Useful methods include:

   • createElement

   • createTextNode

   • createComment

   • setAttribute

4. To append child nodes to a parent node, use appendChild.

   Tip

   Text nodes are always children of element nodes. To add a text node, use createTextNode with the document node, and then use appendChild with the parent element node.

Write a DOM Document Node to an XML File Using a MAXP DOMWriter Object

This example uses a matlab.io.xml.dom.DOMWriter object to create an info.xml file for the Upslope Area Toolbox, which is described in Display Custom Documentation.

Create the document node and root element, toc.

import matlab.io.xml.dom.*
docNode = Document('toc');

Get the root element, and set the version attribute.

toc = docNode.getDocumentElement;
setAttribute(toc,'version','2.0');

Add the tocitem element node for the product page. Each tocitem element in this file has a target attribute and a child text node.

product = createElement(docNode,'tocitem');
setAttribute(product,'target','upslope_product_page.html');
appendChild(product,createTextNode(docNode,'Upslope Area Toolbox'));
appendChild(toc,product);

Add a comment.

appendChild(product,createComment(docNode,' Functions '));

Add a tocitem element node for each function.

functions = {'demFlow','facetFlow','flowMatrix','pixelFlow'};
n = numel(functions);
for idx = 1:n
    curr_node = createElement(docNode,'tocitem');
    curr_file = [functions{idx} '_help.html']; 
    setAttribute(curr_node,'target',curr_file);
    
    % Child text is the function name.
   appendChild(curr_node,createTextNode(docNode,functions{idx}));
    appendChild(product,curr_node);
end

Export the DOM node to info.xml, and view the file.

xmlFileName = 'info.xml';
writer = matlab.io.xml.dom.DOMWriter;
writer.Configuration.FormatPrettyPrint = true;

writeToFile(writer,docNode,xmlFileName);

type('info.xml');

<?xml version="1.0" encoding="UTF-8" standalone="no" ?>
<toc version="2.0">

  <tocitem target="upslope_product_page.html">Upslope Area Toolbox
    <!-- Functions -->
    <tocitem target="demFlow_help.html">demFlow</tocitem>
    <tocitem target="facetFlow_help.html">facetFlow</tocitem>
    <tocitem target="flowMatrix_help.html">flowMatrix</tocitem>
    <tocitem target="pixelFlow_help.html">pixelFlow</tocitem>
  </tocitem>

</toc>

Write a DOM Document Node to an XML File Using xmlwrite

This example uses xmlwrite to create an info.xml file for the Upslope Area Toolbox, which is described in Display Custom Documentation.

docNode = com.mathworks.xml.XMLUtils.createDocument('toc');
toc = docNode.getDocumentElement;
toc.setAttribute('version','2.0');
product = docNode.createElement('tocitem');
product.setAttribute('target','upslope_product_page.html');
product.appendChild(docNode.createTextNode('Upslope Area Toolbox'));
toc.appendChild(product)
product.appendChild(docNode.createComment(' Functions '));
functions = {'demFlow','facetFlow','flowMatrix','pixelFlow'};
for idx = 1:numel(functions)
    curr_node = docNode.createElement('tocitem');
    
    curr_file = [functions{idx} '_help.html']; 
    curr_node.setAttribute('target',curr_file);
    
    % Child text is the function name.
    curr_node.appendChild(docNode.createTextNode(functions{idx}));
    product.appendChild(curr_node);
end
xmlwrite('info.xml',docNode);
type('info.xml');

<?xml version="1.0" encoding="utf-8"?>
<toc version="2.0">
   <tocitem target="upslope_product_page.html">Upslope Area Toolbox<!-- Functions --><tocitem target="demFlow_help.html">demFlow</tocitem>
      <tocitem target="facetFlow_help.html">facetFlow</tocitem>
      <tocitem target="flowMatrix_help.html">flowMatrix</tocitem>
      <tocitem target="pixelFlow_help.html">pixelFlow</tocitem>
   </tocitem>
</toc>

Update an Existing XML File

To change data in an existing file:

1. Import the file into a DOM document node by using a matlab.io.xml.dom.Parser object or xmlread.

2. Traverse the node and add or change data using methods, such as:

   • getElementsByTagName

   • getFirstChild

   • getNextSibling

   • getNodeName

   • getNodeType

   If you use matlab.io.xml.dom.Parser to read the XML file into a matlab.io.xml.dom.Document, use MATLAB API for XML Processing (MAXP) classes and methods. See matlab.io.xml.dom. If you use xmlread, use Java API for XML Processing (JAXP) methods. See the org.w3c.dom package description at https://docs.oracle.com/javase/7/docs/api.

3. When the DOM document contains all your changes, write the file. For a MAXP DOM document, use a matlab.io.xml.DOMWriter object. For a JAXP DOM document, use xmlwrite.