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xml2struct

xml2struct

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20 Aug 2010 (Updated )

Convert an xml file into a MATLAB structure for easy access to the data.

xml2struct( file )
function [ s ] = xml2struct( file )
%Convert xml file into a MATLAB structure
% [ s ] = xml2struct( file )
%
% A file containing:
% <XMLname attrib1="Some value">
%   <Element>Some text</Element>
%   <DifferentElement attrib2="2">Some more text</Element>
%   <DifferentElement attrib3="2" attrib4="1">Even more text</DifferentElement>
% </XMLname>
%
% Will produce:
% s.XMLname.Attributes.attrib1 = "Some value";
% s.XMLname.Element.Text = "Some text";
% s.XMLname.DifferentElement{1}.Attributes.attrib2 = "2";
% s.XMLname.DifferentElement{1}.Text = "Some more text";
% s.XMLname.DifferentElement{2}.Attributes.attrib3 = "2";
% s.XMLname.DifferentElement{2}.Attributes.attrib4 = "1";
% s.XMLname.DifferentElement{2}.Text = "Even more text";
%
% Please note that the following characters are substituted
% '-' by '_dash_', ':' by '_colon_' and '.' by '_dot_'
%
% Written by W. Falkena, ASTI, TUDelft, 21-08-2010
% Attribute parsing speed increased by 40% by A. Wanner, 14-6-2011
% Added CDATA support by I. Smirnov, 20-3-2012
%
% Modified by X. Mo, University of Wisconsin, 12-5-2012

    if (nargin < 1)
        clc;
        help xml2struct
        return
    end
    
    if isa(file, 'org.apache.xerces.dom.DeferredDocumentImpl') || isa(file, 'org.apache.xerces.dom.DeferredElementImpl')
        % input is a java xml object
        xDoc = file;
    else
        %check for existance
        if (exist(file,'file') == 0)
            %Perhaps the xml extension was omitted from the file name. Add the
            %extension and try again.
            if (isempty(strfind(file,'.xml')))
                file = [file '.xml'];
            end
            
            if (exist(file,'file') == 0)
                error(['The file ' file ' could not be found']);
            end
        end
        %read the xml file
        xDoc = xmlread(file);
    end
    
    %parse xDoc into a MATLAB structure
    s = parseChildNodes(xDoc);
    
end

% ----- Subfunction parseChildNodes -----
function [children,ptext,textflag] = parseChildNodes(theNode)
    % Recurse over node children.
    children = struct;
    ptext = struct; textflag = 'Text';
    if hasChildNodes(theNode)
        childNodes = getChildNodes(theNode);
        numChildNodes = getLength(childNodes);

        for count = 1:numChildNodes
            theChild = item(childNodes,count-1);
            [text,name,attr,childs,textflag] = getNodeData(theChild);
            
            if (~strcmp(name,'#text') && ~strcmp(name,'#comment') && ~strcmp(name,'#cdata_dash_section'))
                %XML allows the same elements to be defined multiple times,
                %put each in a different cell
                if (isfield(children,name))
                    if (~iscell(children.(name)))
                        %put existsing element into cell format
                        children.(name) = {children.(name)};
                    end
                    index = length(children.(name))+1;
                    %add new element
                    children.(name){index} = childs;
                    if(~isempty(fieldnames(text)))
                        children.(name){index} = text; 
                    end
                    if(~isempty(attr)) 
                        children.(name){index}.('Attributes') = attr; 
                    end
                else
                    %add previously unknown (new) element to the structure
                    children.(name) = childs;
                    if(~isempty(text) && ~isempty(fieldnames(text)))
                        children.(name) = text; 
                    end
                    if(~isempty(attr)) 
                        children.(name).('Attributes') = attr; 
                    end
                end
            else
                ptextflag = 'Text';
                if (strcmp(name, '#cdata_dash_section'))
                    ptextflag = 'CDATA';
                elseif (strcmp(name, '#comment'))
                    ptextflag = 'Comment';
                end
                
                %this is the text in an element (i.e., the parentNode) 
                if (~isempty(regexprep(text.(textflag),'[\s]*','')))
                    if (~isfield(ptext,ptextflag) || isempty(ptext.(ptextflag)))
                        ptext.(ptextflag) = text.(textflag);
                    else
                        %what to do when element data is as follows:
                        %<element>Text <!--Comment--> More text</element>
                        
                        %put the text in different cells:
                        % if (~iscell(ptext)) ptext = {ptext}; end
                        % ptext{length(ptext)+1} = text;
                        
                        %just append the text
                        ptext.(ptextflag) = [ptext.(ptextflag) text.(textflag)];
                    end
                end
            end
            
        end
    end
end

% ----- Subfunction getNodeData -----
function [text,name,attr,childs,textflag] = getNodeData(theNode)
    % Create structure of node info.
    
    %make sure name is allowed as structure name
    name = toCharArray(getNodeName(theNode))';
    name = strrep(name, '-', '_dash_');
    name = strrep(name, ':', '_colon_');
    name = strrep(name, '.', '_dot_');

    attr = parseAttributes(theNode);
    if (isempty(fieldnames(attr))) 
        attr = []; 
    end
    
    %parse child nodes
    [childs,text,textflag] = parseChildNodes(theNode);
    
    if (isempty(fieldnames(childs)) && isempty(fieldnames(text)))
        %get the data of any childless nodes
        % faster than if any(strcmp(methods(theNode), 'getData'))
        % no need to try-catch (?)
        % faster than text = char(getData(theNode));
        text.(textflag) = toCharArray(getTextContent(theNode))';
    end
    
end

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

    attributes = struct;
    if hasAttributes(theNode)
       theAttributes = getAttributes(theNode);
       numAttributes = getLength(theAttributes);

       for count = 1:numAttributes
            %attrib = item(theAttributes,count-1);
            %attr_name = regexprep(char(getName(attrib)),'[-:.]','_');
            %attributes.(attr_name) = char(getValue(attrib));

            %Suggestion of Adrian Wanner
            str = toCharArray(toString(item(theAttributes,count-1)))';
            k = strfind(str,'='); 
            attr_name = str(1:(k(1)-1));
            attr_name = strrep(attr_name, '-', '_dash_');
            attr_name = strrep(attr_name, ':', '_colon_');
            attr_name = strrep(attr_name, '.', '_dot_');
            attributes.(attr_name) = str((k(1)+2):(end-1));
       end
    end
end

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