xmerl_xpath
% it is possible to write XSLT like transforms in Erlang.
%
% XSLT stylesheets are often used when transforming XML % documents, to other XML documents or (X)HTML for presentation. % XSLT contains quite many % functions and learning them all may take some effort. % This document assumes a basic level of % understanding of XSLT. %
%Since XSLT is based on a functional programming approach % with pattern matching and recursion it is possible to write % similar style sheets in Erlang. At least for basic % transforms. This % document describes how to use the XPath implementation together % with Erlangs pattern matching and a couple of functions to write % XSLT like transforms.
%This approach is probably easier for an Erlanger but % if you need to use real XSLT stylesheets in order to "comply to % the standard" there is an adapter available to the Sablotron % XSLT package which is written i C++. % See also the Tutorial. %
-module(xmerl_xs). -export([xslapply/2, value_of/1, select/2, built_in_rules/2 ]). -include("xmerl.hrl"). %% @spec xslapply(Function, EList::list()) -> List %% Function = () -> list() %% @doc xslapply is a wrapper to make things look similar to %% xsl:apply-templates. %% %%Example, original XSLT:
%% <xsl:template match="doc/title"> %% <h1> %% <xsl:apply-templates/> %% </h1> %% </xsl:template> %%%% %%
becomes in Erlang:
%% template(E = #xmlElement{ parents=[{'doc',_}|_], name='title'}) ->
%% ["<h1>",
%% xslapply(fun template/1, E),
%% "</h1>"];
%%
xslapply(Fun, EList) when is_list(EList) ->
lists:map( Fun, EList);
xslapply(Fun, E = #xmlElement{})->
lists:map( Fun, E#xmlElement.content).
%% @spec value_of(E) -> List
%% E = unknown()
%%
%% @doc Concatenates all text nodes within the tree.
%%
%% Example:
%% <xsl:template match="title"> %% <div align="center"> %% <h1><xsl:value-of select="." /></h1> %% </div> %% </xsl:template> %%%% %%
becomes:
%% template(E = #xmlElement{name='title'}) ->
%% ["<div align="center"><h1>",
%% value_of(select(".", E)), "</h1></div>"]
%%
value_of(E)->
lists:reverse(xmerl_lib:foldxml(fun value_of1/2, [], E)).
value_of1(#xmlText{}=T1, Accu)->
[xmerl_lib:export_text(T1#xmlText.value)|Accu];
value_of1(_, Accu) ->
Accu.
%% @spec select(String::string(),E)-> E
%%
%% @doc Extracts the nodes from the xml tree according to XPath.
%% @see value_of/1
select(Str,E)->
xmerl_xpath:string(Str,E).
%% @spec built_in_rules(Fun, E) -> List
%%
%% @doc The default fallback behaviour. Template funs should end with:
%% template(E) -> built_in_rules(fun template/1, E).
built_in_rules(Fun, E = #xmlElement{})->
lists:map(Fun, E#xmlElement.content);
built_in_rules(_Fun, E = #xmlText{}) ->
xmerl_lib:export_text(E#xmlText.value);
built_in_rules(_Fun, E = #xmlAttribute{}) ->
E#xmlAttribute.value;
built_in_rules(_Fun, _E) ->[].