Erlang解析xml

最近Erlang项目中有用到xml处理，简单研究了，主要查找erlang库中xmerl的初学文档（lib/xmerl-1.2.8/doc/html/xmerl_ug.html）。

并参考坚强2002的博客：http://www.cnblogs.com/me-sa/archive/2012/07/20/erlang_xml.html

废话不多说，上代码：

直接用官方给出的xml示例来处理（motorcycles.xml）：

 

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE motorcycles SYSTEM "motorcycles.dtd">
<motorcycles>
  <bike year="2000" color="black">
    <name>
      <manufacturer>Suzuki</manufacturer>
      <brandName>Suzuki VL 1500</brandName>
      <additionalName>Intruder</additionalName>
    </name>
    <engine>V-engine, 2-cylinders, 1500 cc</engine>
    <kind>custom</kind>
    <drive>cardan</drive>
    <accessories>Sissy bar, luggage carrier,V&amp;H exhaust pipes</accessories>
  </bike>
  <date>2004.08.25</date>
  <bike year="1983" color="read pearl">
    <name>
      <manufacturer>Yamaha</manufacturer>
      <brandName>XJ 400</brandName>
    </name>
    <engine>4 cylinder, 400 cc</engine>
    <kind>alround</kind>
    <drive>chain</drive>
    <comment>Good shape!</comment>
  </bike>
</motorcycles>

如果xmerl_scan:file("motorcycles.xml"),报错，则请删除xml文件中DTD声明或者使用

xmerl_scan:file("motorcycles.xml", [{validation,false}]),

 

%% 取xml中bike属性year
get_attr_val() ->
 {Result, _Rest} = xmerl_scan:file("motorcycles.xml"),
 Years = xmerl_xpath:string("bike/@year", Result),
 io:format("Format=====Years=====~p~n", [Years]),
 lists:foldl(fun(K, Acc) ->
     #xmlAttribute{value=Val} = K,
     [{"year", Val}|Acc] end, [], Years).

执行结果：[{"year","1983"},{"year","2000"}]

     
%% 取xml中date值
get_xml_date() ->
 {Result, _Rest} = xmerl_scan:file("motorcycles.xml"),
 Date = xmerl_xpath:string("date", Result),
 [#xmlElement{content = Content}] = Date,
 [#xmlText{value = Val}] = Content,
 {"date", Val}.

执行结果：{"date","2004.08.25"}
 
%% 取xml中name节点下manufacturer的值
get_xml_names() ->
 {Result, _Rest} = xmerl_scan:file("motorcycles.xml"),
 Bikes = xmerl_xpath:string("bike", Result),
 NameVals = lists:foldl(fun(K, Acc) ->
     Name = xmerl_xpath:string("name/manufacturer", K),
     [#xmlElement{content = [#xmlText{value = Val}]}] = Name,
     [{"manufacturer", Val}|Acc] end, [], Bikes),
 lists:reverse(NameVals).
 
执行结果：[{"manufacturer","Suzuki"},{"manufacturer","Yamaha"}]

%% 转换xml
gen_xml_list() ->
 XmlData = {bike, [{year,"2003"},{color,"black"},{condition,"new"}],
          [{name, [{manufacturer,["Harley Davidsson"]},
                 {brandName,["XL1200C"]},
                 {additionalName,["Sportster"]}]},
           {engine, ["V-engine, 2-cylinders, 1200 cc"]},
           {kind,["custom"]},
           {drive,["belt"]}]},
 XmlLists = xmerl:export_simple([XmlData],xmerl_xml),
 lists:flatten(XmlLists).
 
执行结果："<?xml version=\"1.0\"?><bike year=\"2003\" color=\"black\" condition=\"new\">
<name><manufacturer>Harley Davidsson</manufacturer><brandName>XL1200C</brandName>
<additionalName>Sportster</additionalName></name><engine>V-engine, 2-cylinders, 1200 cc</engine>
<kind>custom</kind><drive>belt</drive></bike>"