Erlang的Xml解析常用函数：
xmerl_scan库：
string(Text::list()) -> {xmlElement(),Rest}
Parse string containing an XML document,将字符串列表，解析成XML树
file(Filename::string()) -> {xmlElement(),Rest} Parse file containing an XML document
xmerl_xpath库：
string(Str,Doc) -> [docEntity()] | Scalar 根据XPath，从已经解析好的XML树中提取出节点
基础练习：
1> Xml="<?xml version='1.0' encoding='utf-8'?><root>123</root>".
"<?xml version='1.0' encoding='utf-8'?><root>123</root>"
2> {Doc,_}=xmerl_scan:string(Xml).
{{xmlElement,root,[],{xmlNamespace,[]},1,[{xmlText,[{root,1}],"123",text}],"/mnt/hgfs/work/myErlangWork/myErlang1/src",undeclared},[]}
3> xmerl_xpath:string("/root",Doc).
[{xmlElement,undeclared}]
4> xmerl_xpath:string("/root/text()",Doc).
[{xmlText,text}]
举例：解析购物清单
shopping.xml
<?xml version="1.0" encoding="UTF-8"?>
<shopping>
<item name="bread" quantity="3" price="2.50">bread</item>
<item name="milk" quantity="2" price="3.50">milk</item>
</shopping>
xml_test.erl
-module(xml_test).
-include_lib("xmerl/include/xmerl.hrl").
-export([
test_xml/0,test_xml_file/0
]).
%%读取xml列表为xmlElement，然后解析数据
test_xml() ->
Xml = "<shopping>
<item name=\"bread\" quantity=\"3\" price=\"2.50\">bread</item>
<item name=\"milk\" quantity=\"2\" price=\"3.50\">milk</item>
</shopping>",{XmlDoc,_} = xmerl_scan:string(Xml),get_total(XmlDoc),get_item_text(XmlDoc).
%%Parse file containing an XML document，然后解析数据
test_xml_file() ->
{Doc,_} = xmerl_scan:file("shopping.xml",[{encoding,'utf-8'}]),get_total(Doc),get_item_text(Doc).
%%计算得到购物清单的总金额
get_total(XmlDoc) ->
Items = xmerl_xpath:string("/shopping/item",XmlDoc),TotalPrice = lists:foldl(fun(Item,Total)->
[#xmlAttribute{value=PriceString}] = xmerl_xpath:string("/item/@price",Item),[#xmlAttribute{value=QuantityString}] = xmerl_xpath:string("/item/@quantity",Price = list_to_float(PriceString),Quantity = list_to_integer(QuantityString),Total + Price * Quantity
end,Items),io:format("Price of shopping is $~.2f~n",[TotalPrice]),TotalPrice.
%%获取购物清单上所有商品内容的列表，取item节点的text
get_item_text(XmlDoc) ->
Items = xmerl_xpath:string("/shopping/item",ItemList = lists:foldl(fun(Item,Result)->
[#xmlText{value=Value}] = xmerl_xpath:string("/item/text()",io:format("item is ~p~n",[Value]),Result ++ [Value] %% 结果是["bread","milk"]
%% 此句如果改为Result ++ Value 结果就变成了"breadmilk"
end,io:format("ItemList is ~p~n",[ItemList]),ItemList.
执行：
1> c(xml_test).
{ok,xml_test}
2> xml_test:test_xml().
Price of shopping is $14.50
item is "bread"
item is "milk"
ItemList is ["bread","milk"]
["bread","milk"]
3> xml_test:test_xml_file().
Price of shopping is $14.50
item is "bread"
item is "milk"
ItemList is ["bread","milk"]
