Erlang的Xml解析-白红宇

Erlang的Xml解析

阅读量：2058 次

发布时间：2019-04-29

本文共 2878 字，大约阅读时间需要 9 分钟。

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：

[plain]

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,root,[],

{xmlNamespace,[],[]},

[],1,[],

[{xmlText,[{root,1}],1,[],"123",text}],

[],"/mnt/hgfs/work/myErlangWork/myErlang1/src",undeclared},

[]}

3> xmerl_xpath:string("/root",Doc).

[{xmlElement,root,root,[],

{xmlNamespace,[],[]},

[],1,[],

[{xmlText,[{root,1}],1,[],"123",text}],

[],"/mnt/hgfs/work/myErlangWork/myErlang1/src",undeclared}]

4> xmerl_xpath:string("/root/text()",Doc).

[{xmlText,[{root,1}],1,[],"123",text}]

举例：解析购物清单

shopping.xml

[plain]

<?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

[plain]

-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",Item),

Price = list_to_float(PriceString),

Quantity = list_to_integer(QuantityString),

Total + Price * Quantity

end,

0,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",XmlDoc),

ItemList = lists:foldl(fun(Item,Result)->

[#xmlText{value=Value}] = xmerl_xpath:string("/item/text()",Item),

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,

[],Items),

io:format("ItemList is ~p~n",[ItemList]),

ItemList.

执行：

[plain]

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"]

["bread","milk"]

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