Erlang xml到元组和列表 [英] Erlang xml to tuples and lists

问题描述

我非常高兴能够开始我的erlang旅程，但是我已经停留了几天了，我开始害怕我不会满足我的截止日期。

我正在尝试从xml创建关键的值对元组。我想从任何嵌套的xml中列出一个列表。这似乎是一件非常常见的事情，但我找不到任何例子。

例如：

 < something> 
< Item> 
< name> The Name！< / name> 
<评论> 
< review> 
< review-by> WE< / review-by> 
< review-points> 92< / review-points> 
< / review> 
 
< review> 
< review-by> WS< / review-by> 
< review-points> 90< / review-points> 
< / review> 
< / reviews> 
< / Item> 
< / something> 
  

应该如下：

  [[{name，The Name！}，{review，[{review-by，WE}，{review-points，92} ，{review-by，WS}，{review-points，90}]]]] 
  

其中每个项目是主要的包装节点。

我承认货物被装载并调整了下面的代码。它只返回第一个Item的元素的列表。我不知道如何开始嵌套的。

非常感谢！

  -module（reader）。 
 -compile（export_all）。 
 -include_lib（xmerl / include / xmerl.hrl）。 
 
 parse（FileName） - > 
 {Records，_} = xmerl_scan：file（FileName），
 extract（Records，[]）。 
 
 extract（Record，Acc）when is_record（Record，xmlElement） - > 
 case Record＃xmlElement.name 
'Item' - > 
 ItemData = lists：foldl（fun extract / 2，[]，Record＃xmlElement.content），
 [{item，ItemData} | Acc]; 
 _  - > 
列表：foldl（fun extract / 2，Acc，Record＃xmlElement.content）
 end; 
 
 extract（{xmlText，[{Attribute，_}，{'Item'，2}，_]，_，_，Value，text}，Acc） - > 
 [{Attribute，Value} | Acc]; 
 
提取（_，Acc） - > 
加
  

解决方案

给 Erlsom 尝试。函数erlsom：simple_form（XML）将给你{Node，Attrib，Value}：

  {something []，
 [{Item，[]，
 [{name，[]，[The Name！]}，
 {评论 
 [{review，[]，
 [{review，[]，[WE]}，{review-points，[]，[92] }]}，
 {review，[]，
 [{review-by，[]，[WS]}，{review-points，[]， 90]}]}]}]}}} 
  

但是，如果要删除属性那么你可以写一个乐趣传递给erlsom SAX解析器或重新格式化simple_form的输出。这样的东西（重新格式化输出）：

  -module（reader）。 
 -compile（export_all）。 
 
 convert（XML） - > 
 case erlsom：
 {ok，{Node，_Attrib，Value}，_}的simple_form（XML） 
 {Node，xml_to_kv（Value）}; 
 Err-> 
 Err 
结束。 
 
 
 xml_to_kv（[{Node，_Attrib，Value} | T]） - > 
 [{Node，lists：flatten（xml_to_kv（Value））} | xml_to_kv（T）]; 
 
 xml_to_kv（Value） - > 
价值。 
  

这将产生以下输出：

  {something，
 [{Item，
 [{name，The Name！}，
 {评论 ，
 [{review，[{review-by，WE}，{review-points，92}]}，
 {review，[{评论，WS}，{review-points，90}]}]}]}}} 
  

注意，我没有在非常大的XML文件上测试这个。您应该运行几个测试并考虑mem问题。

I'm very excited to be starting my erlang journey, but I've been stuck on this for a few days now and I'm starting to get scared I won't meet my deadline.

I'm trying to create key, value pair tuples out of xml. I'd like to make a list out of any nested xml. It seems like a very common thing to do, but I can't find any examples.

For instance:

    <something>
        <Item>
            <name>The Name!</name>
            <reviews>
                    <review>
                        <review-by>WE</review-by>
                        <review-points>92</review-points>
                    </review>

                    <review>
                        <review-by>WS</review-by>
                        <review-points>90</review-points>
                    </review>
            </reviews>
        </Item>
    </something>

Should turn out like:

    [[{"name", "The Name!"}, {"reviews", [{"review-by", "WE"}, {"review-points", 92}], {"review-by", "WS"}, {"review-points", 90}]} ]]

Where each Item is the main wrapper node.

I've admittedly cargo culted and tweaked the code below. It only returns a list of the first Item's elements. And I'm not sure how to begin the nested ones.

Thanks so much!

    -module(reader).
    -compile(export_all).
    -include_lib("xmerl/include/xmerl.hrl").

    parse(FileName) ->
        {Records,_} = xmerl_scan:file(FileName),
        extract(Records, []).

    extract(Record, Acc) when is_record(Record, xmlElement) ->
        case Record#xmlElement.name of
            'Item' ->
                ItemData = lists:foldl(fun extract/2, [], Record#xmlElement.content),
                [ {item, ItemData} | Acc ];
            _ ->
                lists:foldl(fun extract/2, Acc, Record#xmlElement.content)
        end;

    extract({xmlText, [{Attribute, _}, {'Item', 2}, _], _, _, Value, text}, Acc) ->
        [{Attribute, Value}|Acc];

    extract(_, Acc) ->
        Acc.

解决方案

Give Erlsom a try. The Function "erlsom:simple_form(XML)" will give you {Node,Attrib,Value}:

  {"something",[],
 [{"Item",[],
   [{"name",[],["The Name!"]},
    {"reviews",[],
     [{"review",[],
       [{"review-by",[],["WE"]},{"review-points",[],["92"]}]},
      {"review",[],
       [{"review-by",[],["WS"]},{"review-points",[],["90"]}]}]}]}]}

However, if you want to drop the Attributes then you can write a fun to pass to the erlsom SAX parser or reformat the output of simple_form. Something like this (to reformat output):

-module(reader).
-compile(export_all).

convert(XML)->
    case erlsom:simple_form(XML) of
        {ok,{Node,_Attrib,Value},_}->
            {Node,xml_to_kv(Value)};
        Err->
            Err
    end.


xml_to_kv([{Node,_Attrib,Value}|T])->
    [{Node,lists:flatten(xml_to_kv(Value))}|xml_to_kv(T)];

xml_to_kv(Value)->
    Value.

This would produce the following output:

 {"something",
 [{"Item",
   [{"name","The Name!"},
    {"reviews",
     [{"review",[{"review-by","WE"},{"review-points","92"}]},
      {"review",[{"review-by","WS"},{"review-points","90"}]}]}]}]}

Note, I haven't tested this on very large XML files. You should run a few tests and consider mem issues.

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