erlang mysql结果到xml

Question

我有一个输出：

MysqlResult = {selected,["id","first_name","last_name"],
         [{1,"Matt","Williamson"},
         {2,"Matt","Williamson2"}]}

如何使其看起来像：

XML = "
 <result id='1'>
 <first_name>Matt</first_name>
 <last_name>Williamson</last_name>
 </result>
 <result id='2'>
 <first_name>Matt</first_name>
 <last_name>Williamson2</last_name>
 </result>"

我正在寻找一种将其放入 IQ 中的智能方法（ejabberd）

IQ#iq{type = result, sub_el =
                   [{xmlelement, "result",
                   [{"xmlns", ?NS_NAMES}],
                   [{xmlelement, "userinfo", [],
                   [{xmlcdata,"???"??  }]}]}]}

Answer 1

首先从元组中提取结果元素：

{selected, _Columns, Results} = MysqlResult.

然后使用列表理解将其转换为 ejabberd 的内部 XML 格式：

XML = [{xmlelement, "result", [{"id", integer_to_list(Id)}],
        [{xmlelement, "first_name", [], [{xmlcdata, FirstName}]},
         {xmlelement, "last_name", [], [{xmlcdata, LastName}]}]}
       || {Id, FirstName, LastName} <- Results].

并将其插入到您的 IQ 记录中：（

IQ#iq{type = result, sub_el =
                   [{xmlelement, "result",
                   [{"xmlns", ?NS_NAMES}],
                   [{xmlelement, "userinfo", [],
                   XML}]}]}

假设您想要 元素作为 元素的子元素）

Answer 2

使用 xmerl 在 Erlang 中创建 XML：

1> MysqlResult = {selected,["id","first_name","last_name"],
1>          [{1,"Matt","Williamson"},
1>          {2,"Matt","Williamson2"}]}.
{selected,["id","first_name","last_name"],
          [{1,"Matt","Williamson"},{2,"Matt","Williamson2"}]}

2> {selected, _Columns, Results} = MysqlResult.
{selected,["id","first_name","last_name"],
          [{1,"Matt","Williamson"},{2,"Matt","Williamson2"}]}

3> Content = [{result, [{id, Id}], [{first_name, [First]}, {last_name, [Last]}]} || {Id, First, Last} <- Results].
[{result,[{id,1}],
         [{first_name,["Matt"]},{last_name,["Williamson"]}]},
 {result,[{id,2}],
         [{first_name,["Matt"]},{last_name,["Williamson2"]}]}]

4> xmerl:export_simple(, xmerl_xml).
["<?xml version=\"1.0\"?>",
 [[["<","result",[[" ","id","=\"","1","\""]],">"],
   [[["<","first_name",">"],["Matt"],["</","first_name",">"]],
    [["<","last_name",">"],
     ["Williamson"],
     ["</","last_name",">"]]],
   ["</","result",">"]],
  [["<","result",[[" ","id","=\"","2","\""]],">"],
  [[["<","first_name",">"],["Matt"],["</","first_name",">"]],
    [["<","last_name",">"],
     ["Williamson2"],
     ["</","last_name",">"]]],
   ["</","result",">"]]]]

5> io:format("~s", [v(-1)]).
<?xml version="1.0"?><result id="1"><first_name>Matt</first_name><last_name>Williamson</last_name></result><result id="2"><first_name>Matt</first_name><last_name>Williamson2</last_name></result>ok

Answer 3

尝试在 mysql 命令行客户端中使用 --xml 和 --execute 选项。

mysql客户端

Answer 4

xmerl 解决方案绝对没问题，如果这是一次性的事情，可能是可行的方法。

但是，如果您正在编写 xmpp 客户端，即使是一个简单的客户端，也可以考虑使用 exmpp - https://github.com/ processone/exmpp 。您可以使用一些策略来提取数据并生成 XML，但一般来说，辅助函数（最有可能在 exmpp_iq 和 exmpp_stanza 模块内）将非常方便。

exmpp 也不会去任何地方——ejabberd3 的 alpha 正在内部使用它（最终）