使用 XPath 从参数映射构建 URL 查询字符串

Posted 2023-02-16

【中文标题】使用 XPath 从参数映射构建 URL 查询字符串

【英文标题】：Building a URL query string from a map of parameters with XPath

【发布时间】：2021-07-23 22:54:24

【问题描述】：

在 XSLT/XPath 3.0 中从 'param': 'value' 映射构建 URL 查询字符串的最易读的方法是什么？

【问题讨论】：

请注意——“最快”可能意味着运行速度最快。或者在编辑器中输入的最短时间（最简洁）。或者这需要最少的思考。相反，询问，什么是一种可读的方式来做到这一点。 （你用 local:build-uri() 得到的答案在这方面一点也不差）

另见反函数：***.com/questions/68944773/…

【参考方案1】：

以下功能将起作用：

declare function local:build-uri($base-uri as xs:string, $params as map(xs:string, xs:string)) as xs:string 
  if (map:size($params) ne 0) then
    let $param-string := string-join(
        map:keys($params)[. ne ""] ! (encode-for-uri(.) || "=" || encode-for-uri($params?(.))),
        "&"
      )
    return $base-uri || "?" || $param-string
  else
    $base-uri
;

例如：

declare namespace map = "http://www.w3.org/2005/xpath-functions/map";
declare variable $params := map 
  "one": "1",
  "two": "2",
  "three": "3",
  "four": "4"
;

local:build-uri("http://www.example.com", map),
local:build-uri("http://www.example.com", $params),
local:build-uri("", $params),
()

返回：

http://www.example.com
http://www.example.com?four=4&one=1&two=2&three=3
?four=4&one=1&two=2&three=3

编辑：为了支持多值参数（同时保持函数体与 XPath 兼容），这样的事情应该可以工作：

declare function local:build-uri(
  $base-uri as xs:string,
  $params as map(xs:string, xs:string*),
  $use-array-for-multivalue-params as xs:boolean (: param[]=value for php, etc. :)
) as xs:string 
  if (map:size($params) ne 0) then
    let $param-strings :=
      for $param in map:keys($params)[. ne '']
      return $params?($param) ! string-join((
        encode-for-uri($param),
        if ($use-array-for-multivalue-params and count($params?($param)) gt 1) then "[]" else "",
        "=",
        encode-for-uri(.)
      ), "")
    return $base-uri || "?" || string-join($param-strings, "&")
  else
    $base-uri
;

【讨论】：

如果有多个值的参数怎么办？ ;)

您确定这适用于多值参数吗？我得到了https://localhost:4443/?uri=https://dbpedia.org/resource/Copenhagen&mode=https://w3id.org/atomgraph/client#EditMode,https://w3id.org/atomgraph/client#ModalMode（URL 解码以提高可读性），而不是第二个mode 值用逗号连接。

【参考方案2】：

不短，也不一定容易理解。

但是

它处理空值（使用 csv 你会得到 key= 另一个完全省略键） 它处理 xs:anyAtomicType (xs:dateTime, xs:decimal, xs:boolean, ...) 添加了第三种常用方法来序列化查询字符串参数，其中多个值用逗号分隔

xquery version "3.1";


declare namespace qs="http://line-o.de/ns/qs";


(:~
 : Append nothing to names of parameters with multiple values 
 : ?single=v1&multi=v2&multi=v3 
 :)
declare function qs:serialize-query-string($parameters as map(xs:string, xs:anyAtomicType*)) as xs:string? 
  qs:serialize(
    $parameters,
    qs:serialize-parameter(?, ?, ()))
;

(:~
 : Append [] to names of parameters with multiple values 
 : ?single=v1&multi[]=v2&multi[]=v3 
 :)
declare function qs:serialize-query-string-array($parameters as map(xs:string, xs:anyAtomicType*)) as xs:string? 
  qs:serialize(
    $parameters,
    qs:serialize-parameter(?, ?, '[]'))
;

(:~
 : Commma separated values for parameters with multiple values 
 : ?single=v1&multi=v2,v3 
 :)
declare function qs:serialize-query-string-csv($parameters as map(xs:string, xs:anyAtomicType*)) as xs:string? 
  qs:serialize(
    $parameters,
    qs:serialize-parameter-csv#2)
;

declare function qs:serialize(
   $parameters as map(xs:string, xs:anyAtomicType*),
   $serializer as function(xs:string, xs:anyAtomicType*) as xs:string*
) as xs:string? 
    if (map:size($parameters) eq 0)
    then ()
    else
      $parameters
        => map:for-each($serializer)
        => string-join('&')
        => qs:prepend-questionmark()
;

declare function qs:serialize-parameter (
  $raw-parameter-name as xs:string,
  $values as xs:anyAtomicType*,
  $appendix as xs:string?
) as xs:string* 
    let $parameter-name := concat(
        encode-for-uri($raw-parameter-name),
        if (exists($values) and count($values)) then $appendix else ()
    )

    return
        for-each($values, 
            qs:serialize-parameter-value($parameter-name, ?))
;

declare function qs:serialize-parameter-csv ($raw-parameter-name as xs:string, $values as xs:anyAtomicType*) as xs:string* 
  concat(
    encode-for-uri($raw-parameter-name), 
    '=',
    $values
      => for-each(function ($value)  encode-for-uri(xs:string($value)) )
      => string-join(',')
  )
;

declare function qs:serialize-parameter-value (
  $parameter as xs:string, $value as xs:anyAtomicType
) as xs:string 
    ``[`$parameter`=`encode-for-uri($value)`]``
;

declare function qs:prepend-questionmark ($query-string as xs:string)  
  concat('?', $query-string)
;

qs:serialize-query-string(map),
qs:serialize-query-string-array(map),
qs:serialize-query-string-csv(map),
qs:serialize-query-string(map "a": ("b0","b1"), "b": "$=@#'" ),
qs:serialize-query-string-array(map "a": (xs:date("1970-01-01"),"b1"), "b": "$=@#'" ),
qs:serialize-query-string-csv(map "a": ("b0",3.14), "b": "$=@#'" ),
qs:serialize-query-string(map "a": ("b0","b1"), "c": () ),
qs:serialize-query-string-array(map "a": ("b0","b1"), "c": () ),
qs:serialize-query-string-csv(map "a": ("b0","b1"), "c": () )

以下是将上述内容拆分为模块和测试的要点：

https://gist.github.com/line-o/e492401494a4e003bb01b7a2f884b027

编辑：减少代码重复

【参考方案3】：

let 
   $encode-parameters-for-uri:= function($parameters as map(*)) as xs:string? 
      let 
         (: serialize each map entry :)
         $encoded-parameters:= map:for-each(
            $parameters,
            function ($key, $values) 
               (: serialize the sequence of values for this key :)
               for $value in $values return 
                  encode-for-uri($key) || '=' || encode-for-uri($value)
            
         ),
         (: join the URI parameters with ampersands :)
         $parameters-string:= string-join(
            $encoded-parameters,
            codepoints-to-string(38)
         )
      return
         (: prepend '?' if parameters exist :)
         if ($parameters-string) then
            '?' || $parameters-string
         else
            ()
   
return
   $encode-parameters-for-uri(
      map
         'size': 'large',
         'flavour': ('chocolate', 'strawberry')
      
   )

结果：?flavour=chocolate&flavour=strawberry&size=large

更简洁的版本，不同之处在于它将空映射转换为零长度字符串而不是空字符串序列：

let 
   $encode-parameters-for-uri:= function($parameters as map(*)) as xs:string 
      if (map:size($parameters)) then
         '?' || string-join(
            map:for-each(
               $parameters,
               function ($key, $values) 
                  for $value in $values return 
                     encode-for-uri($key) || '=' || encode-for-uri($value)
               
            ),
            codepoints-to-string(38)
         )
      else
         ''
   
return
   $encode-parameters-for-uri(
      map
      'foo': ('bar', 'baz'), 'direction': 'north'
      
   )

结果?direction=north&foo=bar&foo=baz