精确字符串 coldfusion 正则表达式

Question

我正在使用正则表达式来替换所有不等于确切单词 "NULL" 的字符，并保留所有数字。我做了第一步，将我的字符串中的所有 "NULL" 个单词替换为：

<cfset data = ReReplaceNoCase("123NjyfjUghfLL|NULL|NULL|NULL","\bNULL\b","","ALL")>

它会删除所有 "NULL" 单词的实例，这意味着它不会从子字符串“123NjyfjUghfLL”中删除字母 "N"、"U" 和 "L"。这是正确的。但现在，我想扭转这一局面。我只想保留 "NULL" 个词，这意味着它会删除单个 "L"、"U" 和 "L"。所以我试过了：

<cfset data = ReReplaceNoCase("123NjyfjUghfLL|NULL|NULL|NULL","[^\bNULL\b]","","ALL")>

但现在这会保留所有 "N"、"U" 和 "L" 字母，因此它会输出 "NULLNULLNULLNULL"。应该只有3次"NULL".

有人可以帮我解决这个问题吗？在哪里添加额外的代码来保留数字？谢谢。

Answer 1

你可以做到这一点

<cfset data = ReReplaceNoCase("123NjyfjUghfLL|NULL|NULL|NULL","(^|\|)(?!NULL(?:$|\|))([^|]*)(?=$|\|)","","ALL")>

(^|\|)(?!NULL(?:$|\|))([^|]*)(?=$|\|)

解释：

 (                   # Opens Capture Group 1
     ^               # Anchors to the beginning to the string.
 |                   # Alternation (CG1)
     \|              # Literal |
 )                   # Closes CG1
 (?!                 # Opens Negative Lookahead
     NULL            # Literal NULL
     (?:             # Opens Non-Capturing group
         $           # Anchors to the end to the string.
     |               # Alternation (NCG)
         \|          # Literal |
     )               # Closes NCG
 )                   # Closes NLA
 (                   # Opens Capture Group 2
     [^|]*           # Negated Character class (excludes the characters within)
                       # None of: |
                       # * repeats zero or more times
 )                   # Closes CG2
 (?=                 # Opens LA
     $               # Anchors to the end to the string.
 |                   # Alternation (LA)
     \|              # Literal |
 )                   # Closes LA

Regex101.com demo

最后，对性格的一些感悟类（方括号内的内容）

[^\bNULL\b]的意思是

 [^\bNULL\b]     # Negated Character class (excludes the characters within)
                   # None of: \b,N,U,L
                   # When \b is inside a character class, it matches a backspace character.
                   # Outside of a character class, \b matches a word boundary as you use it in your first code.

字符类不是为匹配或忽略单词而设计的，它们是为允许或排除字符或字符范围而设计的。

编辑：

Ok so it works well. But what if I would like to keep also the digits? I am a kind of lost in this line of code and I cannot find where to put extra code... I think the extra code would be [^0-9] right?

这个正则表达式 (demo) 还允许任何长度的数字，其中数字是整个值

(^|\|)(?!(?:NULL|[0-9]+)(?:$|\|))([^|]*)(?=$|\|)

您也可以使用此正则表达式 (demo) 来允许带有十进制值的数字。

(^|\|)(?!(?:NULL|[0-9]+(?:\.[0-9]+)?)(?:$|\|))([^|]*)(?=$|\|)

精确字符串 coldfusion 正则表达式

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