If I have header name value pair such as:

accept-encoding: gzip, deflate, br
:authority: stackoverflow.com
something: some:value

How do I only split after the header name? Meaning, following would be my results:

accept-encoding => gzip, deflate, br
:authority => stackoverflow.com
something => some:value

I have tried str.Split(":", 2) but it doesn't handle the :authority header

CodePudding user response：

You can split with : that is preceded with a word char and not followed with a word char:

str.split("\\b:\\B")

See the regex demo. Alternatively, you may split with : that is preceded with a non-whitespace char and is followed with a whitespace:

str.split("(?<=\\S):(?=\\s)")

See this regex demo.

Details:

• \b:\B - a word boundary (\b) requires a letter, digit or _ to appear immediately to the left of the : (as : is a non-word char) and the next non-word boundary \B requires a non-word char (any char other than letter, digit or underscore) to appear immediately on the right, or end of string can occur there, too
• (?<=\S) - a positive lookbehind that matches a location immediately preceded with a non-whitespace char
• (?=\s) - a positive lookahead that matches a location immediately followed with a whitespace char.

CodePudding user response：

If you only want to split on the first occurrence of : and allow an optional : at the start of the string, you could also make use of a lookbehind with a finite quantifier in Java {0,n} where n in this example is 100

(?<=^:?[^:\r\n]{0,100}):

In Java

str.Split("(?<=^:?[^:\\r\\n]{0,100}):")

• (?<= Postive lookbehind
  • ^:?[^:]{0,100} From the start of the string, match an optional : and 0-n occurrences of any char except : or a newline
• ) Close the lookbehind
• : Match the colon to split on

Regex demo