Regular expression in Java to match a String containing + character

Question

I'm using annotation javax.validation.constraints.Pattern to validate the sort parameter. The value of this parameter must be: +id or +originId for ascending, and -id or -originId for descending.

The syntax of this parameter can not be modified.

@Valid @Pattern(regexp= SORT_REGEXP, message = SORT + NOT_VALID) @RequestParam(name = SORT, required = false) String sort,

This is what I have as my regular expression:

^[+-]id$|^[+-]originId$

I have also tried escaping the plus sign + like:

^[\\+-]id$|^[\\+-]originId$

If I use the -id or the -originId, it's been validated but when I use the + it says that it's not matching the pattern.

How to match the plus-sign with a regular expression?

the regular expression seems to be working: ideone.com/oMPWM8 - we need more information — user16320675
– user16320675, Commented Nov 22, 2022 at 15:44
Related question using asc and desc instead of mathematical signs: Spring Data Rest - Sort by multiple properties - Stack Overflow — hc_dev
– hc_dev, Commented Dec 6, 2022 at 19:59
Within URLs the + is usually decoded to space: url - Why is Spring de-coding + (the plus character) on application/json get requests? and what should I do about it?. See also "Requires URL percent encoding" for Lucene-syntax in Paging, sorting, filtering and retrieving specific fields in your RESTful API | by Guillaume Viguier-Just | Medium — hc_dev
– hc_dev, Commented Dec 6, 2022 at 20:10

Brett Ryan · Accepted Answer · 2022-11-22 11:40:45Z

1

Your pattern can be simplified by specifying the boundaries outside your match and using a group.

^[+-](id|originId)$

answered Nov 22, 2022 at 11:40

Brett Ryan

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5 Comments

Gonzalo Over a year ago

Thanks for your improvement suggestion! Any idea of how to solve the issue with the + character?

Brett Ryan Over a year ago

This should solve the issue with the + character. Tested with Pattern.compile("^[+-](id|originId)$").matcher("+id")

Gonzalo Over a year ago

I'm sorry, but if I try to send the request with +id and using that regex is still saying that doesn't match. I know it should work but is failing...

Alex Sveshnikov Over a year ago

The regex is good, the problem is elsewhere. How do you send a request? Remember, that for example in an url a simple plus character is interpreted as a space and should be escaped as %2B

Gonzalo Over a year ago

Thanks Alex! That was the problem. I try with %2B instead of + and works.

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