Error deserializing json array nullpointer exception

Question

I receive this json through a request

{"pay_CCIban":"XXX",
"pay_bic":"YYY",
"pay_names[]":["name one","name two"],
"pay_extid":"extId"}

I'm trying to deserialize it with this class

global class Famrs{
    global class datajsonweb{
       global String pay_CCIban {get; set;}
       global String pay_bic {get; set;}
       global List<String> pay_names {get; set;}
       global String pay_extid {get; set;}
    }
    datajsonweb data = (datajsonweb)JSON.deserialize(requestBody.toString(),datajsonweb.class);
    Integer lstSize = data.pay_names.size(); //I get nullpointer here
    ...
}

I get an attempt to de-reference null object when I try to get the size of the array inside the json, i don't know what I'm doing wrong

Any help?

Thanks in advance

EDIT:

Like sfdcfox says, the "pay_names[]" key in the json needs to be like "pay_names" so I'm trying to do a replaceAll('[]','') but I'm getting: Invalid regex: Unclosed character class. If I try to escape the brackets I get: Illegal string literal.

Is it possible to remove the brackets in the json?

Thanks again

EDIT 2:

Thanks to Jesse Milburn's comment it works.

Answer 1

The [] in your JSON won't work. The parser would try to map this to an apex variable named pay_names[]. This is not a valid Apex identifier. Valid identifiers in Apex must start with a letter, can only include letters, numbers, and underscores, can't have two consecutive underscores, and can't be certain reserved keywords. JSON.deserialize does not automatically map things like [] to the nearest valid identifier.

In order to use a JSON class, your JSON would need to be:

{"pay_CCIban":"XXX",
"pay_bic":"YYY",
"pay_names":["name one","name two"],
"pay_extid":"extId"}

If you want to use the JSON exactly as is, use an explicit parser, or use JSON.deserializeUntyped, or JSON.Parser.