Creating a regular expression for a URI path

Question

I need to parse this String "/<productId>/save" and I have to ensure that productId is an unsigned integer of 32 bits.

Of course I could split the String using the character "/" and then in the returned array try to cast the product Id to an Integer and see if I get an exception or not, but it does not seem a very elegant solution.

Instead I've tried using this regular expression boolean match=path.matches("\\/\\d+\\/save"); which works fine but it is not respecting the restriction of the integer of 32 bits, basically I can enter a number of any size.

I.e the followinf string /44444444444444444/save"; matches the regular expression.

What is the more elegant way to do this? Could you recommend me any approach?

The most elegant way is clearly to not try to check the number with regex (it's possible but ugly and inefficient), so extract it and check it with a simple comparison. If you want you can limit the number of digits in the pattern. — Casimir et Hippolyte, Nov 30 '16 at 22:27
Duplicate of http://stackoverflow.com/questions/20793578/regex-for-a-valid-32-bit-signed-integer — 0xA2C2A, Nov 30 '16 at 22:28
RegEx can't be used to check integral bounds without some _really_ ugly regex. — Qix - MONICA WAS MISTREATED, Nov 30 '16 at 22:28
To give an idea, for a 8bits number you must write something like: `1[0-9]{0,2}|2(?:[0-4][0-9]?|5[0-5]?|[6-9])?|[3-9][0-9]?`, imagine the same for a 32bits number. — Casimir et Hippolyte, Nov 30 '16 at 22:36
but poster is also looking for the num in the middle of the URI pattern, so isn't the regex the best solution there? — badperson, Nov 30 '16 at 22:42
Ask yourself about the purpose of Url-Rewrites: It should make readable URLs - Search-Engine-Friendly (even if Search Engines don't care about it anyway). So, you'd better keep "abstract" information like ids out of this url: `http://mypage.com/action/save/?id=4444444444444444` Then - if your ID does not rely on regex, but the regular parameter-workflow, java should just convert it to long, float or whatever. Trying to handle "System-Limits" will just move the case towards the "next" limit without any real resolution of the actual problem. — dognose, Nov 30 '16 at 22:53

score 1 · Answer 1 · answered Nov 30 '16 at 22:33

Here's one solution that deals with the possibility the number is too large:

@Test
public void testMatchIntWithRegex() {
    String rgx = "\\/(\\d+)\\/save";
    String example = "/423/save";
    String exampleB = "/423666666666666666666666666666666666666666/save";

    Pattern p = Pattern.compile(rgx);
    Matcher m = p.matcher(example);
    if(m.find()){
        String sInt = m.group(1);
        try{
            int num = Integer.parseInt(sInt);
            System.out.println("num is : " + num);
        } catch(NumberFormatException e){
            e.printStackTrace();
        }


    }

}

example works while exampleB throws an exception

Creating a regular expression for a URI path

1 Answers1