问题
We are building an API in-house and often are passing a parameter with multiple values.
They use: mysite.com?id=1&id=2&id=3
Instead of: mysite.com?id=1,2,3
I favor the second approach but I was curious if it was actually incorrect to do the first?
回答1:
I'm not an HTTP guru, but from what I understand there's not a definitive standard on the query part of the URL regarding multiple values, it's typically up to the CGI that handles the request to parse the query string.
RFC 1738 section 3.3 mentions a searchpart and that it should go after the ? but doesn't seem to elaborate on its format.
http://<host>:<port>/<path>?<searchpart>
回答2:
I did not (bother to) check which RFC standard defines it. (Anyone who knows about this please leave a reference in the comment.) But in practice, the mysite.com?id=1&id=2&id=3 way is already how a browser would produce when a form contains duplicated fields, typically the checkboxes. See it in action in this w3schools example page. So there is a good chance that the whatever programming language you are using, already provides some helper functions to parse an input like that and probably returns a list.
You could, of course, go with your own approach such as mysite.com?id=1,2,3, which is not bad at all in this particular case. But you will need to implement your own logic to produce and to consume such format. Now you may or may not need to think about handling some corner cases by yourself, such as: what if the input is not well-formed, like mysite.com?id=1,2,? And do you need to invent yet another separator, if the comma sign itself can also be a valid input, like mysite.com?name=Doe,John|Doe,Jane? Would you reach to a point that you will use a json string as the value, like mysite.com?name=["John Doe", "Jane Doe"]? etc. etc.. Your mileage may vary.
回答3:
Worth adding that inconsistend handling of duplicate parameters in the URL on the server is may lead to vulnerabilities, specifically server-side HTTP parameter pollution, with a practical example - Client side Http Parameter Pollution - Yahoo! Classic Mail Video Poc.
回答4:
in your first approach you will get an array of querystring values but in second approach you will get a string of querystring values.
来源：https://stackoverflow.com/questions/11621477/using-duplicate-parameters-in-a-url