Allowed values for RequestParam in get url

Question

Is it possible to set possible values for @RequestParam(value = "id") String id)
?

The ideal is: I give some List<String> allowedValues and it automatically validate it. (This list will be loaded from database).

Answer 1

use an enum instead of a String and define your enum values

@RequestMapping(value = "yourRestEndPoint", method = RequestMethod.GET)
public anyReturnType methodName(@RequestParam(defaultValue = "ONE") IdValue id) {
 ....
}

and have a separate class defined e.g

public enum IdValue {
  ONE, TWO, THREE
} 

Answer 2

It is possible but not some magical way but by simple Validation checks.

Eg:

@RequestMapping(value = "yourRestEndPoint", method = RequestMethod.GET)
public anyReturnType methodName(@RequestParam(value = "id") String id){

     List<String> allowedValues = getAllowedValuesFromDB();

     if(allowedValues.contains(id)){//check if incoming ID belongs to Allowed Values
     //Do your action....
     }
}

private List<String> getAllowedValuesFromDB(){

    List<String> allowedValues = new ArrayList<>();
    //fetch list from DB
    //set fetched values to above List

    return allowedValues;
}

Second Way

If you want to do it like we do Bean Validation, using @Valid, which is for Bean not just a single parameter and also required Validator to be configured, then check out this & this answer.

Hope this helps.