Spring MVC + RequestParam as Map + get URL array parameters not working
arrays, dynamic, list, parameters, spring-mvc
Solution
When you request a `Map` annotated with `@RequestParam` Spring creates a map containing all request parameter name/value pairs. If there are two pairs with the same name, then only one can be in the map. So it's essentially a `Map<String, String>`
You can access all parameters through a `MultiValueMap`:
public String processGetRequest(@RequestParam MultiValueMap parameters) {
This map is essentially a `Map<String, List<String>>`. So parameters with the same name would be in the same list.
Problem
I'm currently working on an API controller. This controller should be able to catch any - unknown - parameter and put it in a `Map` object. Now I'm using this code to catch all parameters and put them in a `Map` ``` public String processGetRequest(final @RequestParam Map params) ``` Now the url I call is as follows: ``` server/api.json?action=doSaveDeck&Card_IDS[]=1&Card_IDS[]=2&Card_IDS[]=3 ``` Then I print out the parameters, for debugging purposes, with this piece of code: ``` if (logger.isDebugEnabled()) { for (Object objKey : params.keySet()) { logger.debug(objKey.toString() + ": " + params.get(objKey)); } } ``` The result of that is: ``` 10:43:01,224 DEBUG ApiRequests:79 - action: doSaveDeck 10:43:01,226 DEBUG ApiRequests:79 - Card_IDS[]: 1 ``` But the expected result should be something like: ``` 10:43:XX DEBUG ApiRequests:79 - action: doSaveDeck 10:43:XX DEBUG ApiRequests:79 - Card_IDS[]: 1 10:43:XX DEBUG ApiRequests:79 - Card_IDS[]: 2 10:43:XX DEBUG ApiRequests:79 - Card_IDS[]: 3 ``` Or atleast tell me that the Card_IDS is an `String[] / List<String>` and therefore should be casted. I also tried casting the parameter to a `List<String>` manually but that does not work either: ``` for (Object objKey : params.keySet()) { if(objKey.equals(NameConfiguration.PARAM_NAME_CARDIDS)){ //Never reaches this part List<String> ids = (List<String>)params.get(objKey); for(String id : ids){ logger.debug("Card: " + id); } } else { logger.debug(objKey + ": " + params.get(objKey)); } } ``` Could someone tell me how to get the array `Card_IDS` - It must be dynamically - from the `Map params` by using the `NameConfiguration.PARAM_NAME_CARDIDS`?