How to pass list parameters for each object using

Question

I am using Spring MVC RequestMapping here for GET parameters. Below is my code -

@RequestMapping(value = "index", method = RequestMethod.GET)
public HashMap<String, String> handleRequest(@RequestParam("dc1Servers") String dc1Servers, @RequestParam("dc2Servers") String dc2Servers, @RequestParam("dc3Servers") String dc3Servers) {
    HashMap<String, String> model = new HashMap<String, String>();
    String helloWorld = "Hello World!";
    model.put("greeting", helloWorld);

    System.out.println(dc1Servers);
    System.out.println(dc2Servers);
    System.out.println(dc3Servers);

    return model;
}

I am hitting this URL - http://127.0.0.1:8080/dataweb/index?dc1Servers=3&dc2Servers=3&dc3Servers=3 then it goes into the above code and prints out 3 on the console for all the print and works fine.

Now if you see, I have dc1, dc2 and dc3.

So for dc1, I would like to send these in the URL as the parameters-

dc1Servers=3

dc1HostA
dc1HostB
dc1HostC

dc1IPAddresssA
dc1IPAddresssB
dc1IPAddresssC

Similarly for dc2, I would like to send these in the URL as the parameters-

dc2Servers=3

dc2HostA
dc2HostB
dc2HostC

dc2IPAddresssA
dc2IPAddresssB
dc2IPAddresssC

Similarly for dc3, I would like to send these in the URL as the parameters-

dc3Servers=3

dc3HostA
dc3HostB
dc3HostC

dc3IPAddresssA
dc3IPAddresssB
dc3IPAddresssC  

Now I am not sure how would I construct an URL for this use case and how would my method will look like? I would like to send them in one single URL call.

Is this use case possible to do using Spring MVC?

Answer 1

You could pass the parameters any way you see fit, one way is to pass them by their natural grouping like this: http://127.0.0.1:8080/dataweb/index?dc1Server=dc1HostA,dc1IPAddressA&dc1Server=dcHostB,dc1IPAddressB....

By using the same parameter name for each group you'd need to use a MultiValueMap. A MultiValueMap is more or less a Map<String, List<String>>, so parameters with the same name(dc1Server, dc2Server, etc) would be in the same list. You would use this to get a full list of the params you passed in like this:

public HashMap<String, String> handleRequest(@RequestParam MultiValueMap<String,String> allRequestParams) 

Then you'd have 3 keys, dc1Server would contain all the dc1Server data, dc2Server all the dc2Server etc

Could look into using @ModelAttribute if you want to do direct mapping to domain objects: Link

EDIT

public void testSpringMultiValueMap() {
        MultiValueMap<String, String> map = new LinkedMultiValueMap<String, String>();
        map.add("dc1Server", "dc1HostA,dc1IPAddressA");
        map.add("dc1Server", "dc1HostB,dc1IPAddressB");
        map.add("dc1Server", "dc1HostC,dc1IPAddressC");
        map.add("dc2Server", "dc2HostA,dc2IPAddressA");
        map.add("dc2Server", "dc2HostB,dc2IPAddressB");
        map.add("dc2Server", "dc2HostC,dc2IPAddressC");

        List<String> dc1List = map.get("dc1Server");

        for(String pair: dc1List) {
            String[] tokens = pair.split(",");
            System.out.println("host: " + tokens[0] + " ip: " + tokens[1]);
        }
    }

Answer 2

Url parameters are strings, so your options for passing a variable number of strings are:

Encode your values in a single url parameter

The simplest way is to use delimiter characters if you know your values will never contain them. Given you're trying to pass ip addresses and host names, this should work for you: &dc1Servers=dc1HostA,dc1IPAddressA,dc1HostB,dc1IPAddressB, etc.

Pass the same url parameter multiple times

Put the @RequestParam annotation on a method arg of type String[], and pass that url parameter multiple times: &dc1Host=dc1HostA&dc1IPAddress=dc1IPAddressA&dc1Host=dc1HostB&dc1IPAddress=dc1IPAddressB, etc.

Here are some more details on this approach: How to pass post array parameter in Spring MVC