Spring @RequestParam Map<String, String> does not work in POST method

Question

from the Spring documentation I took the following:

public @interface RequestParam

Annotation which indicates that a method parameter should be bound to a web request parameter. Supported for annotated handler methods in Servlet and Portlet environments.

...

If the method parameter is Map or MultiValueMap and a parameter name is not specified, then the map parameter is populated with all request parameter names and values.

Now I have created a controller for test purposes. It has a GET and a POST method and each uses a @RequestParam java.util.Map as only parameter. In the method body I am only trying to print the size of the map. When I send requests (GET/POST) only in the GET method the map contains any key/value pairs. I am using the Poster add-on in Firefox and I am sending three parameters.

import java.util.Map;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class TestController {

    @RequestMapping(value="test/method", method = RequestMethod.GET)
    @ResponseBody
    public String testmethodGet(@RequestParam Map<String, String> params) {

        System.out.println("GET: " + params.size()); // prints GET: 3   
        return "";

    }

    @RequestMapping(value="test/method", method = RequestMethod.POST)
    @ResponseBody
    public String testmethodPost(@RequestParam Map<String, String> params) {

        System.out.println("POST: " + params.size()); // prints POST: 0
        return "";

    }

}

Would any of you guys know why @RequestParam Map would not work with a POST request or whether I need to change something to make it work?

Thanks.

Answer 1

Actually, it works on GET and POST method. It was solely my fault. The initially given code will work, when you actually pass parameters to the POST request.

Consider the following JS ( jQuery ) code as how to send a valid request:

$.ajax({
    type: "POST",
    url: "test/method",
    data: { param1: param1, param2: param2, param3: param3 },
    success: function(data) {
        console.log("testPost successful!");
    },    
    dataType: "html", // expected return value type
    error: function(data, status, error) {
        console.log("testPost with errors!");
    }
});