Question: How I can pass a Map parameter as a GET param in url to Spring REST controller ?

Answer: 
There are different ways (*but a simple `@RequestParam('myMap')Map<String,String>` does not work - maybe not true anymore!*)

The (IMHO) easiest solution is to use a command object then you could use `[key]` in the url to specifiy the map key:

@Controller

```
@RequestMapping("/demo")
public class DemoController {

    public static class Command{
        private Map<String, String> myMap;

        public Map<String, String> getMyMap() {return myMap;}
        public void setMyMap(Map<String, String> myMap) {this.myMap = myMap;}

        @Override
        public String toString() {
            return "Command [myMap=" + myMap + "]";
        }
    }

    @RequestMapping(method=RequestMethod.GET)
    public ModelAndView helloWorld(Command command) {
        System.out.println(command);
        return null;
    }
}

```

* Request: http://localhost:8080/demo?myMap[line1]=hello&myMap[line2]=world
* Output: `Command [myMap={line1=hello, line2=world}]`

*Tested with Spring Boot 1.2.7*
It’s possible to bind all request parameters in a Map just by adding a Map object after the annotation:

```
@RequestMapping("/demo")
public String example(@RequestParam Map<String, String> map){
    String apple = map.get("APPLE");//apple
    String banana = map.get("BANANA");//banana

    return apple + banana;
}

```

Request

> 
> /demo?APPLE=apple&BANANA=banana
> 
> 
> 

Source -- <https://reversecoding.net/spring-mvc-requestparam-binding-request-parameters/>