How to POST a JSON payload to a @RequestParam in Spring MVC

You can do this by registering a Converter from String to your parameter type using an auto-wired ObjectMapper:

import org.springframework.core.convert.converter.Converter;

@Component
public class PersonConverter implements Converter<String, Person> {

    private final ObjectMapper objectMapper;

    public PersonConverter (ObjectMapper objectMapper) {
        this.objectMapper = objectMapper;
    }

    @Override
    public Person convert(String source) {
        try {
            return objectMapper.readValue(source, Person.class);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

Yes,is possible to send both params and body with a post method: Example server side:

@RequestMapping(value ="test", method = RequestMethod.POST)
@ResponseStatus(HttpStatus.OK)
@ResponseBody
public Person updatePerson(@RequestParam("arg1") String arg1,
        @RequestParam("arg2") String arg2,
        @RequestBody Person input) throws IOException {
    System.out.println(arg1);
    System.out.println(arg2);
    input.setName("NewName");
    return input;
}

and on your client:

curl -H "Content-Type:application/json; charset=utf-8"
     -X POST
     'http://localhost:8080/smartface/api/email/test?arg1=ffdfa&arg2=test2'
     -d '{"name":"me","lastName":"me last"}'

Enjoy