I'm working on a Spring application, and I saw that you can declare @RequestParam Map<String, String> to have Spring automatically convert all parameters into that Map

I made a wrapper class for it as well to add convenience functionality like automatic parsers, but I was wondering if there was a way to get Spring to automatically convert the entire Map into the wrapper

I've seen other implementations of people making a POJO for data mapping, but that's not quite what I'm going for

The code for the wrapper is as follows:

public class RequestMap {
    private final Map<String, String> innerMap;

    public RequestMap(Map<String, String> map) {
        innerMap = map;
    }

    (getter/parser methods, and accessors for inner map)
}

What I'd ideally like to be able to do is:

// Old method
@PostMapping()
public Model showPage(@RequestParam Map<String, String> requestMap) {
    RequestMap request = new RequestMap(requestMap);

    // Do stuff
}

// What I'm trying to get
@PostMapping()
public Model showPage(RequestMap request) {
    // Do stuff
}

I'm working on a Spring application, and I saw that you can declare @RequestParam Map<String, String> to have Spring automatically convert all parameters into that Map

I made a wrapper class for it as well to add convenience functionality like automatic parsers, but I was wondering if there was a way to get Spring to automatically convert the entire Map into the wrapper

I've seen other implementations of people making a POJO for data mapping, but that's not quite what I'm going for

The code for the wrapper is as follows:

public class RequestMap {
    private final Map<String, String> innerMap;

    public RequestMap(Map<String, String> map) {
        innerMap = map;
    }

    (getter/parser methods, and accessors for inner map)
}

What I'd ideally like to be able to do is:

// Old method
@PostMapping()
public Model showPage(@RequestParam Map<String, String> requestMap) {
    RequestMap request = new RequestMap(requestMap);

    // Do stuff
}

// What I'm trying to get
@PostMapping()
public Model showPage(RequestMap request) {
    // Do stuff
}

• java
• spring
• http-request-parameters

• 1 Is there a reason that you do all the mapping manually instead of letting Spring do the mapping and conversion to other types? Feels like you are working around the framework instead of embracing it. – M. Deinum Commented Mar 27 at 10:42

1 Answer 1

You can register a custom HandlerMethodArgumentResolver

See the custom argument resolver example on Baeldung's website

Eg

@Configuration
public class MyWebMvcConfigurer implements WebMvcConfigurer {
    @Override
    public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
        HandlerMethodArgumentResolver resolver = new HandlerMethodArgumentResolver() {
            @Override
            public boolean supportsParameter(MethodParameter methodParameter) {
                return RequestMap.class.equals(methodParameter.getParameterType());
            }
        
            @Override
            public Object resolveArgument(MethodParameter param, ModelAndViewContainer mvContainer, NativeWebRequest request, WebDataBinderFactory binderFactory) {
                HttpServletRequest httpRequest = request.getNativeRequest(HttpServletRequest.class);
                return new RequestMap(httpRequest.getParameterMap());
            }
        };
        argumentResolvers.add(resolver);
    }
}