Get controller parameters in interceptor

Question

I am creating a validation library and I would like to validate the request before the controller. It would be really nice that I can get the controller parameter that I want to validate in the interceptor.

At the moment I can get all the info about the controller parameters, but I can't find a way to get the instance that is inside the parameter. This is what I have at the moment:

public class ValidationInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if (handler instanceof HandlerMethod) {
            HandlerMethod method = (HandlerMethod) handler;
            for (MethodParameter param: method.getMethodParameters()) {
                // Check if the parameter has the right annotations.
                if (param.hasParameterAnnotation(RequestBody.class) && param.hasParameterAnnotation(Valid.class)) {
                    // Here I wan't to get the object that is in the parameter so I can validate it.
                }
            }
        }

        return true;
    }
}

Example controller method:

@RequestMapping(value = "register", method = RequestMethod.POST)
public Response register(@Valid @RequestBody RegisterRequest request) {
    // return response and stuff.
}

RegisterRequest:

public class RegisterRequest {
    @JsonProperty("email")
    public String email;

    @JsonProperty("name")
    public String name;

    @JsonProperty("password")
    public String password;

    @JsonProperty("password_confirmation")
    public String passwordConfirmation;
}

Is there an easy way to access the controller parameters from an interceptor?

Answer 1

Not sure if yu are still looking for an answer, but I think you can do it using getPart() or getParts() method. So in above case, you can do like

Collection<javax.servlet.http.Part> parts = request.getParts();
    Iterator<javax.servlet.http.Part> it = parts.iterator();
    while(it.hasNext()){
        javax.servlet.http.Part p = it.next();
        if(p.getSubmittedFileName() != null)
            fileName = p.getSubmittedFileName();
    }

The above is just an example where I tried to fetch the name of a file I am uploading as a MultiPartFile object. Check out in request options what value of parameter you want to get.