Create own class that transforms HTTP request to object in Spring? - spring

Question

I would like to create own class that will transform HTTP request and initializes object from this HTTP request in my Spring MVC application. I can create object by defining parameters in method but I need to do mapping in my own way and do it manually.
How can I do it with my own implementation that will pass to Spring and it will use it seamlessly?
Update1
Solution that kindly provided Bohuslav Burghardt doesn't work:
HTTP Status 500 - Request processing failed; nested exception is
java.lang.IllegalStateException: An Errors/BindingResult argument is
expected to be declared immediately after the model attribute, the
#RequestBody or the #RequestPart arguments to which they apply: public
java.lang.String
cz.deriva.derivis.api.oauth2.provider.controllers.OAuthController.authorize(api.oauth2.provider.domain.AuthorizationRequest,org.springframework.ui.Model,org.springframework.validation.BindingResult,javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
Maybe I should mention that I use own validator:
public class RequestValidator {
public boolean supports(Class clazz) {
return AuthorizationRequest.class.equals(clazz);
}
public void validate(Object obj, Errors e) {
AuthorizationRequest request = (AuthorizationRequest) obj;
if ("foobar".equals(request.getClientId())) {
e.reject("clientId", "nomatch");
}
}
}
and declaration of my method in controller (please not there is needed a validation - #Valid):
#RequestMapping(value = "/authorize", method = {RequestMethod.GET, RequestMethod.POST})
public String authorize(
#Valid AuthorizationRequest authorizationRequest,
BindingResult result
) {
}
I have two configurations classes in my application.
#Configuration
#EnableAutoConfiguration
#EnableWebMvc
#PropertySource("classpath:/jdbc.properties")
public class ApplicationConfig {
}
and
#Configuration
#EnableWebMvc
public class WebappConfig extends WebMvcConfigurerAdapter {
#Override
public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
argumentResolvers.add(new AuthorizationRequestArgumentResolver());
}
}
What is wrong?
Update 2
The problem is with param BindingResult result, when I remove it it works. But I need the result to process it when some errors occur.

Answer 1

If I understand your requirements correctly, you could implement custom HandlerMethodArgumentResolver for that purpose. See example below for implementation details:
Model object
public class AuthorizationRequestHolder {
#Valid
private AuthorizationRequest authorizationRequest;
private BindingResult bindingResult;
// Constructors, accessors omitted
}
Resolver
public class AuthorizationRequestMethodArgumentResolver implements HandlerMethodArgumentResolver {
#Override
public boolean supportsParameter(MethodParameter parameter) {
return AuthorizationRequestHolder.class.isAssignableFrom(parameter.getParameterType());
}
#Override
public Object resolveArgument(MethodParameter parameter,
ModelAndViewContainer mavContainer,
NativeWebRequest webRequest,
WebDataBinderFactory binderFactory) throws Exception {
HttpServletRequest request = (HttpServletRequest) webRequest.getNativeRequest();
// Map the authorization request
AuthorizationRequest authRequest = mapFromServletRequest(request);
AuthorizationRequestHolder authRequestHolder = new AuthorizationRequestHolder(authRequest);
// Validate the request
if (parameter.hasParameterAnnotation(Valid.class)) {
WebDataBinder binder = binderFactory.createBinder(webRequest, authRequestHolder, parameter.getParameterName());
binder.validate();
authRequestHolder.setBindingResult(binder.getBindingResult());
}
return authRequestHolder;
}
}
Configuration
#Configuration
#EnableWebMvc
public class WebappConfig extends WebMvcConfigurerAdapter {
#Override
public void addArgumentResolvers(List<HandlerMethodArgumentResolver> argumentResolvers) {
argumentResolvers.add(new AuthorizationRequestMethodArgumentResolver());
}
}
Usage
#RequestMapping("/auth")
public void doSomething(#Valid AuthRequestHolder authRequestHolder) {
if (authRequestHolder.getBindingResult().hasErrors()) {
// Process errors
}
AuthorizationRequest authRequest = authRequestHolder.getAuthRequest();
// Do something with the authorization request
}
Edit: Updated answer with workaround to non-supported usage of #Valid with HandlerMethodArgumentResolver parameters.