Snippet

Custom Controller Argument Resolution with HandlerMethodArgumentResolver

HandlerMethodArgumentResolver allows for injecting custom objects into controller methods by resolving them from the web request context. This is highly useful for extracting security principals or specialized session data without polluting controller logic.

snippet.java

java

@Component
public class CurrentUserResolver implements HandlerMethodArgumentResolver {
    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.hasParameterAnnotation(CurrentUser.class) && 
               parameter.getParameterType().equals(UserAccount.class);
    }
 
    @Override
    public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, 
                                  NativeWebRequest webRequest, WebDataBinderFactory binderFactory) {
        HttpServletRequest request = (HttpServletRequest) webRequest.getNativeRequest();
        return request.getAttribute("authenticated_user");
    }
}

spring

Breakdown

supportsParameter(...)

Determines if the resolver is applicable based on the parameter type and annotations.

resolveArgument(...)

Performs the actual logic to extract or construct the object to be injected into the method.

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Custom Controller Argument Resolution with HandlerMethodArgumentResolver

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