Question

I’m overriding a method that belongs to super class. Method takes no parameter. Therefore, I’m unable to pass Objects to the View using Model. Anyone has any suggestion?

@Override
protected String connectView(){
    // I'd like to include an object in Model here
    // e.g. model.addAttribute(....) 
    // but unpossible because super does not take a Model as param
    return "connect/status";
}

Answer 1

This should suit your needs, using a HandlerInterceptor, a custom annotation @Model and reflection.

Model.java

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Model {

}

RequestInterceptor.java

@Service
public class RequestInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException {
        try {
            Class<?> clazz = request.getClass();
            if (clazz.isAnnotationPresent(Controller.class)) {
                for (Field field : clazz.getDeclaredFields()) {
                    if (field.isAnnotationPresent(Model.class)) {
                        field.set(request, new ModelMap());
                        break;
                    }
                }
            }
        } catch (IllegalAccessException e) {
            // log("Cannot access model field of controller " + clazz.getSimpleName());
        }
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
        try {
            Class<?> clazz = request.getClass();
            if (clazz.isAnnotationPresent(Controller.class)) {
                for (Field field : clazz.getDeclaredFields()) {
                    if (field.isAnnotationPresent(Model.class)) {
                        ModelMap model = (ModelMap) field.get(request);
                        if (model != null) {
                            modelAndView.addAllObjects(model);
                        }
                        break;
                    }
                }
            }
        } catch (IllegalAccessException e) {
            // log("Cannot access model field of controller " + clazz.getSimpleName());
        }
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }

}

applicationContext.xml

<!-- register the interceptor -->
<mvc:interceptors>
    <bean class="your.package.to.the.RequestInterceptor" />
</mvc:interceptors>

YourController.java

@Controller
public class YourController extends ConnectController {

    @Model
    private ModelMap model;

    @Override
    protected String connectView(){
        // model is here available
        model.addAttribute("attrName", "attrValue");
        return "connect/status";
    }

}