Question

I would like to know how am I able to redirect the request inside the controller constructor if I need to do it?

For example: Inside the constructor I need to check some condition and if doesn’t met I want to redirect to some other place. At the same way the rest of the constructor will not be executed neither the “original following action”. I want the code like this.

@Controller
class SampleController{
   public SampleController(){
      if(![some condition]){
         ...redirecting code...
      }
      ...rest code...
   }

   ...rest code...
}

EDIT

If constructor is not a good option or approach then is there any option like before filter that will execute always before every action of a constructor and will redirect on the failure of some conditions?

Answer 1

You could use an interceptor:

public class CheckInterceptor implements HandlerInterceptor {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws ServletException {
        if (handler instanceof TheController) {
        // or for any controller: if (handler.getClass().isAnnotationPresent(Controller.class))
            if (!check()) {
                redirect("/check-failure.html");
                return false;
            }
        }
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
    }

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

    private void redirect(HttpServletRequest request, HttpServletResponse response, String path) throws ServletException {
        try {
            response.sendRedirect(request.getContextPath() + path);
        } catch (IOException e) {
            throw new ServletException(e);
        }
    }

    private boolean check() {
        return ...
    }

}

Then register it within the applicationContext.xml:

<mvc:interceptors>
    <bean class="your.package.CheckInterceptor" />
</mvc:interceptors>