title: Getting value of RequestParam within an Interceptor
body: <p>I hope you can help me. I have a Spring Interceptor to authorize users based  on the URL configured in @RequestMapping of controller methods and the arguments (parameters) passed to the controller. All these request parameters are configured using the @RequestParam annotation. I need to retrieve the values passed from the @RequestParam within the Interceptor so that I can use those parameters to validate if the url has been accessed by the correct user and if the user is allowed to pass in the documentId. Please let me know if this is possible. When I do request.getParameter("documentId"), I dont get anything. I have some code as below</p>
  
  <p>(Controller Method)</p>
  
  <pre><code>@RequestMapping(value = "/viewDocument.html")
  public ModelAndView viewDocument(@RequestParam("documentId");
  </code></pre>
  
  <p>Intercept class</p>
  
  <pre><code>@Override
  public boolean preHandle(final HttpServletRequest req, final HttpServletResponse resp, final Object handler) throws IOException {
  
      if (handler instanceof HandlerMethod) {
          final HandlerMethod handlerMethod = (HandlerMethod) handler;
          final RequestMapping requstMapping = handlerMethod.getMethodAnnotation(RequestMapping.class);
  
          if (requstMapping != null) {
              final AuthorizeRequest authorizeRequestAnnotation = handlerMethod.getMethodAnnotation(AuthorizeRequest.class);
              if (authorizeRequestAnnotation != null) {
                  try {
                      checkAccess(req, requstMapping, handlerMethod);                        
                  } catch (final SecurityException e) {
                      resp.sendError(HttpServletResponse.SC_FORBIDDEN, "You are not allowed to perform this function");
                      // return false;
                  } catch (final Exception e) {
                      resp.sendError(HttpServletResponse.SC_BAD_REQUEST);
                      // return false;
                  }
              }
          }
      }
  
      return true;
  }
  
  private void checkAccess(final HttpServletRequest req, final RequestMapping requestMapping, final HandlerMethod handlerMethod) throws SecurityException {
  
      final Map&lt;String, Object&gt; arguments = Maps.newHashMap();
  
      final RequestMethod[] methods = requestMapping.method();
      final MethodParameter[] methodParameters = handlerMethod.getMethodParameters();
  
      for (final MethodParameter methodParameter : methodParameters) {
          String parameterName = null;
  
          final RequestParam requestParam = methodParameter.getParameterAnnotation(RequestParam.class);
          if (requestParam != null) {
              parameterName = requestParam.value();
              arguments.put(parameterName, req.getParameter(parameterName));
          }
      }
  
      final RuleValidator ruleValidator = rulesConfiguration.get(requestMapping.value()[0]);
      ruleValidator.validate(arguments);
  }
  </code></pre>
  
  <p>It is a GET method I am working with. Yes, If I remove the interceptor, documentId is sent. Below is my config for interceptors</p>
  
  <pre><code>&lt;mvc:interceptors&gt;
     &lt;bean class="mypackage.SecurityInterceptor" /&gt;
  &lt;/mvc:interceptors&gt;
  </code></pre>