FormWithPostValidateEvent.xhtml

<h:form>
   <f:event type="postValidate" listener="#{minMax.validate}"/>
   <h:inputText id="min" value="#{bean.min}"
      binding="#{minMax.minInput}"/> <h:message for="min"/>
   <h:inputText id="max" value="#{bean.max}"
      binding="#{minMax.maxInput}"/> <h:message for="max"/>
   <h:commandButton value="Submit"/>
</h:form>

MinMax.java

public @Model class MinMax {
   @Inject FacesContext ctx;
   private UIInput minInput, maxInput; // accessors hidden
   public void validate() {
      if (ctx.isValidationFailed()) { return; }
      if ((Integer) maxInput.getValue() < (Integer) minInput.getValue()) {
         ctx.addMessage(maxInput.getClientId(ctx),
            new FacesMessage("cannot be less than min value"));
         ctx.validationFailed();
         ctx.renderResponse();
      }
   }
}