4 Remarkable Notes for JSF Apps Using HTML5

In the previous post, I've already shared with you how my team consults clients by using a HTML prototype. This post is about the used technologies for reusing the provided HTML template and communicating with backend.

What is the issue when using HTML elements with Primefaces components?

Primefaces is a great extension for developing JSF web apps. However, it is really frustrating in case we have to make it work with an existing HTML template. Why?
- Primefaces has its own theme for styling.
- Primefaces changes the HTML structure.
Therefore, that would be a huge effort to use the Primefaces' components to replicate the elements of the HTML template; especially it is impossible for images drawing by "canvas" tag.

That requires us to find a better approach. Since Java EE 7 (introducing JSF 2.2 included), it supports to use HTML5 elements. The idea is that JSF components don't effect the style and HTML structure, so we can easily reuse the provided HTML template. Moreover, we're still able to use Primefaces "No-GUI" components such as "p:ajax", "p:remoteCommand'.

1. JSF Alternatives for HTML5 elements

We can choose to use JSF components, HTML5 elements, or both. Take a look the table "How Facelets Renders HTML5 Elements" of the following link for more detail.
https://docs.oracle.com/javaee/7/tutorial/jsf-facelets009.htm
For example:

<html ... xmlns:jsf="http://xmlns.jcp.org/jsf"
...
    <input type="email" jsf:id="email" name="email"
           value="#{reservationBean.email}" required="required"/>

2. Radio button or How to make a trick for events

There is no JSF component for radio elements. We have to build an alternative by our own. For example:

<div id="gender">
 <div class="control">
  <input type="radio" name="option" checked="true"
   onclick="document.getElementById('gender-hidden-input').setAttribute('value', '0'); onGenderChange();" value="0"></input>
  <label class="control__label" for="optionone">Option One</label>
 </div>
  
 <div class="control">
  <input type="radio" name="option" 
    onclick="document.getElementById('gender-hidden-input').setAttribute('value', '1'); onGenderChange();" value="1"></input>
  <label class="control__label" for="optiontwo">Option Two</label>
 </div>
  
 <h:inputText value="#{data.dataModel.gender}" styleClass="hidden" type="text" id="gender-hidden-input" />
 <p:remoteCommand name="onGenderChange" actionListener="#{logic.onGenderChange}" update="growl"></p:remoteCommand>
</div>

3. Dialog or How to custom Ajax requests

For dialogs/pop-ups, we can use a JQuery library like basicLightbox. We can use "p:remoteCommand" to call ajax  requests to backend. The following is an idea for passing a javascript function as param when executing from different places.

...
okElem.forEach(function (elem) {
 elem.onclick = function (e) {
  
  if(elem.classList.contains("mf-ui-disabled")){
   return false;
  }
  
  var ajaxRequestor = elem.getAttribute('data-ajax-requestor');
  if(ajaxRequestor){
   executeFunction(ajaxRequestor); //ajaxRequestor is a javascript function name which can make by "p:remoteCommand"
  }
  
  instance.close();
  e.preventDefault();
 };
});

...

function executeFunction(functionStr){
 var fn = window[functionStr];
 if (typeof fn === "function") fn();
}

4. Images Exporting

So far, html2Canvas has been the only one library can help us satisfy the requirements of exporting images from client side for all supported browsers including Chrome, Firefox and IE11. Almost other libraries for "html and canvas conversion" won't work with IE due to IE does not support SVG <foreignObject> tag. A fun fact here is this library even has not been released at the time we applied it for our project.

function exportProductChart(){
 
 var productHouse = document.querySelector("#overallPdfExportHouseWrapper");
 
 html2canvas(productHouse, {
   scale: 3,
      onrendered: function(canvas) {
       var productHouseImg = canvas.toDataURL("image/png");
       onClickExportPdfDialogOkBtn = function() {//override the function "onClickExportPdfDialogOkBtn" because this function can be called in another place.

     PrimeFaces.ab({
      s:"onClickExportPdfDialogOkBtn",
      f:"mainForm",
      p:"pdfExportDialog",
      u: "pdfExportDialog",
      onco:function(xhr,status,args){
       $('[id$=downloadPdf]').click();
      },
      pa:[{name: "mfDialogAction", value: "productChartExport"},
          {name: "productChoiceHouse", value: productHouseImg}]
     });
    }
    onClickExportPdfDialogOkBtn(); //p:remote command
    }
 });
}

References:
[1]. http://www.oracle.com/technetwork/articles/java/enterprise-html5-2227136.html
[2]. https://docs.oracle.com/javaee/7/tutorial/jsf-facelets009.htm
[3]. https://github.com/tsayen/dom-to-image