Java Behind Obvious: Populating a JS load function with JSF values

You can find this recipe in JSF 2.0 Cookbook from Packt

As you know, when a web page is loaded, the code on the page is generally processed from the top down. JS code can interfere in this top-down order in many ways, and the onload function (specified on the body tag) is one of these possibilities. When the page is loaded, the browser will stop at the onload function and will execute the indicated script. In this recipe,you will see how to populate that script with JSF values, provided by a managed bean.

Getting ready
We have developed this recipe with NetBeans 6.8, JSF 2.0, and GlassFish v3. The JSF 2.0 classes were obtained from the NetBeans JSF 2.0 bundled library.

How to do it...
The onload function calls our JS function, named calledOnLoad. Our function will retrieve some JSF values from a managed bean. Here it is how it will do this:


<?xml version='1.0' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html">
    <h:head>
        <title>Passing parameters on HTTP GET</title>
        <script type="text/javascript" language="javascript">
            function calledOnLoad(){
                var p_1 = '<h:outputText value="#{bean.param_1}"/>';
                var p_2 = '<h:outputText value="#{bean.param_2}"/>';
                var ot = document.getElementById("formId:textId");
                ot.textContent="Parameters from bean are:"+p_1+" and " + p_2;
            }
        </script>
    </h:head>
    <h:body onload="calledOnLoad();">
        <h:form id="formId">
            <h:outputText id="textId" value=""/>
        </h:form>
    </h:body>
</html>

The managed bean is:


package bean;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;

@ManagedBean
@RequestScoped
public class Bean {

    private String param_1 = "Me";
    private String param_2 = "You";

    public String getParam_1() {
        return param_1;
    }

    public void setParam_1(String param_1) {
        this.param_1 = param_1;
    }

    public String getParam_2() {
        return param_2;
    }

    public void setParam_2(String param_2) {
        this.param_2 = param_2;
    }
}