In this example, we are going to demonstrate a simple way to implement a hidden value field in JSF. Hidden value fields, are used to submit data that are not inserted and authorised from the user. Some years ago (J2EE 1.4), a hidden value field was one of the three techniques that were used to implement web sessions.
In JSF, we can use the <h:inputHidden /> tag, in order to render an HTML hidden value field. For example, the JSF tag <h:inputHidden value="sample text" /> will render back, this HTML tag expression:
<input type="hidden" name="random value" value="some text" />. By the end of this example, you will be able to render hidden value fields through <h:inputHidden /> tag and to also access the hidden values of them, with Javascript.
1. Managed Bean
Our usual, simple Managed Bean, declared as “user”.
UserBean.java
package com.javacodegeeks.enterprise.jsf.hiddenvalue;
import java.io.Serializable;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
@ManagedBean(name="user")
@SessionScoped
public class UserBean implements Serializable{
private static final long serialVersionUID = 7134492943336358840L;
String answer = "Hi from hidden value!";
public String getAnswer() {
return answer;
}
public void setAnswer(String answer) {
this.answer = answer;
}
}
2. Our Page
Its scope is to render a hidden value through the fore-mentioned JSF tag and if a button event occurs, then it has to print the value of our hidden field; as we already said, this will be implemented with Javascript.
index.xhtml
<?xml version="1.0" encoding="UTF-8"?>
<!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>JSF Hidden Value Example</title>
<script type="text/javascript">
function printHiddenValue()
{
alert(document.getElementById('simpleform:hiddenID').value);
}
</script>
</h:head>
<h:body>
<h1>JSF 2.0 Hidden Value Example</h1>
<h:form id="simpleform">
<h:inputHidden value="#{user.answer}" id="hiddenID" />
<h:commandButton value="Click Me!" onclick="printHiddenValue()" />
</h:form>
</h:body>
</html>
3. Demo
Another very simple example, let’s try to run our application by accessing http://localhost:8080/HiddenValueJSF ; if everything goes right, after clicking the button under our page’s heading, we should get something like this:
This was an example of Hidden Value in JSF 2.0. You can also download the source code for this example: HiddenValueJSF
