JSF valueChangeListener Tag
This tag is used to add a value change listener to the
component associated with the enclosing tag. Value change event is fired when
the user changes the input value. This event can be fired with any component
which takes user input (select or input components). The class which is
registered with the component implements ValueChangeListener interface and
implements the method processValueChange(). We write our logic of action
in this method. One thing that we have to take care is that we have to use
onChange event of java script which submits the form when input is changed. If
we will not do this then we will have to submit the form manually. This
illustration will explain you how to go ahead.
Code Description :
<%@ page contentType="text/html" %>
<%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>
<%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
<f:view>
<html>
<body>
<h:form>
<h:selectOneMenu id="som" value="#{MyBean.som}" title="select any one in this menu"
onchange="submit()">
<f:selectItem id="si1" itemLabel="Thums Up" itemValue="11" />
<f:selectItem id="si2" itemLabel="Limca" itemValue="22" />
<f:selectItem id="si3" itemLabel="Pepsi" itemValue="33" />
<f:selectItem id="si4" itemLabel="Sprite" itemValue="44" />
<f:selectItem id="si5" itemLabel="Frooti" itemValue="55" />
<f:selectItem id="si6" itemLabel="Coca-Cola" itemValue="66" />
<f:valueChangeListener type="roseindia.MyBean" />
</h:selectOneMenu>
</h:form>
</body>
</html>
</f:view> |
MyBean.java :
package roseindia;
import java.util.*;
import javax.swing.*;
import javax.faces.event.*;
public class MyBean implements ActionListener,ValueChangeListener{
String som = "";
private Date today = new Date();
public void processAction(ActionEvent e){
JOptionPane.showMessageDialog(null,"Hi");
}
public void processValueChange(ValueChangeEvent ce){
JOptionPane.showMessageDialog(null, ce.getSource());
}
public String getSom(){
return som;
}
public void setSom(String som){
this.som = som;
}
public Date getToday(){
return today;
}
public void setToday(Date today) {
this.today = today;
}
} |
Rendered Output : This is the first page that
appears to the user.
When the user changes the current value in the menu then the value change
listener is activated and gives its output according to the method
processValueChange(). Here, in this example, a message dialog is open and
message is shown.
Html Source Code :
<html>
<body>
<form id="_id0" method="post" action="/f-tags/pages/valueChangeListener/valueChangeListener.jsf"
enctype="application/x-www-form-urlencoded">
<select id="_id0:som" name="_id0:som" size="1" onchange="submit()" title="select any one in this menu">
<option value="11">Thums Up</option>
<option value="22">Limca</option>
<option value="33">Pepsi</option>
<option value="44">Sprite</option>
<option value="55">Frooti</option>
<option value="66">Coca-Cola</option>
</select>
<input type="hidden" name="_id0" value="_id0" /></form>
</body>
</html> |
This tag contains one attribute :
type : This attribute is used to specify the
fully qualified name of the class which has implemented valueChangeListener
interface and implemented processValueChange() method.
|
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