JSF 2 Value change listener
In JSF when user interacts with GUI components like h:inputText or h:selectOneMenu, the JSF triggers a change events .
This can be implemented in two ways.
1. Method binding- Create a method in managed bean and call this via valueChangeListener attributes
2. Using ValueChangeListener interface- Create a separate class which implements ValueChangeListener and implement processValueChange method.
Example using Method binding
1. Create a managed bean
2. Create a xhtml page
3. Run it
http://localhost:8080/vinod-jsf/changeListener.xhtml
Example using ValueChangeListener interface
1. Create a change listener class which implements ValueChangeListener
2. Create a xhtml page
3. Run it
Done!! Download example
https://github.com/kkvinodkumaran/myrepository
In JSF when user interacts with GUI components like h:inputText or h:selectOneMenu, the JSF triggers a change events .
This can be implemented in two ways.
1. Method binding- Create a method in managed bean and call this via valueChangeListener attributes
2. Using ValueChangeListener interface- Create a separate class which implements ValueChangeListener and implement processValueChange method.
Example using Method binding
1. Create a managed bean
package com.vinod.jsf;
import java.util.ArrayList;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import javax.faces.event.ValueChangeEvent;
/**
* @author vinodkariyathungalkumaran
*
*/
@RequestScoped
@ManagedBean
public class ChangeListenerBean {
public ChangeListenerBean() {
}
private String country;
private String updatedCountry;
public String getUpdatedCountry() {
return updatedCountry;
}
public void setUpdatedCountry(String updatedCountry) {
this.updatedCountry = updatedCountry;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public ArrayList getCountries() {
ArrayList countries = new ArrayList();
countries.add("India");
countries.add("Austria");
countries.add("USA");
return countries;
}
public void changeListernMethod(ValueChangeEvent e) {
setUpdatedCountry("You selected " + e.getNewValue().toString());
}
}
import java.util.ArrayList;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import javax.faces.event.ValueChangeEvent;
/**
* @author vinodkariyathungalkumaran
*
*/
@RequestScoped
@ManagedBean
public class ChangeListenerBean {
public ChangeListenerBean() {
}
private String country;
private String updatedCountry;
public String getUpdatedCountry() {
return updatedCountry;
}
public void setUpdatedCountry(String updatedCountry) {
this.updatedCountry = updatedCountry;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public ArrayList getCountries() {
ArrayList countries = new ArrayList();
countries.add("India");
countries.add("Austria");
countries.add("USA");
return countries;
}
public void changeListernMethod(ValueChangeEvent e) {
setUpdatedCountry("You selected " + e.getNewValue().toString());
}
}
2. Create a xhtml page
<?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"
xmlns:f="http://java.sun.com/jsf/core">
<head>
<title>My JSF Examples</title>
</head>
<body>
<h2>valueChangeListener Examples (Method Binding)</h2>
<h:form>
<hr />
<h:panelGrid columns="2">
<h:selectOneMenu value="#{changeListenerBean.country}"
onchange="submit()"
valueChangeListener="#{changeListenerBean.changeListernMethod}">
<f:selectItems value="#{changeListenerBean.countries}" />
</h:selectOneMenu>
<h:outputText id="country"
value="#{changeListenerBean.updatedCountry}" />
</h:panelGrid>
</h:form>
</body>
</html>
<!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"
xmlns:f="http://java.sun.com/jsf/core">
<head>
<title>My JSF Examples</title>
</head>
<body>
<h2>valueChangeListener Examples (Method Binding)</h2>
<h:form>
<hr />
<h:panelGrid columns="2">
<h:selectOneMenu value="#{changeListenerBean.country}"
onchange="submit()"
valueChangeListener="#{changeListenerBean.changeListernMethod}">
<f:selectItems value="#{changeListenerBean.countries}" />
</h:selectOneMenu>
<h:outputText id="country"
value="#{changeListenerBean.updatedCountry}" />
</h:panelGrid>
</h:form>
</body>
</html>
3. Run it
http://localhost:8080/vinod-jsf/changeListener.xhtml
Example using ValueChangeListener interface
1. Create a change listener class which implements ValueChangeListener
package com.vinod.jsf;
import javax.faces.context.FacesContext;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.ValueChangeEvent;
import javax.faces.event.ValueChangeListener;
public class MyChangeListener implements ValueChangeListener {
@Override
public void processValueChange(ValueChangeEvent event) throws AbortProcessingException {
ChangeListenerBean changeListenerBean = (ChangeListenerBean) FacesContext.getCurrentInstance().
getExternalContext().getRequestMap().get("changeListenerBean");
System.out.println(changeListenerBean);
System.out.println("Executin change listener");
changeListenerBean.setUpdatedCountry("You Selected " +event.getNewValue());
}
}
import javax.faces.context.FacesContext;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.ValueChangeEvent;
import javax.faces.event.ValueChangeListener;
public class MyChangeListener implements ValueChangeListener {
@Override
public void processValueChange(ValueChangeEvent event) throws AbortProcessingException {
ChangeListenerBean changeListenerBean = (ChangeListenerBean) FacesContext.getCurrentInstance().
getExternalContext().getRequestMap().get("changeListenerBean");
System.out.println(changeListenerBean);
System.out.println("Executin change listener");
changeListenerBean.setUpdatedCountry("You Selected " +event.getNewValue());
}
}
2. Create a xhtml page
<?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"
xmlns:f="http://java.sun.com/jsf/core">
<head>
<title>My JSF Examples</title>
</head>
<body>
<h:form>
<h2>valueChangeListener Examples (Implements ValueChangeListener
)</h2>
<h:selectOneMenu value="#{changeListenerBean.country}"
onchange="submit()">
<f:valueChangeListener type="com.vinod.jsf.MyChangeListener" />
<f:selectItems value="#{changeListenerBean.countries}" />
</h:selectOneMenu>
<h:outputText id="country1"
value="#{changeListenerBean.updatedCountry}" />
</h:form>
</body>
</html>
<!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"
xmlns:f="http://java.sun.com/jsf/core">
<head>
<title>My JSF Examples</title>
</head>
<body>
<h:form>
<h2>valueChangeListener Examples (Implements ValueChangeListener
)</h2>
<h:selectOneMenu value="#{changeListenerBean.country}"
onchange="submit()">
<f:valueChangeListener type="com.vinod.jsf.MyChangeListener" />
<f:selectItems value="#{changeListenerBean.countries}" />
</h:selectOneMenu>
<h:outputText id="country1"
value="#{changeListenerBean.updatedCountry}" />
</h:form>
</body>
</html>
3. Run it
Done!! Download example
https://github.com/kkvinodkumaran/myrepository
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