You’ve already examined the events that could be fired from both of Application and UIViewRoot. But those aren’t only the events that might be handled. The UIComponent – UIComponent is the base class for all user interface components in JavaServer Faces. The set of UIComponent instances associated with a particular request and response are organized into a component tree under a UIViewRoot that represents the entire content of the request or response – is also have a set of predefined system events could be listened.
The following events are fired by the UIComponent:
- PostAddToViewEvent: After a component has been added to the view root.
- PreRemoveFromViewEvent: Before a component is about to be removed.
- PostRestoreStateEvent: After the state of a component has been restored.
- PreValidateEvent: Before a component is validated.
- PostValidateEvent: After a component is validated.
- PreRenderComponentEvent: Before the component is about to be rendered.
At this tutorial, you are going to look at all mentioned events.
1. Managed Bean
IndexBean.java
package net.javabeat.jsf;
import java.util.List;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import javax.faces.component.UIComponent;
import javax.faces.component.UIInput;
import javax.faces.context.FacesContext;
import javax.faces.event.PostAddToViewEvent;
import javax.faces.event.PostRestoreStateEvent;
import javax.faces.event.PostValidateEvent;
import javax.faces.event.PreRemoveFromViewEvent;
import javax.faces.event.PreRenderComponentEvent;
import javax.faces.event.PreValidateEvent;
@ManagedBean
@ViewScoped
public class IndexBean {
private UIComponentListener listener = new UIComponentListener();
private UIInput messageInput;
public IndexBean(){
// For PreRemove
FacesContext.getCurrentInstance().getApplication().
subscribeToEvent(PreRemoveFromViewEvent.class, listener);
// For PostRestore
FacesContext.getCurrentInstance().getApplication().
subscribeToEvent(PostRestoreStateEvent.class, listener);
}
private String message = "JavaBeat Message";
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public UIComponentListener getListener() {
return listener;
}
public void setListener(UIComponentListener listener) {
this.listener = listener;
}
public UIInput getMessageInput() {
return messageInput;
}
public void setMessageInput(UIInput messageInput) {
this.messageInput = messageInput;
}
public void postAddToViewHandler(PostAddToViewEvent e){
System.out.println("Event :: "+e.toString()+" :: Being Processed ::");
}
public void preRenderComponent(PreRenderComponentEvent e){
System.out.println("Event :: "+e.toString()+" :: Being Processed ::");
}
public void preValidate(PreValidateEvent e){
System.out.println("Event :: "+e.toString()+" :: Being Processed ::");
}
public void postValidate(PostValidateEvent e){
System.out.println("Event :: "+e.toString()+" :: Being Processed ::");
}
public String delete(){
List<UIComponent> components =
FacesContext.getCurrentInstance().getViewRoot().getChildren();
for(UIComponent component : components){
if(component.getId().equals(messageInput.getId())){
FacesContext.getCurrentInstance().getViewRoot().getChildren().remove(component);
}
}
return "";
}
}
2. The View
index.xhtml
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<f:view>
<h:form prependId="false">
<h1>JavaBeat JSF 2.2 Examples</h1>
<h2>JSF2 System Events - UIComponent Events Example</h2>
<br/>
<h:panelGrid columns="3">
<h:outputText value="Enter Your Message:">
<f:event listener="#{indexBean.preRenderComponent}" type="preRenderComponent"></f:event>
</h:outputText>
<h:inputText value="#{indexBean.message}"
binding="#{indexBean.messageInput}">
<f:event listener="#{indexBean.postAddToViewHandler}" type="postAddToView"></f:event>
<f:event listener="#{indexBean.preValidate}" type="preValidate"></f:event>
<f:event listener="#{indexBean.postValidate}" type="postValidate"></f:event>
</h:inputText>
<h:commandButton value="Fire Remove From View Event" action="#{indexBean.delete}"></h:commandButton>
</h:panelGrid>
</h:form>
</f:view>
</html>
3. SystemEventListener
UIComponentListener
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package net.javabeat.jsf;
import javax.faces.component.UIComponent;
import javax.faces.event.AbortProcessingException;
import javax.faces.event.SystemEvent;
import javax.faces.event.SystemEventListener;
public class UIComponentListener implements SystemEventListener {
@Override
public void processEvent(SystemEvent event) throws AbortProcessingException {
System.out.println("Event :: "+event.toString()+" :: Being Handled");
}
@Override
public boolean isListenerForSource(Object source) {
if(source instanceof UIComponent){
return true;
}
return false;
}
}
4. Faces Configuration File
faces-config.xml
<?xml version="1.0" encoding="UTF-8"?> <faces-config xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-facesconfig_2_2.xsd" version="2.2"> <application> <resource-bundle> <base-name>net.javabeat.jsf.application</base-name> <var>msg</var> </resource-bundle> </application> </faces-config>
5. The Deployment Descriptor
web.xml
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5" metadata-complete="true"> <context-param> <description>State saving method: 'client' or 'server' (=default). See JSF Specification 2.5.2 </description> <param-name>javax.faces.STATE_SAVING_METHOD</param-name> <param-value>server</param-value> </context-param> <context-param> <param-name>javax.faces.application.CONFIG_FILES</param-name> <param-value>/WEB-INF/faces-config.xml</param-value> </context-param> <servlet> <servlet-name>Faces Servlet</servlet-name> <servlet-class>javax.faces.webapp.FacesServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>Faces Servlet</servlet-name> <url-pattern>/faces/*</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>Faces Servlet</servlet-name> <url-pattern>*.xhtml</url-pattern> </servlet-mapping> <listener> <listener-class>com.sun.faces.config.ConfigureListener</listener-class> </listener> </web-app>
6. JSF SystemEventListener – UIComponent Events Demo
The below snapshot shows you the events propagated by the different type of UIComponent and the different ways that used for handle the events.
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