Save State & Managed Beans - Scopes

Managed Beans - Scopes

Existen diferentes niveles o alcances de ManagedBeans,

Request Scope

Se instancia y se pobla el Bean en cada request, con información de Request.

package com.roshka.tutorial.jsf;

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

@ManagedBean(name = "requestBean")
@RequestScoped
public class RequestManagedBean {
 private static org.apache.log4j.Logger logger = org.apache.log4j.Logger
   .getLogger(RequestManagedBean.class);

 Form form;

 public RequestManagedBean() {
  logger.info("RequestManagedBean.RequestManagedBean: constructor");
 }

 @PostConstruct
 public void postConstruct() {
  logger.info("RequestManagedBean.postConstruct: ");
  form = new Form();
  form.setName("Name...");
 }

 public String save() {
  logger.info("RequestManagedBean.save: ");
  logger.info("RequestManagedBean.save: " + form.getName());
  return null;
 }

 public String save(Form form) {
  logger.info("RequestManagedBean.save: ");
  this.form = form;
  return null;
 }

 public Form getForm() {
  return form;
 }

 public void setForm(Form form) {
  this.form = form;
 }

}

View Scope (Desde JSF 2)

En el primer GET al VIEW se instancia el BEAN, se guarda la instancia en la Sesión del usuario pero solo puede ser accedida desde el mismo VIEW.

package com.roshka.tutorial.jsf;

import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

@ManagedBean(name = "viewBean")
@ViewScoped
public class ViewManagedBean {
 private static org.apache.log4j.Logger logger = org.apache.log4j.Logger
   .getLogger(ViewManagedBean.class);
 Form form;

 public ViewManagedBean() {
  logger.info("ViewManagedBean.ViewManagedBean: constructor");
 }

 @PostConstruct
 public void postConstruct() {
  logger.info("ViewManagedBean.postConstruct: ");
  form = new Form();
  form.setName("Name...");
 }

 public String save() {
  logger.info("ViewManagedBean.save: ");
  logger.info("ViewManagedBean.save: " + form.getName());
  return null;
 }
 public String save(Form form) {
  logger.info("ViewManagedBean.save: ");
  this.form = form;
  return null;
 }

 public Form getForm() {
  return form;
 }

 public void setForm(Form form) {
  this.form = form;
 }
}

Session Scope

Se crea una instancia por Sesión y para todas las Views se comparte la misma instancia

package com.roshka.tutorial.jsf;

import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;

@ManagedBean(name = "sessionBean")
@SessionScoped
public class SessionManagedBean {
 private static org.apache.log4j.Logger logger = org.apache.log4j.Logger
   .getLogger(SessionManagedBean.class);

 Form form;

 public SessionManagedBean() {
  logger.info("SessionManagedBean.SessionManagedBean: constructor ");
 }

 @PostConstruct
 public void postConstruct() {
  logger.info("SessionManagedBean.SessionManagedBean: ");
  form = new Form();
  form.setName("Name...");
 }

 public String save() {
  logger.info("SessionManagedBean.save: ");
  logger.info("SessionManagedBean.save: " + form.getName());
  return null;
 }
 public String save(Form form) {
  logger.info("SessionManagedBean.save: ");
  this.form = form;
  return null;
 }
 public Form getForm() {
  return form;
 }

 public void setForm(Form form) {
  this.form = form;
 }
}

ApplicationScope

Se crea una instancia para la aplicación, Se comparte entre todos los Views de Todas las Sesiones. Ojo! No utilizar para guardar información sensible de un usuario.

package com.roshka.tutorial.jsf;

import javax.annotation.PostConstruct;
import javax.faces.bean.ApplicationScoped;
import javax.faces.bean.ManagedBean;

@ManagedBean(name = "applicationBean")
@ApplicationScoped
public class ApplicationManagedBean {
 private static org.apache.log4j.Logger logger = org.apache.log4j.Logger
   .getLogger(ApplicationManagedBean.class);
 Form form;

 public ApplicationManagedBean() {
  logger.info("ApplicationManagedBean.ApplicationManagedBean: constructor");
 }

 @PostConstruct
 public void postConstruct() {
  logger.info("ApplicationManagedBean.postConstruct: ");
  form = new Form();
  form.setName("Name...");
 }

 public String save() {
  logger.info("ApplicationManagedBean.save: ");
  logger.info("ApplicationManagedBean.save: " + form.getName());
  return null;
 }
 public String save(Form form) {
  logger.info("ApplicationManagedBean.save: ");
  this.form = form;
  return null;
 }

 

 public Form getForm() {
  return form;
 }

 public void setForm(Form form) {
  this.form = form;
 }
}

Se puede ver utilizando los ejemplos

request-scope/example.xhtml
view-scope/example.xhtml
session-scope/example.xhtml
application-scope/example.xhtml
all-scopes/example.xhtml

 Save Views State

Para guardar la información del Estado de del View (ViewSate) se pueden seleccionar entre guardar en el Servidor o Guardar en el Servidor; Guardar en el Servidor implica consumo de memoria y Guardar en el Cliente implica mayor tráfico de Red.

Server Side

<context-param>
  <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
  <param-value>server</param-value>
 </context-param>

Client Side

<context-param><param-name>javax.faces.STATE_SAVING_METHOD</param-name>
  <param-value>client</param-value>
 </context-param>

Enlace Interesante

Para conocer más acerca de Save State, se puede leer la siguiente discusión stackoverflow.com
Descargar ejemplos desde Aquí