JSF2 - use view scope managed bean to pass value between navigation
- by Fekete Kamosh
Hi all,
I am solving how to pass values from one page to another without making use of session scope managed bean. For most managed beans I would like to have only Request scope.
I created a very, very simple calculator example which passes Result object resulting from actions on request bean (CalculatorRequestBean) from 5th phase as initializing value for new instance of request bean initialized in next phase lifecycle.
In fact - in production environment we need to pass much more complicated data object which is not as primitive as Result defined below.
What is your opinion on this solution which considers both possibilities - we stay on the same view or we navigate to the new one. But in both cases I can get to previous value stored passed using view scoped managed bean.
Calculator 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">
<h:head>
<title>Calculator</title>
</h:head>
<h:body>
<h:form>
<h:panelGrid columns="2">
<h:outputText value="Value to use:"/>
<h:inputText value="#{calculatorBeanRequest.valueToAdd}"/>
<h:outputText value="Navigate to new view:"/>
<h:selectBooleanCheckbox value="#{calculatorBeanRequest.navigateToNewView}"/>
<h:commandButton value="Add" action="#{calculatorBeanRequest.add}"/>
<h:commandButton value="Subtract" action="#{calculatorBeanRequest.subtract}"/>
<h:outputText value="Result:"/>
<h:outputText value="#{calculatorBeanRequest.result.value}"/>
<h:outputText value="DUMMY" rendered="#{resultBeanView.dummy}"/>
</h:panelGrid>
</h:form>
</h:body>
Object to be passed through lifecycle:
package cz.test.calculator;
import java.io.Serializable;
/**
* Data object passed among pages.
* Lets imagine it holds something much more complicated than primitive int
*/
public class Result implements Serializable {
private int value;
public void setValue(int value) {
this.value = value;
}
public int getValue() {
return value;
}
}
Request scoped managed bean used on view "calculator.xhtml"
package cz.test.calculator;
import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ManagedProperty;
import javax.faces.bean.RequestScoped;
@ManagedBean
@RequestScoped
public class CalculatorBeanRequest {
@ManagedProperty(value="#{resultBeanView}")
ResultBeanView resultBeanView;
private Result result;
private int valueToAdd;
/**
* Should perform navigation to
*/
private boolean navigateToNewView;
/** Creates a new instance of CalculatorBeanRequest */
public CalculatorBeanRequest() {
}
@PostConstruct
public void init() {
// Remember already saved result from view scoped bean
result = resultBeanView.getResult();
}
// Dependency injections
public void setResultBeanView(ResultBeanView resultBeanView) {
this.resultBeanView = resultBeanView;
}
public ResultBeanView getResultBeanView() {
return resultBeanView;
}
// Getters, setter
public void setValueToAdd(int valueToAdd) {
this.valueToAdd = valueToAdd;
}
public int getValueToAdd() {
return valueToAdd;
}
public boolean isNavigateToNewView() {
return navigateToNewView;
}
public void setNavigateToNewView(boolean navigateToNewView) {
this.navigateToNewView = navigateToNewView;
}
public Result getResult() {
return result;
}
// Actions
public String add() {
result.setValue(result.getValue() + valueToAdd);
return isNavigateToNewView() ? "calculator" : null;
}
public String subtract() {
result.setValue(result.getValue() - valueToAdd);
return isNavigateToNewView() ? "calculator" : null;
}
}
and finally view scoped managed bean to pass Result variable to new page:
package cz.test.calculator;
import java.io.Serializable;
import javax.annotation.PostConstruct;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import javax.faces.context.FacesContext;
@ManagedBean
@ViewScoped
public class ResultBeanView implements Serializable {
private Result result = new Result();
/** Creates a new instance of ResultBeanView */
public ResultBeanView() {
}
@PostConstruct
public void init() {
// Try to find request bean ManagedBeanRequest and reset result value
CalculatorBeanRequest calculatorBeanRequest = (CalculatorBeanRequest)FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("calculatorBeanRequest");
if(calculatorBeanRequest != null) {
setResult(calculatorBeanRequest.getResult());
}
}
/** No need to have public modifier as not used on view
* but only in managed bean within the same package
*/
void setResult(Result result) {
this.result = result;
}
/** No need to have public modifier as not used on view
* but only in managed bean within the same package
*/
Result getResult() {
return result;
}
/**
* To be called on page to instantiate ResultBeanView in Render view phase
*/
public boolean isDummy() {
return false;
}
}
