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JSF2 - use a bean-controlled viewport to pass values ​​between navigation

I decide how to transfer values ​​from one page to another without using the bean management session area. For most managed beans, I would like to have only a request scope.

I created a very simple example of a calculator that passes the Result object obtained as a result of actions on a bean request (CalculatorRequestBean) from the 5th phase as the initialization value for a new instance of the bean request, initialized in the next phase life cycle.

In fact, in a production environment, we need to transfer a much more complex data object, which is not as primitive as the result indicated below.

What is your opinion on this decision, which considers both possibilities - we remain in the same view or move on to a new one. But in both cases, I can go back to the previous value stored by the bean managed scope.

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:commandButton value="Calculator2" action="calculator2"/>

            <h:outputText value="DUMMY" rendered="#{resultBeanView.dummy}"/>
        </h:panelGrid>
    </h:form>
</h:body>

Calculator2 page with operations to multiply and divide:

<?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 2</title>
    </h:head>
    <h:body>
        <h:form>
            <h:panelGrid columns="2">
                <h:outputText value="Value to use:"/>
                <h:inputText value="#{calculatorBeanRequest2.valueToAdd}"/>

                <h:outputText value="Navigate to new view:"/>
                <h:selectBooleanCheckbox value="#{calculatorBeanRequest2.navigateToNewView}"/>

                <h:commandButton value="Multiply" action="#{calculatorBeanRequest2.multiply}"/>
                <h:commandButton value="Divide" action="#{calculatorBeanRequest2.divide}"/>

                <h:outputText value="Result:"/>
                <h:outputText value="#{calculatorBeanRequest2.result.value}"/>

                <h:commandButton value="Calculator" action="calculator"/>

                <h:outputText value="DUMMY" rendered="#{resultBeanView.dummy}"/>
            </h:panelGrid>
        </h:form>
    </h:body>
</html>

The object that must go through the life cycle:

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 a managed managed bean used in the "calculator.xhtml" view with add and subtract actions

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;
    }
}

Request the managed bean control used in the "calculator2.xhtml" view with actions, split and propagate:

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 CalculatorBeanRequest2 {

    @ManagedProperty(value="#{resultBeanView}")
    ResultBeanView resultBeanView;

    private Result result;

    private int valueToUse;

    /**
     *  Should perform navigation to
     */
    private boolean navigateToNewView;

    /** Creates a new instance of CalculatorBeanRequest2 */
    public CalculatorBeanRequest2() {
    }


    @PostConstruct
    public void init() {
        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.valueToUse = valueToAdd;
    }

    public int getValueToAdd() {
        return valueToUse;
    }

    public boolean isNavigateToNewView() {
        return navigateToNewView;
    }

    public void setNavigateToNewView(boolean navigateToNewView) {
        this.navigateToNewView = navigateToNewView;
    }

    public Result getResult() {
        return result;
    }

    // Actions
    public String multiply() {
        result.setValue(result.getValue() * valueToUse);
        return isNavigateToNewView() ? "calculator2" : null;
    }

    public String divide() {
        result.setValue(result.getValue() / valueToUse);
        return isNavigateToNewView() ? "calculator2" : null;
    }    
}

and finally, review the managed bean control to pass the result variable to a 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());
        }
        CalculatorBeanRequest2 calculatorBeanRequest2 =  (CalculatorBeanRequest2)FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("calculatorBeanRequest2");
        if(calculatorBeanRequest2 != null) {
            setResult(calculatorBeanRequest2.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;
    }

}
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, bean, .

(). JSF , .

(, calculator.xthml result_overview.xhtml), conversation scope Java EE 6. JSF 2.0 libs, Tomcat, , CDI Java EE AS, ​​ Glassfish V3 Jboss AS 6, .

, , beans @ManagedBean @Named , CDI beans, JSF beans. , .

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Source: https://habr.com/ru/post/1783099/

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