CODEWITHSUNDEEP
jsfcdi
Spasitel
Spasitel

Reputation: 169

Setting bean's attribute

I'm building a simple e-shop with JSF. There is a page with a list of all the products (product-list.xhtml) and then a detail page for each product (product.xhtml). product-list.xhtml:

<?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://xmlns.jcp.org/jsf/html"
      xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
      xmlns:f="http://xmlns.jcp.org/jsf/core">
<h:head>

</h:head>
<h:body>
    <f:view>
        <h:outputText value="Number of items in the cart: #{shoppingCart.numberOfSelectedProducts}"/>
        <h:link value="Cart" outcome="cart.xhtml"/>

        <h:dataTable value="#{productController.products}" var="p">
            <h:column>
                #{p.name}
                <h:commandLink action="product.xhtml" value="Detail">
                    <f:actionListener target="#{product.id}" value="#{p.id}"/>
                </h:commandLink>
            </h:column>

            <h:column>

            </h:column>
        </h:dataTable>
    </f:view>
</h:body>

</html>

then the product.xhtml looks following:

<?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://xmlns.jcp.org/jsf/html"
      xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
      xmlns:f="http://xmlns.jcp.org/jsf/core">
<head></head>
<!--f:metadata>
    <f:event type="preRenderView" listener="#{shoppingCart.loadSelectedProduct(param.id)}"/>
</f:metadata -->
<body>
    <f:view>
        <h:graphicImage value="resources/images/img.jpg"/>
        <h:outputLabel value="The value of shoppingCart.selectedProduct is: #{shoppingCart.selectedProduct.id}"/>
    </f:view>
</body>
</html>

When I run the App in the debugger, the value set correctly to the selectedProduct attribute, but then it's not accessible in the page - the output of product.xhtml looks following (if the chosen product has ID 4):

The value of shoppingCart.selectedProduct is:

Products on the main page are loaded from RequestScoped bean's (productController) property. The ShoppingCart is then a SessionScoped bean with injected productController instance.

package main.java;

import javax.annotation.PostConstruct;
import javax.enterprise.context.SessionScoped;
import javax.inject.Named;
import java.io.Serializable;
import java.util.List;

@Named
@SessionScoped
public class ShoppingCart implements Serializable {

    private List<Product> selectedProducts;
    private int numberOfSelectedProducts;
    private Product selectedProduct;

    public Product getSelectedProduct() {
        return selectedProduct;
    }

    public void setSelectedProduct(Product selectedProduct) {
        this.selectedProduct = selectedProduct;
    }

    public List<Product> getSelectedProducts() {
        return selectedProducts;
    }

    public void setSelectedProducts(List<Product> selectedProducts) {
        this.selectedProducts = selectedProducts;
    }

    public int getNumberOfSelectedProducts() {
        return numberOfSelectedProducts;
    }

    public void setNumberOfSelectedProducts(int numberOfSelectedProducts) {
        this.numberOfSelectedProducts = numberOfSelectedProducts;
    }
}

import javax.annotation.PostConstruct;
import javax.faces.view.ViewScoped;
import javax.inject.Inject;
import javax.inject.Named;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

@ViewScoped
@Named
public class ProductController implements Serializable {

    private List<Product> products;
    @Inject
    private ShoppingCart shoppingCart;

    public void setProducts(List<Product> products) {
        this.products = products;
    }

    public ShoppingCart getShoppingCart() {
        return shoppingCart;
    }

    public void setShoppingCart(ShoppingCart shoppingCart) {
        this.shoppingCart = shoppingCart;
    }

    public List<Product> getProducts() {
        return products;
    }

    //v teto metode se pote budou nacitat produkty z DB
    @PostConstruct
    public void loadItems(){
        products = new ArrayList<>();
        products.add(new Product(1, "Nazev1", 11, "Popis1"));
        products.add(new Product(2, "Nazev2", 22, "Popis2"));
        products.add(new Product(3, "Nazev3", 33, "Popis3"));
        products.add(new Product(4, "Nazev4", 44, "Popis4"));
        products.add(new Product(5, "Nazev5", 55, "Popis5"));
        products.add(new Product(6, "Nazev6", 66, "Popis6"));
        products.add(new Product(7, "Nazev7", 77, "Popis7"));
    }

    public Product findById(final int id) {
        List<Product> product = products.stream().filter(p -> p.getId() == id).limit(1).collect(Collectors.toList());
        return product.get(0);
    }
}

package main.java;

import javax.annotation.PostConstruct;
import javax.faces.view.ViewScoped;
import javax.inject.Named;
import java.io.Serializable;

@Named
@ViewScoped
public class Product implements Serializable {
    private int id;
    private String name;
    private double price;
    private String description;

    public Product(int id, String name, double price, String description) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.description = description;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @PostConstruct
    public void init(){
        System.out.println("Product created");
    }
}

Upvotes: 0

Views: 78

Answers (1)

Selaron
Selaron

Reputation: 6184

If you add a @PostConstruct method to your @SessionScoped bean like this:

@PostConstruct
public void init() {
    System.out.println("ShoppingCart.init()");
}

You will notice that your bean is instantiated several times per request - at least one time for each #{shoppengCart...} expression. This is because using the deprecated annotation @javax.faces.bean.SessionScoped within CDI environment behaves like @NoneScoped.

You should instead use javax.enterprise.context.SessionScoped for your shopping cart.

For display of a selected product I would suggest to add a @ViewScoped bean (javax.faces.view.ViewScoped, not javax.faces.bean.ViewScoped) or even @RequestScope if you don't do AJAX stuff. (javax.enterprise.context.RequestScoped, not javax.faces.bean.RequestScoped).

Which IDE do you use - didn't it notify you that the sope used by you is deprecated?

For further reading see: How to choose the right bean scope?

In addition to the scope problem, you should probably use f:viewParam instead of f:event to inject the URL query parameter into the bean:

Instead of:

<f:metadata>
    <f:event type="preRenderView" listener="#{shoppingCart.loadSelectedProduct(param.id)}"/>
</f:metadata>

do this:

<f:metadata>
     <f:viewParam name="id" value="#{productDisplayBean.selectedProductId}"/>
</f:metadata>

Upvotes: 1

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