Using CDI Beans in Instantiated Components

Using Router Components

When the add-on is used, all route targets, router layouts, and exception targets become managed beans. The components appear and operate the same as before, but CDI capabilities are now available.

Example

Using the @Inject annotation on a simple route-target 

@Route
public class MyView extends childMyView
{
    @Inject
    public MyView(Greeter greeter) 
    {
        add(new Span(greeter.sayHi()));
    }
}

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Using Components Injected Into Templates

When the @id annotation is used to inject components into template classes, they become managed beans.

Example 

The Deplabel component is injected into the CodingNinjas class using the @Id annotation.

Public class CodingNinjas extends Ninjas. 
{
    @Id
    private Deplabel label;
}

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Example 

Class Deplabel

@Dependent
@Tag("dependent-label")
public class Deplabel extends Label {
    @Inject
    private Greeter greeter;

    @PostConstruct
    private void init() {
        setText(greeter.sayHi());
    }
}

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Example

CodingNinjas.html Polymer template

import { html, LitElement } from 'lit';
class CodingNinjas extends LitElement {
    get render() {
        return html`
            <div>
                <dependent-label id="label"/>
            </div>`;
    }
}
customElements.define(CodingNinjas.is, CodingNinjas);

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Using a Custom UI

It is not essential to specify a custom UI subclass for your application, but you can, if necessary, by utilizing the matching servlet option.

Vaadin instantiates the custom UI subclass as a POJO (rather than a managed bean), but dependency injection is still allowed. In your overridden UI.init() function, use BeanManager; for example, 

BeanProvider.injectFields(this) (in DeltaSpike).

Frequently Asked Questions

What is Vaadin?

Vaadin is an open-source framework for deve;oping contemporary web applications. It contains a vast component library and an easy-to-use Java API. It is also compatible with Spring.

What are CDI Beans?

CDI Beans are classes that CDI can Automatically instantiate, manage and inject to meet the requirement of the Other objects. CDI can manage and inject almost any Java Class.

What happens when CDI Beans in Instantiated Components are Injected into Template?

When Components are injected into template classes using the @id annotation, they become managed beans.

What happens while using Router Components in CDI Beans?

All route targets, router layouts, and exception targets become managed beans when an add-on is used. The components seem and function normally, but CDI capabilities are now accessible. 

Is it necessary to define Custom UI?

It is not required to define a Custom UI subclass for your application, but you can, if necessary, by using the Corresponding servlet option.

Conclusion 

In this article, we learned about CDI Beans and their Usage in Instantiated Components.

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