Using CDI Beans in Instantiated Components

When using Vaadin CDI, most objects instantiated by framework become managed beans. The framework uses the CDI BeanManager to get references to beans. This means they are fully-fledged CDI contextual instances.

The add-on looks up the CDI bean by type (component class) and @Any.

If the type is not found as a CDI bean - for example, because it is ambiguous or does not have a no-arg public constructor - instantiation falls back to the default Vaadin behavior, and the component is instantiated as a POJO. Dependency injection is performed after instantiation and injects still work, but other CDI features do not. The reason is that the instantiated component is not a contextual instance.

Using Router Components

All route targets, router layouts, and exception targets become managed beans when the add-on is used. The components look and behave the same as without the add-on, but CDI features are available.

Example: Using the @Inject annotation on a basic route target.

Java

@Route
public class MainView extends VerticalLayout {
    @Inject
    public MainView(Greeter greeter) {
        add(new Span(greeter.sayHello()));
    }
}

Using Components Injected into Polymer Templates

Components injected into Polymer template classes using the @id annotation become managed beans when the add-on is used.

Example: Using the @Id annotation to inject the DependentLabel component into TestTemplate class.

Java

public class TestTemplate
        extends PolymerTemplate<TemplateModel> {
    @Id
    private DependentLabel label;
}

Example: DependentLabel class.

Java

@Dependent
@Tag("dependent-label")
public class DependentLabel extends Label {
    @Inject
    private Greeter greeter;
    @PostConstruct
    private void init() {
        setText(greeter.sayHello());
    }
}

Example: TestTemplate.html Polymer template.

js

import {PolymerElement,html} from
        '@polymer/polymer/polymer-element.js';
class TestTemplate extends Polymer.Element {
    static get template() {
        return html`
            <div>
                <dependent-label id="label"/>
            </div>`;
    }
    static get is() { return 'test-template' }
}
customElements.define(TestTemplate.is, TestTemplate);

Using a Custom UI

It is not necessary to define a custom UI subclass for your application, but it is possible to define one using the corresponding servlet parameter, if needed.

The custom UI subclass is instantiated by Vaadin as a POJO (not as a managed bean), but it is still possible to achieve dependency injection. Use BeanManager in your overridden UI.init method, for example BeanProvider.injectFields(this) (in Deltaspike).