Dynamically Adding Server-Side Components to Templates

import { PolymerElement, html } from '@polymer/polymer/polymer-element.js';

class ComponentContainer extends PolymerElement {
  static get template() {
    return html`
      <div>
        <slot></slot>
      </div>
    `;
  }

  static get is() {
    return 'component-container';
  }
}

customElements.define(ComponentContainer.is, ComponentContainer);

@Tag("component-container")
@JsModule("./com/example/component-container.js")
public class ComponentContainer extends PolymerTemplate<TemplateModel> {

    public ComponentContainer() {
        Element label = ElementFactory.createLabel("Main layout header");
        Element button = ElementFactory.createButton("Click me");

        getElement().appendChild(label, button);
    }
}