Author
James Chu, Potix Corporation

Date
January 31, 2020

Version
ZK 9.0.0

Overview

In the recently released ZK9, we provide a new way to integrate applications with ZK and front-end frameworks - Embedded ZK. For instance, we can integrate Vue. VueJS is a progressive framework for building user interfaces. With the Embedded ZK feature in ZK9, we could easily combine VueJS and ZK together. In the following demo project, we will use ZK client-side binding, Embedded ZK, Bootstrap and VueJS to demonstrate how this can be done.

Prepare data and ZK settings (Java)

As we can see, this demo is a forum project. This demo contains several parts on the server-side:

1. Data object

2. View Models

3. Define ZK Binder in ZUL files

4. Enable Embedded ZK

Data Object

There are two main entity classes - User and Article.

org.zkoss.demo.forum.entity.User

public class User {
  private int uid;
  private String account;
  private String password;
  private String name;
  //... getters/setters are omitted
}

org.zkoss.demo.forum.entity.Article

public class Article {
  private int uid;
  private User user;
  private String subject;
  private String thumbnail;
  private String content;
  private Date lastEditedTime;
  //... getters/setters are omitted
}

When using ZK client-binding, the two data objects would be converted into JSON object. Therefore we could inject the data into Vue components later.

ZK View Models and ZUL Files

In the view model, we need to prepare the binder and define the commands that would be called on the client-side.

Client-side Binding in View Model (Server to Client)

org.zkoss.demo.forum.viewmodel.ArticleListVM

@NotifyCommand(value = "toC_Articles", onChange = "_vm_.articles")
@ToClientCommand({ "toC_Articles"})
@ToServerCommand({ "loadArticles", "loadArticleById"})
public class ArticleListVM {
  @Command
  @NotifyChange("articles")
  public void loadArticles() {
    articles = articleService.getRecentArticles();
  }
  //omitted
}

Line 1 & 2: When the property "articles" is changed, ZK would fire a client command "toC_Articles" to the client-side.

Line 3: Allow client-side binders to call specific commands.

Define ZK Binder in ZUL files

src/main/resources/web/zul/articles.zul

<div id="articles-binder" viewModel="@id('vm') @init('org.zkoss.demo.forum.viewmodel.ArticleListVM')" />

The id "articles-binder" is defined for the ZK Client-binding Javascript API.

Enable Embedded ZK

We use the library property to enable Embedded ZK.

zk.xml

<library-property>
	<name>org.zkoss.web.servlet.http.embedded.enabled</name>
	<value>true</value>
</library-property>

Integrate with VueJS (Javascript)

Before integrating with VueJS, we need to load embedded ZK in the HTML file.

Sets Embedded ZK

src/main/resources/static/index.html

<body>
  <!-- omitted -->
  <div id="embeddedZK"></div>
  <!-- omitted -->
</body>

Use a div to embed ZK binder DOM ($articles-binder).

src/main/resources/static/js/app.js

zEmbedded.load('embeddedZK', '/articles');
window.addEventListener('load', function(){
  zk.afterMount(function () {
    // Initialize Vue Components after ZK is mounted
  });
}

Line 1: '/articles' would redirect to the specific URL path (articles.zul) Notice that all the data transfer from the ZK server to the client should wait for ZK being mounted.

Use ZK Client-side binding in Vue (Client to Server)

After loading the embedded ZK, we used client-side binding in Vue instances.

1. To trigger commands in ZK Server, we used Binder.command(command, args, ...).

2. To get the result from the ZK server, we used Binder.after(command, callback) to register the callback function.

src/main/resources/static/js/app.js

// inside zk.afterMount
var articlesBinder = zkbind.$('$articles-binder');
new Vue({
  el: '#articles',
  data: {
    articles: []
  },
  beforeMount() {
    this.loadArticles();
  },
  methods: {
    loadArticles () {
      var self = this,
        changeArticles = function (data) {
          self.articles = data;
          articlesBinder.unAfter('toC_Articles', changeArticles);
        };
      articlesBinder.after('toC_Articles', changeArticles);
      articlesBinder.command('loadArticles');
    }
    //omitted
  }
});

Line 2: Looking for the ZK binder.

Line 4: Vue dom selector.

Line 9: Trigger the loading method before Vue is mounted.

Line 14: Prepare a callback function to update articles.

Line 16: Unregister the callback.

Line 18: Register a callback function, it would be triggered when receiving the client command - "toC_Articles".

Line 19: Use ZK Client-binding API to trigger a command on the server-side.

Since the data "articles" is a list, we use List Rendering in VueJs.

src/main/resources/static/index.html

<div id="articles" class="...">
  <!-- omitted -->
  <article-block v-for="article in articles"
    v-bind:key="article.uid" v-bind:subject="article.subject" v-bind:thumbnail="article.thumbnail"
    v-bind:username="article.user.name"  v-bind:time="article.publishedTime"
    v-on:view="view(article.uid)">
  </article-block>
  <!-- omitted -->
</div>

Line 3: "article-block" is a Vue component, and we use the List rendering

Line 5: the property "article.user.name" is fully referred to the data from Java Bean

Summary

The core value of ZK is to allow you to build a Web UI quickly with pure Java. However, in some cases, you may need to integrate a specific 3rd-party front-end framework with ZK. With embedded ZK, using such front-end frameworks with ZK becomes easier. I hope this article will give you some hints on how you can get this done. Please feel free to leave comments below or create a discussion on ZK forum.

Download

You can download all of the source code for this demo in Github

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