Category Archives: JavaScript

Developing Front-End Microservices With Polymer Web Components And Test-Driven Development (Part 5/5): Using Microservices

In the previous article we built two Web Components (tc-book-form and tc-books), learned how to change their style through properties, how to control them through exposed functions as well as how to connect them using custom events. We developed most of the code using Test-Driven Development approach. Both front-end Web Components and back-end server are packed into a single microservice and stored as a Docker container. We did not do the last part (Docker build, push and run) together and we’ll correct that by exploring, among other things, containers definition, building and running in this article.

With all this in place, we are ready to import components we did in previous articles into a separate Web Application.

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Developing Front-End Microservices With Polymer Web Components And Test-Driven Development (Part 4/5): Styling And Communication

In the previous article we developed our second Polymer Web Component. With two of them functionally finished, we’ll apply styles and create a way for users of our components to have partial control of the look and feel. Once that is done, we’ll improve our Demo page and create proper communication between our components.

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Developing Front-End Microservices With Polymer Web Components And Test-Driven Development (Part 3/5): The Second Component

In the previous article we finished one Polymer Web Component. It contained a form that could be used to add, update and remove books by sending HTTP requests to the back-end server. We also explored few different ways to interact with the component from outside by calling its functions.

In this article we’ll create the second component that will be used to list all the books and send custom events to open an existing or a new book. Those events will not be sent directly to the component we built earlier but to the document the component will reside on. We’ll get to that part in time…

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Developing Front-End Microservices With Polymer Web Components And Test-Driven Development (Part 2/5): Polishing The First Component

book-form-scIn the previous article we created our first Polymer Web Component using Test-Driven Development approach. While all the specifications we wrote were implemented, there are still few things we should do to polish this component. The tc-book-form currently has the form with all the input fields required by the back-end. It also has buttons to add or update and delete a book. Those buttons are calling iron-ajax Polymer element that sends requests to the back-end. Both front-end (in form of Web Component) and back-end are developed as a single microservice.

The next task in front of us is to polish the component. Later on in this series we’ll create another component that will list all books. We’ll also develop the code that will enable us to establish communication between those two components. Once we’re done with both, we’ll explore ways to integrate the microservices we developed into a separate Web Application.

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Developing Front-End Microservices With Polymer Web Components And Test-Driven Development (Part 1/5): The First Component

In this article series we’ll go through Web Components development in context of microservices. We’ll use Polymer as the library that will help us out. The objective is to create a microservice that will handle full functionality. The service will contain not only back-end API (as is the case with most microservices) but also front-end in form of Web Components. Later on, when the time comes to use the service we’re creating, we’ll simply import Web Components. That is quite a different approach than what you might be used to. We won’t create a Web Application that calls APIs handled by microservices. We’ll import parts of the front-end from microservices. Our objective is to have a microservice that contains everything; from front-end to back-end. Please refer to the Including Front-End Web Components Into Microservices article for more information that lead to this decision.

I am a huge fan of Test-Driven Development so we’ll write all the code using test first approach. We’ll write a test, run all tests and confirm that the last one fails, write implementation, run all tests and confirm that all passed. Tests will act as executable specifications. We’ll use them to define what should be implemented. If you are new to TDD and the concept of executable documentation, please read the article Tests As Documentation.

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Including Front-End Web Components Into Microservices

Microservices and Front-End

Microservices are becoming more and more popular and many are choosing to transition away from monolithic architecture. However, this approach was mostly limited to back-end services. While it made a lot of sense to split them into smaller independent pieces that can be accessed only through their APIs, same did not apply to front-end. Why is that? I think that the answer lies in technologies we’re using. The way we are developing front-end is not designed to be split into smaller pieces.

Server-side rendering is becoming history. While enterprise might not agree with that statement and continues pushing for server-side frameworks that “magically” transform, for example, Java objects to HTML and JavaScript, client frameworks will continue to increase in popularity slowly sending server-side page rendering into oblivion. That leaves us with client-side frameworks. Single-Page Applications are what we tend to use today. AngularJS, React, ExtJS, ember.js and others proved to be a next step in evolution of front-end development. However, Single-Page Applications or not, most of them are promoting monolithic approach to front-end architecture.

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Server vs client side rendering (AngularJS vs server side MVC)

There’s a lot of discussion related to server vs client side application rendering. While there is no “one choice fits all” solution, I’ll try to argue in favor of client side (specifically AngularJS) from different points of view. First of them is architecture.


Well done architecture has clearly defined separation of concerns (SoS). In most cases minimal high level configuration is:
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Application development: front-end solution with JavaScript

In the previous article we developed the back-end solution for our books application. This article will continue where we stopped.

We’ll develop a front-end solution that can be used with any back-end (Web, mobiles…). You can build on top of the back-end from the previous article (Java, Jersey, Grizzly…) or on top of any other as long as supported services are the same.

The goal of the application is to be able to administer books. In particular, we’ll develop the front-end solution for that application that should be able to:

  • Add new book
  • Update existing book
  • Delete an existing book
  • List all books
  • Display details of the selected book
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