Forms are the basic elements of a web application, and data validation is the most basic security mechanism in a web application. User input must always be validated before being processed. We will start the implementation of TaskAgile from the register page. In this chapter, we will focus on building the registration form and validating inputs on both the frontend and the backend. Along the way, we will practice TDD while we're building the register page and keep recording the code commits so that you can check the details of each step easily.

In this chapter, you will learn the following:

• How to build a UI with Bootstrap 4
• How to build forms with Vue.js
• How to validate on the frontend with Vuelidate
• How to validate on the backend with Bean Validation
• How to implement registration in the domain model
• How to do full set unit testing

We have a lot to accomplish in this chapter. Let's get started.