A good service always validates data before processing it. In this section, we will look at the ;Bean Validation API and use its reference implementation to implement validation in our services.

The Bean Validation API provides a number of annotations that can be used to validate beans. The ;JSR 349 ;specification defines Bean Validation API 1.1. Hibernate-validator is the reference implementation. ;Both are already defined as dependencies in the spring-boot-web-starter project:

• hibernate-validator-5.2.4.Final.jar
• validation-api-1.1.0.Final.jar

We will create a simple validation for the createTodo service method.

Creating validations involves two steps:

1. Enabling validation on the controller method.
2. Adding validations on the bean.