Spring Initializr is a tool that bootstraps your Spring Boot projects. This Spring Boot feature powers project creation through cURL, multiple IDEs, and its very own Spring CLI. It doesn’t generate any application code but provides a basic project structure. All you need to do is write the application code. 

Spring Initializr allows you to select a project, the programming language of your choice, and add dependencies such as dev tools, actuator, web, etc. Generating a project is as quick as clicking the Generate button after selecting the options provided on the Spring Initializr screen.

For example, the generated project includes the Gradle build specification or pom.xml on selecting the Gradle or Maven project, respectively. Also, it consists of a class with a main () method to bootstrap the application. There is an application context that uses the Spring Boot auto-configuration and empty properties file so you can add configuration properties.

2. Spring CLI

3. Autoconfiguration 

Imagine you want to create a new library that you want to use at various places in your application. You may be able to develop and integrate the code; however, you may still be required to manually do a lot of configuration. It is here that the autoconfiguration feature provided by Spring Boot comes into the picture.

While creating a new project, Spring Boot allows you to choose dependencies for your project. It is these dependencies, based on which the autoconfiguration feature loads specific default configurations. The AutoConfiguration class is fortified with @Conditional annotations that activate beans in particular circumstances. Spring Boot evaluates these conditionals during the startup of an application.

Refer to reference documentation to learn conditional annotations provided by Spring. If these conditions are not enough for our use case, you can create your own custom conditions.

To use autoconfiguration, you will need to use @EnableAutoConfiguration or @SpringBootApplication annotations.

A file called spring. Factories automatically load during boot-up. It contains the reference to many configuration classes. The file is located in META-INF/spring.factories of the dependency org.springframework.boot:spring-boot-autoconfigure.

While a plethora of classes are available for use, you can remove them by using the exclude feature of @EnableAutoConfiguration.

4. Externalized Configuration

In Spring Boot applications, all configuration parameters are read from either application.properties or application.yaml resource file. However, there may be cases when you may want to move your configuration from one environment to another. This is when you may have to configure these properties for which you will be required to rebuild and retest your application in all environments. Not only that, every time a change happens, you will also have to redeploy your application in the production environment.

To overcome this problem, Spring Boot enables you to externalize your configuration. Externalizing the configuration means using the application code that you use in one environment in an external environment. Spring Boot lets you externalize your configuration so you can reuse your code in diverse environments. The following files can be used to externalize configuration:

• Properties files
• YAML files
• Environment variables, etc.

To debug your application and analyze logs, you may need to understand what is happening inside the application. For example, which beans are configured, the number of times a specific service was called, or the number of times a specific service failed. The actuator is the window into your application. The Actuator framework is a lightweight framework that you can use without installing another application or tool to inspect your application health-check endpoints. Spring Actuator provides an easy way to track health, metrics, info, and so on.

Besides monitoring, Actuator endpoints enable you to interact with your application. Spring Boot includes several built-in endpoints, and you can also add your own actuator implementations.