Starters are simplified dependency descriptors customized for different purposes. For example, spring-boot-starter-web is the starter for building web application, including RESTful, using Spring MVC. It uses Tomcat as the default embedded container. If I want to develop a web application using Spring MVC, all we would need to do is include spring-boot-starter-web in our dependencies, and we get the following automatically pre-configured:

• Spring MVC
• Compatible versions of jackson-databind (for binding) and hibernate-validator (for form validation)
• spring-boot-starter-tomcat (starter project for Tomcat)

The following code snippet shows some of the dependencies configured in spring-boot-starter-web:

    <dependencies>
        <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-tomcat</artifactId>
        </dependency>
        <dependency>
          <groupId>org.hibernate</groupId>
          <artifactId>hibernate-validator</artifactId>
        </dependency>
        <dependency>
          <groupId>com.fasterxml.jackson.core</groupId>
          <artifactId>jackson-databind</artifactId>
        </dependency>
        <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-web</artifactId>
        </dependency>
        <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-webmvc</artifactId>
       </dependency>
    </dependencies>

As we can see in the preceding snippet, when we use
spring-boot-starter-web, we get a lot of frameworks auto-configured.

For the web application we would like to build, we would also want to do some good unit testing and deploy it on Tomcat. The following snippet shows the different starter dependencies that we would need. We would need to add this to our pom.xml file:

    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
     </dependency>
     <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-test</artifactId>
       <scope>test</scope>
     </dependency>
     <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-tomcat</artifactId>
       <scope>provided</scope>
     </dependency>
    </dependencies>

We add three starter projects:

• We've already discussed spring-boot-starter-web. It provides us with the frameworks needed to build a web application with Spring MVC.
• The spring-boot-starter-test dependency provides the following test frameworks needed for unit testing:
  • JUnit: Basic unit test framework
  • Mockito: For mocking
  • Hamcrest, AssertJ: For readable asserts
  • Spring Test: A unit testing framework for spring-context based applications
• The spring-boot-starter-tomcat dependency is the default for running web applications. We include it for clarity. spring-boot-starter-tomcat is the starter for using Tomcat as the embedded servlet container.

We now have our pom.xml file configured with the starter parent and the required starter projects. Let's add spring-boot-maven-plugin now, which would enable us to run Spring Boot applications.