Exploring Micro-Frameworks: Spring Boot

Spring Boot is a brand new framework from the team at Pivotal, designed to simplify the bootstrapping and development of a new Spring application. The framework takes an opinionated approach to configuration, freeing developers from the need to define boilerplate configuration. In that, Boot aims to be a front-runner in the ever-expanding rapid application development space.

The Spring IO platform has been criticized over the years for having bulky XML configuration with complex dependency management. During last year’s Spring One 2GX conference, Pivotal CTO, Adrian Colyer acknowledged those criticisms, and made special note that a goal of the platform going forward is to embrace an XML-free development experience. Boot takes that mission statement to the extreme, not only freeing developers from the need for XML, but also, in some scenarios, releasing them from the tedium of writing import statements. In the days following its public beta release, Boot gained some viral popularity by demonstrating the framework’s simplicity with a runnable web application that fit in under 140-characters, delivered in a tweet Spring boot course.

Installing Boot

At its most fundamental level, Spring Boot is little more than a set of libraries that can be leveraged by any project’s build system. As a convenience, the framework also offers a command-line interface, which can be used to run and test Boot applications. The framework distribution, including the integrated CLI, can be manually downloaded and installed from the Spring repository. A more convenient approach is to use the Groovy enVironment Manager (GVM), which will handle the installation and management of Boot versions. Boot and its CLI can be installed by GVM with the command line, gvm install springboot. Formulas are available for installing Boot on OS X through the Homebrew package manager. To do so, first tap the Pivotal repository with brew tap pivotal/tap, followed by the brew install springboot command Spring boot online course.

Projects that are to be packaged and distributed will need to rely on build systems like Maven or Gradle. To simplify the dependency graph, Boot’s functionality is modularized, and groups of dependencies can be brought in to a project by importing Boot’s so-called "starter" modules. To easily manage dependency versions and to make use of default configuration, the framework exposes a parent POM, which can be inherited by projects. An example POM for a Spring Boot project is defined in Listing 1.

Developing a Spring Boot Application

The most popular example of a Spring Boot application is one that was delivered via Twitter shortly following the public announcement of the framework. As demonstrated in its entirety in Listing 1.2, a very simple Groovy file can be crafted into a powerful Spring-backed web application.

This application can be run from the Spring Boot CLI, by executing the spring run App.groovy command. Boot analyzes the file and — through various identifiers known as "compiler auto-configuration" — determines that it is intended to be a web application. It then, in turn, bootstraps the Spring Application context inside of an embedded Tomcat container on the default port of 8080. Opening a browser and navigating to the provided URL will land you on a page with a simple text response, "hello". This process of providing a default application context and embedded container allows developers to focus on the process of developing application and business logic, and frees them from the tedium of otherwise boiler-plate configuration Spring boot online training india.

Boot’s ability to ascertain the desired functionality of a class is what makes it such a powerful tool for rapid application development. When applications are executed from the Boot CLI, they are built using the internal Groovy compiler, which allows the ability to programmatically inspect and modify a class while its bytecode is being generated. In this way, developers who use the CLI are not only freed from the need to define default configuration, but, to an extent, they also do not need to define certain import statements that can otherwise be recognized and automatically added during the compilation process. Additionally, when applications are run from the CLI, Groovy’s built-in dependency manager, "Grape", is used to resolve classpath dependencies that are needed to bootstrap the compilation and runtime environments, as determined by Boot’s compiler auto-configuration mechanisms. This idiom not only makes the framework more user-friendly, but also allows different versions of Spring Boot to be coupled with specific versions of libraries from the Spring IO platform, which in turn means that developers do not need to be concerned with managing a complex dependency graph and versioning structure. Additionally, it opens the door for rapid prototyping and quick generation of proof-of-concept project code.

For projects that are not built with the CLI, Boot provides a host of "starter" modules, which define a set of dependencies that can be brought into a build system in order to resolve the specific libraries needed from the framework and its parent platform. As an example of this, the spring-boot-starter-actuator dependency pulls in a set of base Spring projects to get an application quickly configured and up-and-running. The emphasis of this dependency is on developing web applications, and specifically RESTful web services. When included in conjunction with the spring-boot-starter-web dependency, it will provide auto-configuration to bootstrap an embedded Tomcat container, and will map endpoints useful to micro-service applications, like server information, application metrics, and environment details. Additionally, when the spring-boot-starter-security module is brought in, the actuator will auto-configure Spring Security to provide the application with basic authentication and other advanced security features. For any application structure, it will also include an internal auditing framework that can be used for reporting purposes or application-specific needs, like developing an authenitcation-failure lock-out policy.

To demonstrate quickly getting a Spring web application up-and-running from within a Java Maven project Spring boot online training.