Spring Boot

Spring Boot makes it easy to create Spring-powered, production-grade applications and services with absolute minimum fuss. It takes an opinionated view of the Spring platform so that new and existing users can quickly get to the bits they need.

You can use Spring Boot to create stand-alone Java applications that can be started using java -jar or more traditional WAR deployments. We also provide a command line tool that runs spring scripts.

Our primary goals are:

• Provide a radically faster and widely accessible getting started experience for all Spring development
• Be opinionated out of the box, but get out of the way quickly as requirements start to diverge from the defaults
• Provide a range of non-functional features that are common to large classes of projects (e.g. embedded servers, security, metrics, health checks, externalized configuration)
• Absolutely no code generation and no requirement for XML configuration

Quick Start Script Example

The Spring Zero command line tool uses Groovy underneath so that we can present simple Spring snippets that can 'just run', for example:

@Controller
class ThisWillActuallyRun {
	
	@RequestMapping("/")
	@ResponseBody
	String home() {
		return "Hello World!"
	}
	
}

$ spring run app.groovy
$ curl localhost:8080
Hello World!

See below for command line tool installation instructions.

Quick Start Java Example

If you don't want to use the command line tool, or you would rather work using Java and an IDE you can. Just add a main() method that calls SpringApplication and add @EnableAutoConfiguration:

import org.springframework.boot.*;
import org.springframework.boot.autoconfiguration.*;
import org.springframework.stereotype.*;
import org.springframework.web.bind.annotation.*;

@Controller
@EnableAutoConfiguration
public class SampleController {

	@RequestMapping("/")
	@ResponseBody
	String home() {
		return "Hello World!"
	}

	public static void main(String[] args) throws Exception {
		SpringApplication.run(SampleController.class, args);
	}

}

NOTE: the above example assumes your build system has imported the spring-starter-web maven pom.

Installing the CLI

You need Java SDK v1.6 or higher to run the command line tool. You should check your current Java installation before you begin:

$ java -version

Complete installation instructions TBD. For now you can build from source.

Building from source

Spring Boot can be built with maven v3.0 or above.

$ mvn clean install

You can use an alias for the Spring Boot command line tool:

$ alias spring="java -jar ~/.m2/repository/org/springframework/boot/spring-cli/0.5.0.BUILD-SNAPSHOT/spring-cli-0.5.0.BUILD-SNAPSHOT.jar"

Also see [CONTRIBUTING.md] if you wish to submit pull requests.

Spring Boot Modules

There are a number of modules in Spring Boot. Here are the important ones:

spring-boot

The main library providing features that support the other parts of Spring Boot, these include:

• The SpringApplication class, providing static convenience methods that make it easy to write a stand-alone Spring Application. Its sole job is to create and refresh an appropriate Spring ApplicationContext
• Embedded web applications with a choice of container (Tomcat or Jetty for now)
• First class externalized configuration support
• Convenience ApplicationContext initializers, including support for sensible logging defaults.

See spring-boot/README.md.

spring-boot-autoconfigure

Spring Boot can configure large parts of common applications based on the content of their classpath. A single @EnableAutoConfiguration annotation triggers auto-configuration of the Spring context.

Auto-configuration attempts to deduce which beans a user might need. For example, If 'HSQLDB' is on the classpath, and the user has not configured any database connections, then they probably want an in-memory database to be defined. Auto-configuration will always back away as the user starts to define their own beans.

See spring-boot-autoconfigure/README.md.

spring-boot-starters

Starters are a set of convenient dependency descriptors that you can include in your application. You get a one-stop-shop for all the Spring and related technology that you need without having to hunt through sample code and copy paste loads of dependency descriptors. For example, if you want to get started using Spring and JPA for database access just include the spring-boot-starter-data-jpa dependency in your project, and you are good to go.

See spring-boot-starters/README.md.

spring-boot-cli

The Spring command line application compiles and runs Groovy source, making it super easy to write the absolute minimum of code to get an application running. Spring CLI can also watch files, automatically recompiling and restarting when they change.

See spring-boot-cli/README.md.

spring-boot-actuator

The Actuator uses auto-configuration to decorate your application with features that make it instantly deployable and supportable in production. For instance if you are writing a JSON web service then it will provide a server, security, logging, externalized configuration, management endpoints, an audit abstraction, and more. If you want to switch off the built in features, or extend or replace them, it makes that really easy as well.

See spring-boot-actuator/README.md.

spring-boot-loader

Loader provides the secret sauce that allows you to build a single jar file that can be launched using java -jar. Generally you will not need to use spring-boot-loader directly but instead work with the Gradle or Maven plugin.

See spring-boot-loader/README.md.

Samples

Groovy samples for use with the command line application are available in spring-boot-cli/samples. To run the CLI samples type spring run <sample>.groovy from samples directory.

Java samples are available in spring-boot-samples and should be build with maven and run use java -jar target/<sample>.jar. The following java samples are provided:

• spring-boot-sample-simple - A simple command line application
• spring-boot-sample-tomcat - Embedded Tomcat
• spring-boot-sample-jetty - Embedded Jetty
• spring-boot-sample-actuator - Simple REST service with production features
• spring-boot-sample-actuator-ui - A web UI example with production features
• spring-boot-sample-web-ui - A thymeleaf web application
• spring-boot-sample-web-static - A web application service static files
• spring-sample-batch - Define and run a Batch job in a few lines of code
• spring-sample-data-jpa - Spring Data JPA + Hibernate + HSQLDB
• spring-boot-sample-integration - A spring integration application
• spring-boot-sample-profile - example showing Spring's @profile support
• spring-boot-sample-traditional - shows more traditional WAR packaging (but also executable using java -jar)
• spring-boot-sample-xml - Example show how Spring Boot can be mixed with traditional XML configuration (we generally recommend using Java @Configuration whenever possible)