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

Installation and Getting Started

The reference documentation includes detailed installation instructions as well as a comprehensive ``getting started'' guide. Documentation is published in HTML, PDF and EPUB formats.

Here is a quick teaser of a Spring Boot application:

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

@Controller
@EnableAutoConfiguration
public class Example {

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

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

}

Getting help

Having trouble with Spring Boot, We’d like to help!

• Check the reference documentation, especially the How-to’s — they provide solutions to the most common questions.

• Learn the Spring basics — Spring Boot is builds on many other Spring projects, check the spring.io web-site for a wealth of reference documentation. If you are just starting out with Spring, try one of the guides.

• Ask a questions - we monitor stackoverflow.com for questions tagged with spring-boot.

• Report bugs with Spring Boot at https://github.com/spring-projects/spring-boot/issues.

Building from Source

You don’t need to build from source to use Spring Boot (binaries in repo.spring.io, but if you want to try out the latest and greatest, Spring Boot can be built with maven v3.0.5 or above.

$ mvn clean install

Note	You may need to increase the amount of memory available to Maven by setting a MAVEN_OPTS environment variable with the value -Xmx512m -XX:MaxPermSize=128m

Also see CONTRIBUTING.adoc if you wish to submit pull requests, and in particular please fill out the Contributor’s Agreement before your first change however trivial. (Or if you filed such an agreement already for another project just mention that in your pull request.)

Modules

There are a number of modules in Spring Boot, here is a quick overview:

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

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.

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.

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.

spring-boot-actuator

Spring Boot Actuator provides additional 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.

spring-boot-loader

Spring Boot 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.

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 built with maven and run by invoking 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-boot-sample-batch — Define and run a Batch job in a few lines of code

• spring-boot-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)

Guides

The spring.io site contains several guides that show how to use Spring Boot step-by-step:

• Building an Application with Spring Boot is a very basic guide that shows you how to create a simple application, run it and add some management services.

• Building a RESTful Web Service with Spring Boot Actuator is a guide to creating a REST web service and also shows how the server can be configured.

• Converting a Spring Boot JAR Application to a WAR shows you how to run applications in a web server as a WAR file.