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

Spring Boot CLI

The Spring Boot CLI is a command line tool that can be used if you want to quickly prototype with Spring. It allows you to run Groovy scripts, which means that you have a familiar Java-like syntax, without so much boilerplate code.

You don't need to use the CLI to work with Spring Boot but it's definitely the quickest way to get a Spring application off the ground.

Note: If you don't want to use the CLI, jump ahead to the Java example.

Installing the CLI

You need Java SDK v1.6 or higher to run the command line tool (there are even some issues with the 1.7.0_25 build of openjdk, so stick to earlier builds or use 1.6 for preference). You should check your current Java installation before you begin:

$ java -version

Manual installation

You can download the Spring CLI distribution from the Spring software repository:

• spring-boot-cli-0.5.0.M5-bin.zip
• spring-boot-cli-0.5.0.M5-bin.tar.gz

Cutting edge snapshot distributions are also available.

Once downloaded, follow the INSTALL instructions from the unpacked archive. In summary: there is a spring script (spring.bat for Windows) in a bin/ directory in the .zip file, or alternatively you can use java -jar with the .jar file (the script helps you to be sure that the classpath is set correctly).

Installation with GVM

GVM (the Groovy Environment Manager) can be used for managing multiple versions of verious Groovy and Java binary packages, including Groovy itself and the Spring Boot CLI. Get gvm from the gvm home page and install Spring Boot with

$ gvm install springboot
$ spring --version
Spring Boot v0.5.0.M5

Note: If you are developing features for the CLI and want easy access to the version you just built, follow these extra instructions.

$ gvm install springboot dev /path/to/spring-boot/spring-boot-cli/target/spring-boot-cli-0.5.0.BUILD-SNAPSHOT-bin/spring-0.5.0.BUILD-SNAPSHOT/
$ gvm use springboot dev
$ spring --version
Spring CLI v0.5.0.BUILD-SNAPSHOT

This will install a local instance of spring called the dev instance inside your gvm repository. It points at your target build location, so every time you rebuild Spring Boot, spring will be up-to-date.

You can see it by doing this:

$ gvm ls springboot

================================================================================
Available Springboot Versions
================================================================================
 > + dev                                                                           
   * 0.5.0.M5                                                                      

================================================================================
+ - local version
* - installed
> - currently in use
================================================================================

OSX Homebrew installation

If you are on a Mac and using homebrew, all you need to do to install the Spring Boot CLI is:

$ brew install http://repo.spring.io/install/springboot.rb

Homebrew will install spring to /usr/local/bin. Now you can jump right to a quick start example.

Note: If you don't see the formula, you're installation of brew might be out-of-date. Just execute brew update and try again.

Quick start script example

Here's a really simple web application. Create a file called app.groovy:

@Controller
class ThisWillActuallyRun {

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

}

Then run it from a shell:

$ spring run app.groovy

Note: It will take some time when you first run the application as dependencies are downloaded, subsequent runs will be much quicker.

Open http://localhost:8080 in your favorite web browser and you should see the following output:

Hello World!

Spring Boot with Java

If you don't want to use the command line tool, or you would rather work using Java and an IDE you can. Here is how you build the same example using Java.

Quick start Maven POM

You will need to install Apache Maven v3.0.5 or above to build this example.

Create a pom.xml to import the appropriate Spring Boot starters:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.example</groupId>
	<artifactId>myproject</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<!-- Inherit defaults from Spring Boot -->
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>0.5.0.M5</version>
	</parent>

	<!-- Add typical dependencies for a web application -->
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>

	<!-- Package as an executable JAR -->
	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

	<!-- Allow access to Spring milestones and snapshots -->
	<!-- (you don't need this if you are using anything after 0.5.0.RELEASE) -->
	<repositories>
		<repository>
			<id>spring-snapshots</id>
			<url>http://repo.spring.io/snapshot</url>
			<snapshots><enabled>true</enabled></snapshots>
		</repository>
		<repository>
			<id>spring-milestones</id>
			<url>http://repo.spring.io/milestone</url>
			<snapshots><enabled>true</enabled></snapshots>
		</repository>
	</repositories>
	<pluginRepositories>
		<pluginRepository>
			<id>spring-snapshots</id>
			<url>http://repo.spring.io/snapshot</url>
		</pluginRepository>
		<pluginRepository>
			<id>spring-milestones</id>
			<url>http://repo.spring.io/milestone</url>
		</pluginRepository>
	</pluginRepositories>
</project>

Note: If you prefer Gradle as your build system, we provide a plugin that can help you package an executable JAR.

Quick start Java example

Here is the main class for a simple web application (just save the content to src/main/java/SampleController.java):

import org.springframework.boot.*;
import org.springframework.boot.autoconfigure.*;
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);
	}
}

Other than import statements, the main difference between this example and the earlier Groovy script is the main() method that calls SpringApplication and the @EnableAutoConfiguration annotation.

You can run this application by building a jar and executing it:

$ mvn package
$ java -jar target/myproject-0.0.1-SNAPSHOT.jar

Open http://localhost:8080 in your favorite web browser and you should see the following output:

Hello World!

Building Spring Boot from source

You don't need to build from source to use Spring Boot (it's 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.md if you wish to submit pull requests.

Further Reading

There are a number of modules in Spring Boot, if you want learn more about each one please refer to the appropriate README.md file:

Note: We are currently still working on documentation for Spring Boot.

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

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.

See spring-boot-actuator/README.md.

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.

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-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.