Spring Zero

Spring Zero is "Spring for Snowboarders". If you are kewl, or just impatient, and you want to use Spring, then this is the place to be. Spring Zero is the code-name for a group of related technologies, that will get you up and running with Spring-powered, production-grade applications and services with absolute minimum fuss. It takes an opinionated view of the Spring family so that new and existing users can quickly get to the bits they need. Assumes limited knowledge of the Java development ecosystem. Absolutely no code generation and no XML (unless you really want it).

The goals are:

• Radically faster and widely accessible getting started experience for 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)
• First class support for REST-ful services, modern web applications, batch jobs, and enterprise integration
• Applications that adapt their behavior or configuration to their environment
• Optionally use Groovy features like DSLs and AST transformations to accelerate the implementation of basic business requirements

Installing

You need to build from source for now, but when it's done instructions will look like this:

1. Get Java. Download and install the Java SDK from www.java.com

2. Get Spring

   $ curl -s spring.cfapps.io/installer | bash

   or use the Windows installer

Building from source

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

$ mvn clean install

An alias can be used for the Spring Zero command line tool:

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

Also see CONTRIBUTING.md if you want to submit pull requests.

Quick Start Example

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

$ cat > app.groovy
@Controller
class ThisWillActuallyRun {
	@RequestMapping("/")
	@ResponseBody
	String home() {
		return "Hello World!"
	}
}
<ctrl-d>
$ spr run app.groovy
$ curl localhost:8080
Hello World!

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.stereotype.*;
import org.springframework.web.bind.annotation.*;
import org.springframework.bootstrap.context.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.

Spring Zero Components

There are a number of components in Zero. Here are the important ones:

The Spring 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-cli/README.md.

Spring Bootstrap

The main library providing features that support the other parts of Spring Zero. Features include:

• SpringApplication - a class with static convenience methods that make it really easy to write a standalone 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

See spring-bootstrap/README.md.

Spring Autoconfigure

Spring Zero can configure large parts of common applications based on detecting the content of the classpath and any existing application context. A single @EnableAutoConfigure annotation triggers auto-configuration of the Spring context.

Auto-configuration attempts to guess what beans a user might want based on their classpath. For example, If a 'HSQLDB' is on the classpath the user probably wants an in-memory database to be defined. Auto-configuration will back away as the user starts to define their own beans.

See spring-autoconfigure/README.md.

Spring Actuator

Spring 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-actuator/README.md.

Spring Starters

Spring 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 one dependency in your project, and you are good to go.

See spring-starters/README.md.

Packaging

The spring-launcher and spring-maven-packaging-plugin provide a convenient way to package you application for release. Applications can be released as a single jar file that can simply be launched using java -jar.

See spring-launcher/README.md & spring-package-maven-plugin/README.md.

Samples

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

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

• spring-zero-sample-simple - A simple command line application
• spring-zero-sample-tomcat - Embedded Tomcat
• spring-zero-sample-jetty - Embedded Jetty
• spring-zero-sample-actuator - Simple REST service with production features
• spring-zero-sample-actuator-ui - A web UI example with production features
• spring-zero-sample-web-ui - A thymeleaf web application
• 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-zero-sample-integration - A spring integration application
• spring-zero-sample-profile - example showing Spring's @profile support
• spring-zero-sample-traditional - shows Spring Zero with more traditional WAR packaging (but also executable using java -jar)
• spring-zero-sample-xml - Example show how Spring Zero can be mixed with trditional XML configuration