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 a toolkit and runtime platform 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 no 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 behaviour 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

3. Get to Work!

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

What? It's Groovy then? or like Grails? or Roo?

There is a command line tool that uses Groovy underneath so that we can present simple snippets that can just run just like the slimline app.groovy example above. Groovy makes this really easy.

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);
	}

}

Spring Zero Themes

There are a number of themes 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.

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)

Spring Autoconfigure

Spring Zero can configure large parts of common applications based on detecting the content of the classpath and any existing application context:

• @EnableAutoConfigure is an annotation that 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.
• @Conditional is an annotation in Spring 4.0 that allows you to control which parts of an application are used at runtime. Spring Zero provides some concrete implementations of conditional configuration, e.g. @ConditionalOnBean, @ConditionalOnMissingBean and @ConditionalOnClass.

Spring Actuator

Spring Actuator uses auto-configuration features 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.

Service Wrappers and Deployability

Spring Zero helps you to take that last step from finishing a development iteration to getting the code running in production. Without having to think too much about it, other than choosing your deployment environment (CentOS, Ubuntu, Windows etc) you should be able to stand up an instance, or multiple instances, of your component and have them fit seamlessly into the operating system environment.

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.

Building the code

Use maven to build the source code.

$ mvn clean install

Importing into eclipse

You can use m2e or maven eclipse:eclipse.

Project specific settings are configured for source formatting. If you are using m2e you can follow these steps to install eclipse support for formatting:

• Select Install new software from the help menu
• Click Add... to add a new repository
• Click the Archive... button
• Select org.eclipse.m2e.maveneclipse.site-0.0.1-SNAPSHOT-site.zip from the eclipse folder in this checkout
• Install "Maven Integration for the maven-eclipse-plugin"

Or if you prefer you can import settings manually from the /eclipse folder.

Samples

The following samples are included. To run use java -jar target/<archive>.jar

• spring-zero-simple-sample - A simple command line application
• spring-zero-jetty-sample - Embedded Jetty
• spring-zero-tomcat-sample - Embedded Tomcat
• spring-zero-service-sample - Simple REST service with production features
• spring-batch-sample - Define and run a Batch job in a few lines of code
• spring-zero-data-sample - Spring Data JPA + Hibernate + HSQLDB