spring-boot/spring-bootstrap

Spring Bootstrap

Spring Bootstrap provides features for the other parts of Spring Zero. It is relatively unopinionated and therefore usable as a standalone library for anyone whose tastes diverge from ours.

Feature	Implementation	Notes
Launch Spring from Java main	SpringApplication	Plenty of convenience methods and customization opportunities
Server	Tomcat or Jetty
Logging	Logback, Log4j or JDK	Sensible defaults configurations.
Externalized configuration	Properties or YAML	Support for Spring profiles. Bind automatically to @Bean.

For a quick introduction and to get started quickly with a new project, carry on reading. For more in depth coverage of the features of Spring Zero Actuator, go to the Feature Guide.

Getting Started

You will need Java (6 at least) and a build tool (Maven is what we use below, but you are more than welcome to use gradle). These can be downloaded or installed easily in most operating systems. For Ubuntu:

$ sudo apt-get install openjdk-6-jdk maven

A basic project

If you are using Maven create a really simple pom.xml with 2 dependencies:

pom.xml

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany</groupId>
  <artifactId>myproject</artifactId>
  <version>1.0.0-SNAPSHOT</version>
  <packaging>jar</packaging>
  <properties>
      <start-class>com.mycompany.Application</start-class>
  </properties>
  <parent>
    <groupId>org.springframework.zero</groupId>
    <artifactId>spring-starter-parent</artifactId>
    <version>{{project.version}}</version>
  </parent>
  <dependencies>
    <dependency>
      <groupId>org.springframework.zero</groupId>
      <artifactId>spring-starter</artifactId>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.zero</groupId>
        <artifactId>spring-package-maven-plugin</artifactId>
     </plugin>
    </plugins>
  </build>
</project>

If you like Gradle, that's fine, and you will know what to do with those dependencies. The one dependency adds Spring Zero auto configuration and the Tomcat container to your application. If you prefer Jetty you can just add the embedded Jetty jars to your classpath instead of Tomcat.

Now write a simple main class

Application.java

package com.mycompany;

import org.springframework.bootstrap.SpringApplication;
import org.springframework.context.annotation.Configuration;

@Configuration
public class Application {

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

}

You should be able to run it already:

$ mvn package
$ java -jar target/myproject-1.0.0-SNAPSHOT.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 Spring Bootstrap

2013-07-19 17:13:51.673  INFO 18937 --- [           main] com.mycompany.Application ...
... <logs showing application starting up>

It doesn't do anything yet, but that's because all we did is start a Spring ApplicationContext and let it close when the JVM stopped.

To make it do something a little bit more interesting you could bind some command line arguments to the application:

Application.java

@Configuration
@ConfigurationProperties
@EnableConfigurationProperties
public class Application {

    private String message;

    @Override
    public void run(String... args) throws Exception {
    	System.err.println(message);
    }

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
    
 	public String getMessage() {
		return message;
	}

	public void setMessage(String message) {
		this.message = message;
	}
}

The @ConfigurationProperties annotation binds the Spring Environment (including command line arguments) to the Application instance, and CommandLineRunner is a marker interface for anything you want to be executed after the content is started. So run it again and you will see the message:

    $ mvn package
    $ java -jar target/myproject-1.0.0-SNAPSHOT.jar --message="Hello World"
    ...
    Hello World

To add more features, add some @Bean definitions to your Application class, and read more in the Feature Guide.