Getting Started with Spring Boot: Maven Project Setup and a Simple Web Application

Spring Boot is a recent project of the Spring community that aims to simplify the creation of Spring‑based applications and services, offering a convention‑over‑configuration approach similar to Ruby on Rails.

Key features of Spring Boot include fast start‑up experience, zero‑code generation, no XML configuration, embedded servers, security, metrics, health checks, and easy external configuration.

A simple Maven example is presented. First, create a standard Maven project with a src/main/java directory and a pom.xml file. The pom.xml should contain the following content:

<?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.github.abel533</groupId>
    <artifactId>spring-boot</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.0.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <dependencies>
                    <dependency>
                        <groupId>org.springframework</groupId>
                        <artifactId>springloaded</artifactId>
                        <version>1.2.5.RELEASE</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>
</project>

If a project already has its own parent POM, you can import Spring Boot's dependency management instead:

<dependencyManagement>
    <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>1.2.3.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

To use Java 8, add a java.version property inside the <properties> section:

<properties>
    <java.version>1.8</java.version>
</properties>

Add the spring-boot-starter-web starter to enable web functionality, and include the spring-boot-maven-plugin to package the application as an executable JAR. The plugin also supports hot deployment via the springloaded dependency.

Run the project with mvn package to produce an executable JAR, then start it using java -jar xxx.jar. Alternatively, use mvn spring-boot:run for immediate execution.

Create a main application class, for example:

@RestController
@EnableAutoConfiguration
public class Application {

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

    @RequestMapping("/now")
    String now() {
        return "Current time: " + (new Date()).toLocaleString();
    }

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

The @RestController annotation combines @Controller and @ResponseBody, while @EnableAutoConfiguration tells Spring Boot to configure beans automatically based on the classpath. The composite @SpringBootApplication annotation can replace @Configuration, @EnableAutoConfiguration, and @ComponentScan.

To launch the application programmatically, call SpringApplication.run(Application.class, args). Other options include creating a SpringApplication instance or using SpringApplicationBuilder for more complex setups.

When the application starts, Spring Boot initializes an embedded Tomcat server on port 8080, registers the request mappings, and logs the startup sequence, as shown in the sample log output.

For further details, consult the official Spring Boot documentation at http://docs.spring.io/spring-boot/docs/1.2.3.RELEASE/reference/html/index.html .