Launching the application

Many Spring Boot developers want their applications to use auto-configuration, component scanning, and the ability to define additional configuration in their "application class". To activate these three functions, you can use a single annotation @SpringBootApplication:

• @EnableAutoConfiguration: Enables the Spring Boot autoconfiguration mechanism

• @ComponentScan: Enables scanning of the @Component annotation for the package in which the application is located

• @SpringBootConfiguration: Allows you to register additional beans in the context or import additional configuration classes. An alternative to the standard @Configuration annotation from Spring that helps discover configurations in your integration tests.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
// Same as @SpringBootConfiguration, @EnableAutoConfiguration, @ComponentScan
@SpringBootApplication
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
// same as @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan
@SpringBootApplication
class MyApplication
fun main(args: Array<String>) {
    runApplication<MyApplication>(*args)
}

import org.springframework.boot.SpringApplication;
import org.springframework.boot.SpringBootConfiguration;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.Import;
@SpringBootConfiguration(proxyBeanMethods = false)
@EnableAutoConfiguration
@Import({ SomeConfiguration.class, AnotherConfiguration.class })
public class MyApplication {
    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }
}

import org.springframework.boot.SpringBootConfiguration
import org.springframework.boot.autoconfigure.EnableAutoConfiguration
import org.springframework.boot.docs.using.structuringyourcode.locatingthemainclass.MyApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Import
@SpringBootConfiguration(proxyBeanMethods = false)
@EnableAutoConfiguration
@Import(SomeConfiguration::class, AnotherConfiguration::class)
class MyApplication
fun main(args: Array<String>) {
    runApplication<MyApplication>(*args)
}

Running your application

One of the biggest benefits of packaging your application as a jar file and using the built-in HTTP server is that you can run your application just like any other. This sample is used to debug applications in Spring Boot. You don't need any special plugins or extensions for the IDE.

Execution from IDE

You can run a Spring Boot application from your IDE as a Java application. However, you must first import the project. The import steps depend on your IDE and build system. Most IDEs are capable of importing Maven projects directly. For example, Eclipse users can select Import...​ → Existing Maven Projects from the File menu.

If you can't directly import your project into the IDE, you can generate IDE metadata using the build plugin. Maven includes plugins for Eclipse and IDEA. Gradle provides plugins for various IDEs.

Execution as a packaged application

If you are using the Spring Boot plugins for Maven or Gradle to create an executable jar file, you can run your application using the java -jar command, as shown in the following example:

$ java -jar target/myapplication-0.0.1-SNAPSHOT.jar

You can also run a packaged application with remote debugging enabled. This allows you to attach a debugger to a packaged application, as shown in the following example:

$ java -Xdebug -Xrunjdwp:server=y,transport=dt_socket,address=8000,suspend=n \
       -jar target/myapplication-0.0.1-SNAPSHOT.jar

Using the Maven plugin

The Spring Boot Maven plugin includes a run target that you can use to quickly compile and run your application. Applications run in disassembled form, just like in your IDE. The following example shows a typical Maven command to run a Spring Boot application:

$ mvn spring-boot:run

You can also use the operating system environment variable MAVEN_OPTS, as shown in the following example:

$ export MAVEN_OPTS=-Xmx1024m

Using the Gradle plugin

The Spring Boot Gradle plugin also contains a bootRun task that can be used to run the application out of the box. The bootRun task is added whenever you use the org.springframework.boot and java plugins, and is shown in the following example:

$ gradle bootRun

You can also use the operating system environment variable JAVA_OPTS, as shown in the following example:

$ export JAVA_OPTS=-Xmx1024m

Hot swap

Since Spring Boot applications are regular Java applications, JVM hot swapping should work out of the box. Hot swapping in the JVM is somewhat limited in the bytecode it can replace. As a more complete solution, you can use JRebel.

The spring-boot-devtools module also contains support for quickly restarting applications.