Different Ways to Running Spring Boot Application - RameshMF/spring-boot-developers-guide GitHub Wiki

In this article, we will discuss different ways to running Spring Boot application.

One of the biggest advantages of packaging your application as a jar and using an embedded HTTP server is that you can run your application as you would any other. Debugging Spring Boot applications is also easy. You do not need any special IDE plugins or extensions.

1. Running from an IDE
2. Running as a Packaged Application
3. Using the Maven Plugin
4. Using External Tomcat
5. Using the Gradle Plugin

You can run a Spring Boot application from your IDE as a simple Java application (Application.java or Main class).

1. There are many ways to create a Spring Boot application. The simplest way is to use Spring Initializr at http://start.spring.io/, which is an online Spring Boot application generator.
2. Once the Spring Boot project has generated. We need to import our project, import steps vary depending on your IDE and build system. Most IDEs can import Maven projects directly. For example, Eclipse users can select Import… → Existing Maven Projects from the File menu.
3. If you cannot directly import your project into your IDE, you may be able to generate IDE metadata by using a build plugin. Maven includes plugins for Eclipse and IDEA. Gradle offers plugins for various IDEs.

Note: If you accidentally run a web application twice, you see a “Port already in use” error. STS users can use the Relaunch button rather than the Run button to ensure that any existing instance is closed.

If you use the Spring Boot Maven or Gradle plugins to create an executable jar, you can run your application using java -jar. For example, change directory to the current project directory and run following command in cmd.

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

It is also possible to run a packaged application with remote debugging support enabled. Doing so lets you attach a debugger to your 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

The Spring Boot Maven plugin includes a run goal that can be used to quickly compile and run your application. Applications run in an exploded form, as they do in your IDE. The following example shows a typical Maven command to run a Spring Boot application:

$ mvn spring-boot:run

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

$ export MAVEN_OPTS=-Xmx1024m

We can also deploy Spring Boot web application WAR file to the external Tomcat servlet container. There are three steps we can follow to create a war file and deploy in external Tomcat servlet container

<packaging>war</packaging>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-tomcat</artifactId>
			<scope>provided</scope>
		</dependency>

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;

@SpringBootApplication
public class Application extends SpringBootServletInitializer{

	@Override
	protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
		return application.sources(Application.class);
	}
	
	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
}

The Spring Boot Gradle plugin also includes a bootRun task that can be used to run your application in an exploded form. The bootRun task is added whenever you apply the org.springframework.boot and java plugins and is shown in the following example:

$ gradle bootRun

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

$ export JAVA_OPTS=-Xmx1024m