Packaging, Running, and Building Spring Boot Apps

Table of Contents

1. Introduction
2. Packaging Spring Boot Applications
   • JAR vs WAR
   • Spring Boot Maven Plugin
   • Spring Boot Gradle Plugin
3. Running Spring Boot Applications
4. Building Spring Boot Applications
5. Customizing Build Process
6. Dockerizing Spring Boot Applications
7. Deploying Spring Boot Applications
8. Conclusion

1. Introduction

Spring Boot makes it easy to develop and deploy Java applications. One of its strengths is how it simplifies the packaging, running, and building processes. Whether you’re deploying to a local machine or a cloud environment, Spring Boot provides tools and configuration to automate and optimize these tasks.

This module will walk you through the steps involved in packaging, running, and building Spring Boot applications, covering Maven, Gradle, and deployment options.

2. Packaging Spring Boot Applications

JAR vs WAR

Spring Boot allows you to package applications into two main formats: JAR (Java ARchive) and WAR (Web Application Archive).

• JAR: Typically used when you want to run the application as a standalone Java application with an embedded server like Tomcat, Jetty, or Undertow.
• WAR: Used if you want to deploy your application to an external web server like Apache Tomcat or JBoss.

How to specify the packaging format in pom.xml (for Maven):

xmlCopyEdit<packaging>jar</packaging>

Or for WAR:

xmlCopyEdit<packaging>war</packaging>

Spring Boot defaults to JAR packaging unless specified otherwise.

How to specify the packaging format in build.gradle (for Gradle):

groovyCopyEditbootJar {
    baseName = 'myapp'
    version = '0.1.0'
}

Or for WAR:

groovyCopyEditbootWar {
    baseName = 'myapp'
    version = '0.1.0'
}

Spring Boot Maven Plugin

Spring Boot includes a Maven plugin to simplify packaging and running applications. Add the following plugin to your pom.xml:

xmlCopyEdit<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

This plugin allows you to:

• Build your Spring Boot application
• Run the application using the mvn spring-boot:run command
• Create executable JAR or WAR files

To build the JAR file:

bashCopyEditmvn clean package

This will create a .jar file in the target directory.

Spring Boot Gradle Plugin

For Gradle, include the following in your build.gradle:

groovyCopyEditplugins {
    id 'org.springframework.boot' version '2.x.x'
    id 'java'
}

To package the application, run:

bashCopyEdit./gradlew build

This will generate the .jar file in the build/libs directory.

3. Running Spring Boot Applications

Once your application is packaged, running it is simple.

For Maven:

bashCopyEditmvn spring-boot:run

For Gradle:

bashCopyEdit./gradlew bootRun

Alternatively, you can run the generated JAR file using:

bashCopyEditjava -jar target/myapp-0.1.0.jar

Spring Boot’s embedded server (like Tomcat) will start, and you can access the application via http://localhost:8080 (or another port if configured).

4. Building Spring Boot Applications

Building Spring Boot applications is straightforward using Maven or Gradle.

Maven Build Command

For a full build, use:

bashCopyEditmvn clean install

This will clean the existing builds and install the application into your local Maven repository.

Gradle Build Command

With Gradle, the equivalent command is:

bashCopyEdit./gradlew clean build

This will clean the build, recompile the code, run tests, and package the application.

5. Customizing Build Process

You can customize the build process to include additional tasks, dependencies, or configuration properties.

For Maven

In pom.xml, customize the build and plugin sections:

xmlCopyEdit<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

For Gradle

In build.gradle, customize tasks such as adding custom build configurations or dependency resolution.

groovyCopyEditbootJar {
    archiveFileName = 'myapp.jar'
    mainClassName = 'com.example.MyApplication'
}

6. Dockerizing Spring Boot Applications

Spring Boot applications are well-suited for containerization. Docker allows you to package your application with its environment and dependencies in a standardized unit, ensuring it runs consistently across different platforms.

To Dockerize a Spring Boot app:

1. Create a Dockerfile in the root of your project:

dockerfileCopyEditFROM openjdk:11-jdk
COPY target/myapp-0.1.0.jar myapp.jar
ENTRYPOINT ["java", "-jar", "myapp.jar"]

2. Build the Docker image:

bashCopyEditdocker build -t myapp .

3. Run the Docker container:

bashCopyEditdocker run -p 8080:8080 myapp

Now your Spring Boot application will be available at http://localhost:8080 inside the Docker container.

7. Deploying Spring Boot Applications

Spring Boot applications can be deployed in various environments, including cloud platforms like AWS, Azure, and Google Cloud, or on on-premises servers.

Deploy to Cloud (Example: AWS)

1. Package your application as a JAR file.
2. Upload the JAR to an AWS EC2 instance.
3. SSH into the EC2 instance and run the application:

bashCopyEditjava -jar myapp-0.1.0.jar

You can use tools like Elastic Beanstalk for automated deployments on AWS.

8. Conclusion

Spring Boot provides powerful tools for packaging, running, and building applications with ease. The combination of embedded servers, Maven/Gradle plugins, and Docker support makes it a flexible and modern solution for both local and cloud-based deployments. By mastering the build and deployment processes, you can streamline your development and deployment workflows, ensuring rapid iteration and robust production environments.