Quick start guide to Docker and Spring Boot: Get started quickly with containerized application development

Quick Start Guide for Docker and Spring Boot: Quickly Get Started with Containerized Application Development

In today's software development and deployment environment, containerized application development has become more and more important. becoming more and more common. Containerization allows developers to package an application and its dependencies into a self-contained, portable container, allowing for fast, consistent, and reliable deployment.

Docker is one of the most popular containerization platforms, providing a powerful tooling and ecosystem to simplify the creation, management and deployment of containers. Spring Boot is a framework for rapid development of Java-based applications that makes it very easy to build independent and deployable microservices. Combining Docker and Spring Boot, we can develop and deploy containerized applications more conveniently.

This article will guide you to quickly get started with containerized application development with Docker and Spring Boot. We'll start by installing Docker, creating a simple Spring Boot application, and packaging it into a Docker container for deployment.

Step One: Install Docker
First, you need to install Docker. You can download the installer for your operating system on the Docker official website and install it according to the instructions of the official documentation. Once the installation is complete, you can verify that Docker installed successfully by running the docker version command in a terminal or command prompt.

Step 2: Create a Spring Boot application
Next, we will create a simple Spring Boot application. Open your favorite Java integrated development environment (IDE) and create a new Spring Boot project. In the root directory of the project, create a class named HelloWorldController.java and add the following code:

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloWorldController {
    
    @GetMapping("/")
    public String helloWorld() {
        return "Hello, World!";
    }
}

This code creates a class named HelloWorldController RESTful controller that handles HTTP GET requests for the root path and returns the string Hello, World!.

Step Three: Build and Run the Spring Boot Application
After finishing writing the application code, we need to build and run the application. In a terminal or command prompt, navigate to the root directory of your project and run the following command:

./gradlew clean build
java -jar build/libs/your-app-name.jar

This will build the application using Gradle and package it as an executable JAR file. Then, you can visit http://localhost:8080 in your browser and you should be able to see the response of Hello, World!.

Step 4: Create Dockerfile
Now we will create a file named Dockerfile, which is used to define the build rules of the Docker container. Create a file named Dockerfile in the root directory of the project and add the following content to the file:

FROM adoptopenjdk:11-jdk-hotspot
VOLUME /tmp
EXPOSE 8080
ARG JAR_FILE=build/libs/*.jar
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

This Dockerfile uses a base image adoptopenjdk:11- jdk-hotspot, and defines the container’s volume, port, build parameters, and execution commands. Among them, ARG JAR_FILE=build/libs/*.jar is used to specify the JAR file path of the application.

Step 5: Build the Docker image
After completing the writing of the Dockerfile, we need to build the Docker image. In a terminal or command prompt, navigate to the root directory of your project and run the following command:

docker build -t your-image-name .

This will use the Dockerfile in the Docker build context and package it into a file called your- Image-name's image.

Step Six: Run the Docker Container
Finally, we will run the Docker container and deploy our Spring Boot application. In a terminal or command prompt, run the following command:

docker run -p 8080:8080 your-image-name

This will run the Docker container and map the local 8080 port to the container's 8080 port. Then, you can visit http://localhost:8080 in your browser and you should be able to see the response of Hello, World!.

Summary
Through this quick start guide, you have learned how to use Docker and Spring Boot to quickly develop and deploy containerized applications. This way of packaging Spring Boot applications into Docker containers enables fast, consistent, and reliable deployment, making your applications more flexible and portable.

I hope this article is helpful to you, and I wish you success in containerized application development with Docker and Spring Boot!

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