Spring Boot Integration with Docker

Cloud Technologies
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Spring Boot Integration with Docker

What is Docker?

Docker is an open-source engine that allows developers to create lightweight, portable, and self-contained containers for any application. With Docker, developers can test and deploy containers in a variety of environments, including virtual machines, bare metal, OpenStack clusters, and more.

Docker Application Scenarios

  1. Automated Packaging and Publishing Web Applications: Docker can automate the packaging and publishing of web applications, making it easier to deploy and manage applications.
  2. Automated Testing and Continuous Integration: Docker can automate testing and continuous integration, ensuring that applications are thoroughly tested and validated before deployment.
  3. Deployment and Tuning of Database or Other Back-Office Applications: Docker can deploy and tune database or other back-office applications in a service-oriented environment.
  4. Recompiling or Extending an Existing OpenShift or Cloud Foundry PaaS Platform: Docker can recompile or extend an existing OpenShift or Cloud Foundry PaaS platform to build a custom environment.

Integration of Docker with Spring Boot

To integrate Docker with Spring Boot, we need to create a Spring Boot project and then containerize it using Docker.

Create a Spring Boot Project

Let’s create a Spring Boot project called springboot-docker. We will create a Start class with a main method that runs the Spring Boot application.

package com.gf;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class SpringbootDockerApplication {

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

    @GetMapping("/hi/{name}")
    public String hi(@PathVariable(value = "name") String name) {
        return "hi," + name;
    }
}

Containerize the Spring Boot Application using Docker

To containerize the Spring Boot application using Docker, we need to create a Dockerfile in the src/main/resources/docker directory. The Dockerfile will specify the base image, volume, add the Spring Boot application JAR file, and set the entry point.

FROM frolvlad/alpine-oraclejdk8:slim
VOLUME /tmp
ADD springboot-docker-0.0.1-SNAPSHOT.jar app.jar
RUN sh -c 'touch /app.jar'
ENV JAVA_OPTS=""
ENTRYPOINT ["sh", "-c", "java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar"]

Build the Docker Image using Maven

To build the Docker image, we need to add the docker-maven-plugin to the pom.xml file. The pom.xml file will specify the project metadata, dependencies, and plugins.

<?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>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.gf</groupId>
    <artifactId>springboot-docker</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>springboot-docker</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <docker.image.prefix>gf</docker.image.prefix>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>com.spotify</groupId>
                <artifactId>docker-maven-plugin</artifactId>
                <version>1.2.0</version>
                <configuration>
                    <imageName>${docker.image.prefix}/${project.artifactId}</imageName>
                    <dockerDirectory>src/main/resources/docker</dockerDirectory>
                    <resources>
                        <resource>
                            <targetPath>/</targetPath>
                            <directory>${project.build.directory}</directory>
                            <include>${project.build.finalName}.jar</include>
                        </resource>
                    </resources>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Build the Docker Image

To build the Docker image, we need to run the following commands:

mvn clean
mvn package docker:build

View the Docker Image

To view the Docker image, we need to run the following command:

docker images

Run the Docker Container

To run the Docker container, we need to run the following command:

docker run -p 8080:8080 -t c2dba352c3c1

We can now access the service by navigating to http://localhost:8080/hi/John.