[JAVA] Spring Boot starting with Docker

When I thought about developing a web application with Java Spring Boot, I decided to build a development environment using Docker while also studying Docker.

Operating environment

• OS: Mac OS X 10.12.6 x86_64 (macOS Sierra)
• Gradle: 3.5.1
• JVM: 1.8.0_152-ea
• Docker for Mac: Version 17.09.0-ce-mac35

Spring Boot implementation

Download template

First, create a Spring Boot template with Spring Initializr.

1. Select Gradle Project
2. Change Group to hello (default is okay)
3. Change ʻArtifact` to hello (default is okay)
4. Add Web to Dependencies

Then download the template with Generate Project.

Change build.gradle

Use Gradle to build your app and manage dependent libraries. The build script build.gradle is included in the template downloaded above, so change it as follows.

buildscript {
    ext {
        springBootVersion = '1.5.7.RELEASE'
    }
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
    }
}

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'idea'
apply plugin: 'org.springframework.boot'

jar {
    baseName = 'hello-world'
    version = '0.1.0'
}

sourceCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    compile('org.springframework.boot:spring-boot-starter-web')
    testCompile('org.springframework.boot:spring-boot-starter-test')
}

If you use IntelliJ IDEA as the editor, it will install the necessary libraries without permission. If you are not using it, run gradlew clean build.

Changes to HelloApplication.java

Change src / main / java / hello / hello / HelloApplication.java in the downloaded template as follows.

package hello.hello;

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

@SpringBootApplication
@RestController
public class HelloApplication {

    @RequestMapping("/")
    public String home() {
        return "Hello World from Docker";
    }

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

}

Operation check

Let's check the operation here for the time being. The jar file should be created under build / libs. Execute the following command and check if it outputs Hello World from Docker.

$ ./gradlew build && java -jar build/libs/hello-world-0.1.0.jar
$ curl http://localhost:8080

Environment construction with Docker

Creating a Dockerfile

At this point, set up the environment with Docker. If Docker is not installed, download it from here and install it. Place Dockerfile in the root directory and describe the contents as follows.

FROM openjdk:jdk-alpine
VOLUME /tmp
RUN mkdir /app
WORKDIR /app
ENV JAVA_OPTS=""
ENTRYPOINT [ "sh", "-c", "java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar build/libs/hello-world-0.1.0.jar" ]

docker-compose settings

In the future, I think that there will be cases where I want to manage the container for applications and the container for DB separately, so I will use docker-compose. Place docker-compose.yml in the root directory and describe the contents as follows.

version: '2'
services:
    app:
        build: .
        image: tiqwab/boot:0.0.1
        ports:
            - "8080:8080"
        volumes:
            - .:/app

Build docker image & start container

Now that you're ready, build the docker image with the following command and start the container.

$ docker-compose up --build

In this state, try accessing http: // localhost: 8080 /. You should see Hello World from Docker.

From now on, you can start the container with the following command.

#Start-up
$ docker-compose up -d

#Stop
$ docker-compose stop

With the above, you can easily build a Spring Boot development environment using Docker.

reference

-Spring Boot with Docker development environment

• Getting Started · Spring Boot with Docker