Docker Hello World

Steps for building the image and running the container

1. Build a Jar
   target/docker-hello-world.jar
2. Setup the Prerequisites for Running the JAR
   docker run -dit openjdk:11
3. Copy the jar
   

docker container cp target/docker-hello-world.jar <<container-name>>:/tmp
docker container commit --change='CMD ["java","-jar","/tmp/docker-hello-world.jar"]' <<container-name>> docker-hello-world:latest

4. Run the jar
   docker run -p 8080:8080 docker-hello-world:latest     
   Detached mode
        docker run -p 8080:8080 -d docker-hello-world:latest

Running the Application

• http://localhost:8080/hello-world

Hello World

• http://localhost:8080/hello-world-bean

{"message":"Hello World"}

• http://localhost:8080/hello-world/path-variable/in28minutes

{"message":"Hello World, in28minutes"}

Automate the process

############## Basic

1. Add a new file at project level: "Dockerfile"
2. Add the following to the file

 FROM openjdk:11
 EXPOSE 8080
 ADD target/docker-hello-world.jar docker-hello-world.jar
 ENTRYPOINT ["sh", "-c", "java -jar /docker-hello-world.jar"]

3. Build the Docker Image using command
   docker build -t docker-hello-world:wrkspc .
4. Run the Docker Container using
   docker run -p 8080:8080 -d docker-hello-world:wrkspc

Create images with MAVEN

With Spring Boot 2.3.0 we can create images while running maven build      - mvn spring-boot:build-image

To make proper usage of the CACHE functionality of Docker

######## we need to create images not from the fat jar but the class files and dependencies ############Follow below steps to achieve the above

1. Add a plugin for this type of build

FROM openjdk:11
ARG DEPENDENCY=target/dependency
COPY ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY ${DEPENDENCY}/META-INF /app/META-INF
COPY ${DEPENDENCY}/BOOT-INF/classes /app
ENTRYPOINT ["java","-cp","app:app/lib/*","com.tanmay.docker.dockerhelloworld.DockerHelloWorldApplication"]

2. Add the following dependency in pom.xml

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>mave    n-dependency-plugin</artifactId>
    <executions>
        <execution>
            <id>unpack</id>
            <phase>package</phase>
            <goals>
                <goal>unpack</goal>
            </goals>
            <configuration>
                <artifactItems>
                    <artifactItem>
                        <groupId>${project.groupId}</groupId>
                        <artifactId>${project.artifactId}</artifactId>
                        <version>${project.version}</version>
                    </artifactItem>
                </artifactItems>
            </configuration>
        </execution>
    </executions>
</plugin>

3. Run maven command for image creation mvn spring-boot:build-image

########################### PLUGINS

JIB plugin

1. Remove the Dockerfile
2. Add the below maven dependency

<plugin>
	<groupId>com.google.cloud.tools</groupId>
	<artifactId>jib-maven-plugin</artifactId>
	<version>1.6.1</version>
	<configuration>
		<container>
			<creationTime>USE_CURRENT_TIMESTAMP</creationTime>
		</container>
	</configuration>
	<executions>
		<execution>
			<phase>package</phase>
			<goals>
				<goal>dockerBuild</goal>
			</goals>
		</execution>
	</executions>
</plugin>

    
Extra Configurations which makes it similar to Dockerfile     

<configuration>
	<from>
		<image>openjdk:alpine</image>
	</from>
	<to>
		<image>in28min/${project.name}</image>
		<tags>
			<tag>${project.version}</tag>
			<tag>latest</tag>
		</tags>
	</to>
	<container>
		<jvmFlags>
			<jvmFlag>-Xms512m</jvmFlag>
		</jvmFlags>
		<mainClass>com.in28minutes.rest.webservices.restfulwebservices.RestfulWebServicesApplication</mainClass>
		<ports>
			<port>8100</port>
		</ports>
	</container>
</configuration>