This post documents the steps I performed to containerize my REST application built with Spring Boot.
This uses the following tools
- Spring Tool Suite 4
- Maven – STS inbuilt
- Open JDK (Built by Azul)
- Docker
Step 1: Build your spring boot application using Maven:
This will build the file and jar file will be copied to the target folder of your project folder.
[code language=”text”]
[INFO] — maven-jar-plugin:3.1.2:jar (default-jar) @ messenger —
[INFO] Building jar: D:\Pandian\Documents\workspace_hamsa\messenger\target\messenger-0.0.1-SNAPSHOT.jar
[INFO]
[INFO] — spring-boot-maven-plugin:2.1.8.RELEASE:repackage (repackage) @ messenger —
[INFO] Replacing main artifact with repackaged archive
[INFO]
[INFO] — maven-install-plugin:2.5.2:install (default-install) @ messenger —
[INFO] Installing D:\Pandian\Documents\workspace_hamsa\messenger\target\messenger-0.0.1-SNAPSHOT.jar to C:\Users\barat\.m2\repository\org\grassfield\messenger\0.0.1-SNAPSHOT\messenger-0.0.1-SNAPSHOT.jar
[INFO] Installing D:\Pandian\Documents\workspace_hamsa\messenger\pom.xml to C:\Users\barat\.m2\repository\org\grassfield\messenger\0.0.1-SNAPSHOT\messenger-0.0.1-SNAPSHOT.pom
[INFO] ————————————————————————
[INFO] BUILD SUCCESS
[INFO] ————————————————————————
[INFO] Total time: 13.659 s
[INFO] Finished at: 2019-10-12T08:57:43+08:00
[INFO] ————————————————————————
[/code]
You may see above. The jar file messenger-0.0.1-SNAPSHOT.jar is created in the target folder.
Step 2: Create Dockerfile
We start building our own container now. We need to define the docker configuration in a Dockerfile. It will be placed in the root of project folder.
Following is the Docker file for this project.
[code language=”shell”]
#this uses alpine base image with openjdk 8
FROM openjdk:8-jdk-alpine
#Maintainer contact details
MAINTAINER Murugapandian Ramaiah
#where to persist the data generated by the container.
VOLUME /tmp
#which port of this container is to be exposed outside
EXPOSE 8080
#specify the SpringBoot bulky jar
ARG JAR_FILE=target/messenger-0.0.1-SNAPSHOT.jar
ADD ${JAR_FILE} messenger.jar
#specify how to execute the application
ENTRYPOINT [“java”,”-Djava.security.egd=file:/dev/./urandom”, “-jar”, “/messenger.jar”]
[/code]
Step 3: Build the container image
SSH the project folder to the /tmp partition of docker host Execute the following command.
[code language=”shell”]
$ cd /tmp/messenger
$ docker build -t messenger .
Step 1/7 : FROM openjdk:8-jdk-alpine
—> a3562aa0b991
Step 2/7 : MAINTAINER Murugapandian Ramaiah
—> Using cache
—> 4bb0470845c7
Step 3/7 : VOLUME /tmp
—> Using cache
—> 232d70e90d54
Step 4/7 : EXPOSE 8080
—> Using cache
—> 0a1d2e61d4a4
Step 5/7 : ARG JAR_FILE=target/messenger-0.0.1-SNAPSHOT.jar
—> Using cache
—> f179766aa87f
Step 6/7 : ADD ${JAR_FILE} messenger.jar
—> bc76f586ac0b
Step 7/7 : ENTRYPOINT [“java”,”-Djava.security.egd=file:/dev/./urandom”, “-jar”, “/messenger.jar”]
—> Running in 0646cdbee037
Removing intermediate container 0646cdbee037
—> 574eb9b9004b
Successfully built 574eb9b9004b
Successfully tagged messenger:latest
[/code]
The container image is created
[code language=”shell”]
$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
messenger latest 574eb9b9004b 23 minutes ago 123MB
openjdk 8-jdk-alpine a3562aa0b991 5 months ago 105MB
pandian/centos_ssh latest 7f019be4424c 14 months ago 294MB
centos latest 5182e96772bf 14 months ago 200MB
ubuntu latest 735f80812f90 14 months ago 83.5MB
hello-world latest 2cb0d9787c4d 15 months ago 1.85kB
[/code]
messenger is added.
Step 4: run the container.
[code language=”shell”]
$ docker run -p 6666:8080 messenger
. ____ _ __ _ _
/\\ / ___’_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | ‘_ | ‘_| | ‘_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
‘ |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.8.RELEASE)
2019-10-12 07:11:42.372 INFO 1 — [ main] org.grassfield.msg.MessengerApplication : Starting MessengerApplication v0.0.1-SNAPSHOT on 0f9f70c91b73 with PID 1 (/messenger.jar started by root in /)
2019-10-12 07:11:42.375 INFO 1 — [ main] org.grassfield.msg.MessengerApplication : No active profile set, falling back to default profiles: default
2019-10-12 07:11:43.394 INFO 1 — [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2019-10-12 07:11:43.430 INFO 1 — [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2019-10-12 07:11:43.431 INFO 1 — [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.24]
2019-10-12 07:11:43.530 INFO 1 — [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2019-10-12 07:11:43.530 INFO 1 — [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 1118 ms
2019-10-12 07:11:43.758 INFO 1 — [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService ‘applicationTaskExecutor’
2019-10-12 07:11:44.005 INFO 1 — [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ”
2019-10-12 07:11:44.008 INFO 1 — [ main] org.grassfield.msg.MessengerApplication : Started MessengerApplication in 2.072 seconds (JVM running for 2.438)
[/code]
I endorse this post by Rajeev – https://www.callicoder.com/spring-boot-docker-example/
