How do you configure a Maven/SpringBoot Project's pom.xml for docker? - maven

Question

I am attempting to dockerize my SpringMVC application via Maven. My intent is to have an image that I can then proceed to expose and display via my web browser.
Unfortunately, in following this guide, I appear to still lack a critical piece of understanding concerning the pom.xml edits I must make to achieve this, and the Dockerfile.
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Here is the Dockerfile:
FROM openjdk:8-jdk-alpine
VOLUME /tmp
ARG JAR_FILE
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]
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Here is the source code's pom.xml in its latest revision.
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Here is my latest attempt at revision, in following the example pom.xml of the SpringIO guide I referenced above (dependencies section not included).
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.5.RELEASE</version>
<relativePath /> <!-- lookup parent from repository -->
</parent>
<groupId>com.davidonus</groupId>
<artifactId>davidonusSpringDemo1</artifactId>
<version>0.0.1-SNAPSHOT</version>
<!-- tag::packaging[] -->
<packaging>jar</packaging>
<name>davidonusSpringDemo1</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<!-- tag::docker[] -->
<docker.image.prefix>springio</docker.image.prefix>
</properties>
<profiles>
<profile>
<id>DavidSpringTime</id>
</profile>
</profiles>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<!-- tag::plugin[] -->
<plugin>
<groupId>com.spotify</groupId>
<artifactId>dockerfile-maven-plugin</artifactId>
<version>1.4.9</version>
<configuration>
<repository>${docker.image.prefix}/${project.artifactId}</repository>
</configuration>
</plugin>
<!-- end::plugin[] -->
<!-- tag::unpack[] -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>unpack</id>
<phase>package</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>${project.groupId}</groupId>
<artifactId>${project.artifactId}</artifactId>
<version>${project.version}</version>
</artifactItem>
</artifactItems>
</configuration>
</execution>
</executions>
</plugin>
<!-- end::unpack[] -->
</plugins>
</build>
Here are my present results, using the command mvn install build:docker
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 12.050 s
[INFO] Finished at: 2019-06-15T13:24:01-04:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-dependency-plugin:3.1.1:unpack (unpack) on project davidonusSpringDemo1: Unable to update Marker timestamp: /home/david/Desktop/DevOps2019/springBoot/teluskoSpringBoot/target/dependency-maven-plugin-markers/com.davidonus-davidonusSpringDemo1-jar-0.0.1-SNAPSHOT.marker: Unable to update last modified timestamp on marker file /home/david/Desktop/DevOps2019/springBoot/teluskoSpringBoot/target/dependency-maven-plugin-markers/com.davidonus-davidonusSpringDemo1-jar-0.0.1-SNAPSHOT.marker -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException
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In summary, given my original pom.xml, what changes would you implement to make my SpringBoot + Maven project deployable as a docker image and container?
Furthermore, are there adaptions to my Dockerfile that you'd make? Your consultation is appreciated. Thank you.

Answer 1

If you have your springboot code ready with pom.xml. Then follow below steps to containerize your application.
git clone https://github.com/dnmorris7/teluskoSpringBoot (I'm cloning your springboot code)
git checkout module5 (checked out module5 branch)
Created Dockerfile in your git codebase with following contents:
FROM maven:3.6-jdk-8-slim AS build
COPY . /usr/src/app/
WORKDIR /usr/src/app/
RUN mvn -f /usr/src/app/pom.xml clean package
FROM java:8-alpine
WORKDIR /
COPY --from=build /usr/src/app/target/*.jar /app.jar
CMD java -jar app.jar
NOTE: I'm using docker multi-stage build where in first stsage maven builds the jar and in the second stage we copy that jar in java image.
Now build your docker image docker build -t appimage:v1 .
Run your docker container docker run -it -d -p 9090:9090 appimage:v1
Hit the api to check if its working fine.
$ curl localhost:9090/home
{"timestamp":"2019-06-16T05:34:26.655+0000","status":404,"error":"Not Found","message":"/pages/home.jsp","path":"/home"}
Please hit the correct base url, I tried with /home
NOTE: If you want to provide your own custom application.properties then change the java -jar command in Dockerfile to CMD java -jar app.jar --spring.config.additional-location=application.properties and change the docker run command to docker run -it -d -v application.properties:/application.properties -p 9090:9090 appimage:v1 where application.properties is the one which you provide from outside.

Answer 2

I think not much is missing. Or even better there may be even too many things.
First, you need to tell the docker maven plugin to run. The maven lifecycle defines which plugins run at what phase. So all other plugins need an execution configuration somewhere (in a parent pom or in yours). Second, there is no need to unpack the created jar file. Spring Boot will create an executable jar file automatically. You only need to tell the docker maven plugin about it (where it is created)
This would be the Dockerfile:
FROM openjdk:8-jdk-alpine
VOLUME /tmp
ARG JAR_FILE
ADD target/${JAR_FILE} /usr/share/myapp.jar
ENTRYPOINT ["java","-jar","/usr/share/myapp.jar"]
And this your pom:
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.springframework</groupId>
<artifactId>gs-spring-boot-docker</artifactId>
<version>0.1.0</version>
<packaging>jar</packaging>
<name>Spring Boot Docker</name>
<description>Getting started with Spring Boot and Docker</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.4.RELEASE</version>
<relativePath />
</parent>
<properties>
<docker.image.prefix>springio</docker.image.prefix>
<java.version>1.8</java.version>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<!-- tag::plugin[] -->
<plugin>
<groupId>com.spotify</groupId>
<artifactId>dockerfile-maven-plugin</artifactId>
<version>1.4.9</version>
<executions>
<execution>
<id>default</id>
<goals>
<goal>build</goal>
</goals>
</execution>
</executions>
<configuration>
<repository>${docker.image.prefix}/${project.artifactId}</repository>
<buildArgs>
<JAR_FILE>${project.build.finalName}.jar</JAR_FILE>
</buildArgs>
</configuration>
</plugin>
<!-- end::plugin[] -->
</plugins>
</build>
<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>
</project>
The unpack goal of the dependency plugin can be removed. This way the jar is added into the image and run directly. Hope it works!