docker-java

Docker Java Workshop

In this workshop, we will containerize a simple Hello World http app. The application runs as a single executable jar file. Details on building and running the application can be found below.

Exercise

For this exercise, our goal is to move the Hello World app to a container. We will

• create a Dockerfile
• build an image
• execute the container

Next, we'll explore docker-compose and run a caching container that our application can interact with.

• create a docker-compose.yml for the application
• add the redis image to our docker-compose.yml
• set environment variable for the app to talk to redis
• use docker-compose to run multiple containers (1 app, 1 redis)

Creating the Dockerfile

First, we need to create a Dockerfile for our app.

• The FROM image should be the java 8 openjdk
• All relevant files need to be added to the image
• Document published ports (default http for the app is 4567)

Building the image

• Specify a name for your image

Running a container

• Set environment variables
• Don't forget to map ports

Hello World API

The hello world application presents a simple http API with two endpoints.

• GET /hello will return a hello world message
• GET /cache will validate redis connectivity

Building the application

To build the application, execute the build task using one of the following commands in the root of the repository:

Windows:

gradlew.bat build

Mac and Linux:

./gradlew build

The build will produce two jar files in the build/libs/ directory.

Running the application

To run the application, execute the shadow jar file (More information on shadow):

java -jar build/libs/shadow.jar