Docker is a tool that can greatly simplify the process of developing and deploying Spring Boot applications. In this post, we'll take a look at how to use Docker to develop and deploy a Spring Boot application.
Developing a Spring Boot application with Docker is very simple. All you need is a text editor and a Dockerfile.
A Dockerfile is a text file that contains all the commands necessary to build a Docker image. A Docker image is a file that contains all the necessary files and dependencies for an application to run.
To create a Dockerfile, create a new file called Dockerfile
in the root directory of your project. Then, add the following lines to the file:
FROM java:8
ADD . /app
WORKDIR /app
RUN ./gradlew build
EXPOSE 8080
CMD ["java", "-jar", "build/libs/spring-boot-app-0.0.1-SNAPSHOT.jar"]
The first line, FROM java:8
, tells Docker to use the java:8
Docker image as the base image for our application. The java:8
Docker image contains all the necessary files and dependencies for a Java 8 application.
The second line, ADD . /app
, tells Docker to add all the files in the current directory (./
) to the /app
directory in the Docker image.
The third line, WORKDIR /app
, tells Docker to use the /app
directory as the working directory for our application.
The fourth line, RUN ./gradlew build
, tells Docker to run the ./gradlew build
command to build our application. This command will compile our code and create a .jar
file in the build/libs
directory.
The fifth line, EXPOSE 8080
, tells Docker to expose port 8080
for our application.
The sixth and final line, CMD ["java", "-jar", "build/libs/spring-boot-app-0.0.1-SNAPSHOT.jar"]
, tells Docker to run the java
command with the -jar
option and the spring-boot-app-0.0.1-SNAPSHOT.jar
file as arguments. This will start our application on port 8080
.
Now that we have a Dockerfile, we can build a Docker image for our application. To do this, open a terminal and navigate to the root directory of your project. Then, run the following command:
$ docker build -t spring-boot-app .
This command will build a Docker image for our application and tag it with the spring-boot-app
name.
Once the image is built, we can run it using the following command:
$ docker run -p 8080:8080 spring-boot-app
This command will start a Docker container for our image and map port 8080
on the host machine to port 8080
on the container.
Now, we can access our application at http://localhost:8080
.
Deploying a Spring Boot application with Docker is just as simple as developing one. All we need is a Dockerfile and a docker-compose.yml file.
A docker-compose.yml file is a YAML file that contains all the necessary configuration for docker-compose, a tool that can be used to manage multi-container applications.
To create a docker-compose.yml file, create a new file called docker-compose.yml
in the root directory of your project. Then, add the following lines to the file:
version: '2'
services:
app:
build: .
ports:
- "8080:8080"
The first line, version: '2'
, tells docker-compose to use version 2 of the docker-compose file format.
The second line, services:
, tells docker-compose that we are going to define a service. A service is a container that is part of a multi-container application.
The third line, app:
, is the name of our service.
The fourth line, build: .
, tells docker-compose to build our service using the Dockerfile
in the current directory (./
).
The fifth and final line, ports: - "8080:8080"
, tells docker-compose to map port 8080
on the host machine to port 8080
on the container.
Now that we have a docker-compose.yml file, we can deploy our application using the following command:
$ docker-compose up
This command will start our application on port 8080
.
In this post, we've seen how to use Docker to develop and deploy a Spring Boot application. Docker can greatly simplify the process of developing and deploying Spring Boot applications.