How to deploy SpringBoot project using Docker

The development of Docker technology provides a more convenient environment for the implementation of microservices. It is actually very simple to deploy Spring Boot using Docker. Let's learn it briefly in this article.

First, build a simple Spring Boot project, then add Docker support to the project, and finally deploy the project.

A simple Spring Boot project

In pom.xml, use Spring Boot 2.0 related dependencies

<parent>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-parent</artifactId>
 <version>2.0.0.RELEASE</version>
</parent>

Add web and test dependencies

<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>

Create a DockerController with an index() method that returns: Hello Docker!

@RestController
public class DockerController {
 
  @RequestMapping("/")
  public String index() {
    return "Hello Docker!";
  }
}

Startup Class

@SpringBootApplication
public class DockerApplication {
 
 public static void main(String[] args) {
 SpringApplication.run(DockerApplication.class, args);
 }
}

After adding, start the project. After successful startup, visit http://localhost:8080/ in the browser. The page returns: Hello Docker!, indicating that the Spring Boot project is configured normally.

Spring Boot project adds Docker support

Add the Docker image name in pom.xml-properties

<properties>
 <docker.image.prefix>springboot</docker.image.prefix>
</properties>

Add the Docker build plugin in plugins:

<build>
 <plugins>
 <plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
 </plugin>
 <!-- Docker maven plugin -->
 <plugin>
  <groupId>com.spotify</groupId>
  <artifactId>docker-maven-plugin</artifactId>
  <version>1.0.0</version>
  <configuration>
  <imageName>${docker.image.prefix}/${project.artifactId}</imageName>
  <dockerDirectory>src/main/docker</dockerDirectory>
  <resources>
   <resource>
   <targetPath>/</targetPath>
   <directory>${project.build.directory}</directory>
   <include>${project.build.finalName}.jar</include>
   </resource>
  </resources>
  </configuration>
 </plugin>
 <!-- Docker maven plugin -->
 </plugins>
</build>

Create a Dockerfile file in the directory src/main/docker. The Dockerfile file is used to explain how to build the image.

FROM openjdk:8-jdk-alpine
VOLUME /tmp
ADD spring-boot-docker-1.0.jar app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

This Dockerfile is very simple. It builds the JDK basic environment and adds the Spring Boot Jar to the image. Here is a brief explanation:

• FROM means using the Jdk8 environment as the base image. If the image is not local, it will be downloaded from DockerHub.
• VOLUME, VOLUME points to a /tmp directory. Since Spring Boot uses the built-in Tomcat container, Tomcat uses /tmp as the working directory by default. The effect of this command is: create a temporary file in the host's /var/lib/docker directory and link it to the /tmp directory in the container
• ADD, copy the file and rename it
• ENTRYPOINT, to shorten Tomcat startup time, add the java.security.egd system property to point to /dev/urandom as ENTRYPOINT

This completes adding Docker dependencies to the Spring Boot project.

Build a packaging environment

We need a Docker environment to package the Spring Boot project. It is troublesome to build a Docker environment on Windows, so I will take Centos 7 as an example.

Install Docker Environment

Install

yum install docker

After the installation is complete, use the following command to start the Docker service and set it to start at boot:

service docker start
chkconfig docker on
 
#LCTT Annotation: The old sysv syntax is used here. For example, the new systemd syntax supported in CentOS 7 is as follows:
systemctl start docker.service
systemctl enable docker.service

Using Docker China Accelerator

vi /etc/docker/daemon.json
 
#After adding:
{
  "registry-mirrors": ["https://registry.docker-cn.com"],
  "live-restore": true
}

Restart docker

systemctl restart docker

Enter docker version. If the version information is returned, the installation is successful.

Install JDK

yum -y install java-1.8.0-openjdk*

Configure environment variables Open vim /etc/profile and add the following content

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64
export PATH=$PATH:$JAVA_HOME/bin

After the modification is completed, make it effective

source /etc/profile

If the version information is returned when you enter java -version, the installation is successful.

Installing MAVEN

Download: http://mirrors.shu.edu.cn/apache/maven/maven-3/3.5.2/binaries/apache-maven-3.5.2-bin.tar.gz

## Unzip tar vxf apache-maven-3.5.2-bin.tar.gz
## Move mv apache-maven-3.5.2 /usr/local/maven3

Modify the environment variables and add the following lines to /etc/profile

MAVEN_HOME=/usr/local/maven3
export MAVEN_HOME
export PATH=${PATH}:${MAVEN_HOME}/bin

Remember to execute source /etc/profile to make the environment variables take effect.

Enter mvn -version and if the version information is returned, the installation is successful.

This completes the configuration of the entire build environment.

Deploy Spring Boot project using Docker

Copy the spring-boot-docker project to the server and enter the project path for packaging and testing.

#Packaging mvn package
#Start java -jar target/spring-boot-docker-1.0.jar

After seeing the Spring Boot startup log, it shows that there is no problem with the environment configuration. Next, we use DockerFile to build the image.

mvn package docker:build

The first build may be a bit slow, and the build is successful when you see the following:

...
Step 1: FROM openjdk:8-jdk-alpine
 ---> 224765a6bdbe
Step 2: VOLUME /tmp
 ---> Using cache
 ---> b4e86cc8654e
Step 3: ADD spring-boot-docker-1.0.jar app.jar
 ---> a20fe75963ab
Removing intermediate container 593ee5e1ea51
Step 4: ENTRYPOINT java -Djava.security.egd=file:/dev/./urandom -jar /app.jar
 ---> Running in 85d558a10cd4
 ---> 7102f08b5e95
Removing intermediate container 85d558a10cd4
Successfully built 7102f08b5e95
[INFO] Built springboot/spring-boot-docker
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 54.346 s
[INFO] Finished at: 2018-03-13T16:20:15+08:00
[INFO] Final Memory: 42M/182M
[INFO] ------------------------------------------------------------------------

Use the docker images command to view the built image:

docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
springboot/spring-boot-docker latest 99ce9468da74 6 seconds ago 117.5 MB

springboot/spring-boot-docker is the image we built. The next step is to run the image.

docker run -p 8080:8080 -t springboot/spring-boot-docker

After the startup is complete, we use docker ps to view the running image:

docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
049570da86a9 springboot/spring-boot-docker "java -Djava.security" 30 seconds ago Up 27 seconds 0.0.0.0:8080->8080/tcp determined_mahavira

You can see that the container we built is running. Visit the browser: http://192.168.0.x:8080/, and return

Hello Docker!

This shows that the Spring Boot project was successfully deployed using Docker!

Example code: https://github.com/ityouknow/spring-boot-examples

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