Implementation steps for Docker deployment of SpringBoot applications

Preface
Dockerfile

What is a Dockerfile?
Dockerfile Syntax

Packaging SpringBoot Project

Package the SpringBoot application into a jar locally

Prepare jar package and Dockerfile

Writing a Dockerfile

Use the tool to upload the jar and Dockerfile to the server

Build the image

View Mirror

Create and run the container
View the running image

View logs

Preface

When deploying a project, you may need to rely on node.js, Redis, RabbitMQ, MySQL, etc. The function libraries and dependencies required for the deployment of these services are different and may even conflict with each other. This brought great difficulties to the deployment. Docker has cleverly solved these problems. In order to solve the compatibility issues of dependencies, Docker uses two methods:

Package the application's Libs (function libraries), Deps (dependencies), and configurations together with the application
Run each application in an isolated container to avoid interference with each other.

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This article will explain how to use Docker to deploy the projects we usually develop with SpringBoot:

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Dockerfile

What is a Dockerfile?

Dockerfile is a text file used to build an image. The text content contains the instructions and instructions required to build the image.

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Dockerfile Syntax

When building a custom image, you do not need to copy and package each file one by one.

We only need to tell Docker the composition of our image, which BaseImages are needed, what files need to be copied, what dependencies need to be installed, and what the startup script is. In the future, Docker will help us build the image.

The file that describes the above information is the Dockerfile file.

Dockerfile is a text file that contains instructions that describe what operations to perform to build an image. Each instruction forms a layer.

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Packaging SpringBoot Project

Preparation Project:

Project Port

server.port=8080

Create a new index.html in the templates folder

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Docker deployment SpringBoot application</title>
</head>
<body>
<h1>Docker deployment of SpringBoot applications</h1>
<img src="/static/img/2.jpg" alt="" width="100%">
</body>
</html>

Define the homepage Controller and jump to the index

@Controller
public class indexController {

    @RequestMapping("/")
    public String index(){
        return "index";
    }
}

Preview the effect locally:

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Package the SpringBoot application into a jar locally

Prepare the maven-compiler-plugin plugin

<build>
	<!--Compiled and packaged file name-->
	<finalName>app</finalName>
	<plugins>
		<plugin>
			<!--GAV coordinates (G organization id, A project id, V version number)-->
			<groupId>org.apache.maven.plugins</groupId>
			<artifactId>maven-compiler-plugin</artifactId>
			<version>3.8.1</version>
			<!--Configuration:
		    Generally speaking, target and source are consistent, but sometimes in order to allow the program to run in other versions of JDK (for lower version target JDK, the source code cannot use syntax that is not supported by the lower version JDK), there will be a situation where target is different from source -->
			<configuration>
				<!--JDK version used by the source code-->
				<source>1.8</source>
				<!-- The compiled version of the target class file to be generated-->
				<target>1.8</target>
				<!-- Character set encoding to prevent Chinese garbled characters -->
				<encoding>UTF-8</encoding>
			</configuration>
		</plugin>
	</plugins>
</build>

Maven is a project management tool. If you don't tell it what JDK version to use to compile the code, it will use the default JDK version of the compilation plug-in maven-compiler-plugin to handle it. This will easily lead to version mismatch problems, which may cause compilation failure. For example, if the code uses new features of Java 8, such as functional programming, but Maven uses Java 7 when compiling, then it is completely impossible to compile this code into a .class file. To avoid this situation, when building a Maven project, my first step is to configure the Maven-compiler-plugin plug-in, specifying the JDK version of the project source code, the compiled JDK version, and the encoding method.

Then execute clean, and finally execute package to package the project

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The BUILD SUCCESS message indicates that the package was successfully completed.

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After the packaging is successful, the target folder will appear, and the jar package just packaged will be in the directory

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Prepare jar package and Dockerfile

Copy the jar to the desktop or a custom location, and create and write the Dockerfile file locally (注：名字必須為Dockerfile,去掉后綴名）

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Writing a Dockerfile

Dockerfile instructions

FROM java:8-alpine
COPY ./app.jar /tmp/app.jar
ENTRYPOINT java -jar /tmp/app.jar

Dockerfile Description

FROM java:8-alpine:

Build an image based on java8. By default, building a java image requires installing and configuring environment variables. The java:8-alpine image has already completed all the previous steps for us.

COPY ./app.jar /tmp/app.jar

Copy the jar package

ENTRYPOINT java -jar /tmp/app.jar

Entry Command

Use the tool to upload the jar and Dockerfile to the server

The upload location depends on the individual. I store it in: /tmp/docker

cd tmp
mkdir docker

Select Upload File

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Upload to the /tmp/docker directory

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Build the image

Enter the directory where you uploaded the file: cd /tmp/docker , enter ls to view the file

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Enter the command to build the image

docker build -t test:1.0 .

格式：docker build -t 鏡像名稱:版本號Dockerfile所在目錄路徑

Command Explanation:

build : Docker's secondary command

Build the image

-t

- Name: General image name format: name: version number ( test:1.0 )

.

The directory where the Dockerfile is located. Since we have entered the directory where the Dockerfile is located, . represents the current directory.

You can see that when building the image, it will be executed in three steps according to the three commands we wrote in Dockerfile

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View Mirror

View the image command in Docker:

docker images

You can see our custom image test

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Create and run the container

Run the Docker image command:

docker run --name springboot -p 8080:8080 -d test:1.0

Command Explanation:

docker run ： docker secondary command

Create and run the container

--name

Define the container name, followed by the container name ( springboot )

-p port mapping

The port on the left is the Linux port, and the port on the right is the container port number
Map the Linux port to the container port number, so that accessing the Linux port is equivalent to accessing the container port number

-d

Run the container in the background, otherwise the container will stop running after exiting

test:1.0 –>image name

Select version 1.0 of the custom image test to create a container

The container was created and run successfully!

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View the running image

Running image command

docker ps

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Browser accesses the server's port 8080

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Mobile access:

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View logs

View container log command

docker logs -f springboot

illustrate:

View container logs but they are not updated in real time. You need to run again if you want to view new logs

docker logs + container name

Real-time update log

docker logs -f + container name

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The Docker deployment SpringBoot application tutorial is over!

This is the end of this article about Docker deployment of SpringBoot applications. For more relevant content about Docker deployment of SpringBoot applications, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope you will support 123WORDPRESS.COM in the future!

You may also be interested in:

Detailed process of SpringBoot integrating Docker
Detailed process of integrating docker with idea to quickly deploy springboot applications
Introduction to Docker Quick Deployment of SpringBoot Project

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