Spring Boot 4 Microservices & REST APIs · 课时

将 Spring Boot 应用容器化

创建 Dockerfile，将 Spring Boot 应用打包为轻量且可移植的容器。

将 Spring Boot 应用容器化 是 CoddyKit 上的免费 Spring Boot 4 Microservices & REST APIs 课时。这是第 1 节课，共 3 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Spring Boot 4 Microservices & REST APIs 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Spring Boot 4 Microservices & REST APIs 课程共包含 3 节课。

本课时的部分内容尚未翻译，以英文显示。

Why Dockerize Spring Boot?

Welcome to containerizing Spring Boot apps! Docker helps package your application into a standardized unit called a container.

Why is this great for Spring Boot?

Portability: Run your app consistently anywhere Docker runs.
Isolation: Your app and its dependencies are bundled together, avoiding conflicts.
Consistency: The environment is the same from development to production.

Docker Fundamentals for Apps

Before we dive in, let's quickly define key Docker terms:

Image: A lightweight, standalone, executable package that includes everything needed to run a piece of software, including the code, a runtime, libraries, environment variables, and config files. Think of it as a blueprint.
Container: A runnable instance of an image. You can create, start, stop, move, or delete a container. It's the actual running application.
Dockerfile: A text file that contains all the commands, in order, to build a given image.

Our Sample Spring Boot App

Let's imagine we have a simple Spring Boot application. When we build it, it typically produces a single executable JAR file (e.g., my-app.jar).

Here's a basic Spring Boot application structure:

package com.coddykit.docker;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DockerApp {

  public static void main(String[] args) {
    SpringApplication.run(DockerApp.class, args);
    // This will print to the container's standard output
    System.out.println("Spring Boot app started inside Docker!");
  }
}

Introducing the Dockerfile

A Dockerfile is a script of instructions that Docker uses to build an image. It's like a recipe for creating your container environment.

We'll create a file named Dockerfile (no extension) in the root directory of our Spring Boot project. Each line in the Dockerfile is an instruction.

Choosing a Base Image (FROM)

Every Dockerfile starts with the FROM instruction. This specifies the base image your application will build upon. For Java applications, a common choice is an OpenJDK image.

openjdk:17-jdk-slim provides a Java 17 Development Kit (JDK) in a slim, smaller image, which is great for production.

FROM openjdk:17-jdk-slim

Copying Your Application (COPY)

Next, we need to get our compiled Spring Boot JAR file into the Docker image. The COPY instruction does exactly that.

Assuming your built JAR is in target/my-app.jar, we copy it into the image's root directory and rename it to app.jar for simplicity.

COPY target/my-app.jar app.jar

Exposing Ports (EXPOSE)

Spring Boot applications typically run on a specific port, often 8080. The EXPOSE instruction informs Docker that the container listens on the specified network ports at runtime.

While EXPOSE doesn't actually publish the port, it serves as documentation and helps with port mapping when running the container.

EXPOSE 8080

Defining the Entrypoint (ENTRYPOINT)

The ENTRYPOINT instruction configures a container that will run as an executable. This is how we tell Docker to start our Spring Boot application when the container launches.

We use the java -jar app.jar command to execute our application's JAR file.

ENTRYPOINT ["java", "-jar", "app.jar"]

Putting It All Together: Dockerfile

Here's what our complete Dockerfile looks like. You would place this file in the root of your Spring Boot project.

FROM openjdk:17-jdk-slim
VOLUME /tmp
COPY target/docker-app-0.0.1-SNAPSHOT.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "/app.jar"]

Note: The JAR name might vary based on your project. VOLUME /tmp is often added to support Spring Boot's embedded Tomcat.

Building Your Docker Image

Once your Dockerfile is ready and your Spring Boot application is compiled (e.g., using mvn package), you can build the Docker image.

Navigate to your project's root directory in the terminal and run:

docker build -t my-spring-app .

This command:

docker build: Initiates the image build process.
-t my-spring-app: Tags the image with a name (my-spring-app).
.: Specifies the build context (the current directory, where the Dockerfile is located).

Dockerfile Instruction Check

Which Dockerfile instruction is used to define the command that runs when a container starts from an image?

Recap: Dockerizing Your App

You've successfully learned the basics of Dockerizing a Spring Boot application!

We understood the role of Dockerfiles, images, and containers.
We explored key Dockerfile instructions: FROM, COPY, EXPOSE, and ENTRYPOINT.
You now know how to bundle your Spring Boot JAR into a portable Docker image.

This sets the stage for running your applications consistently in any Docker environment!

常见问题解答

「将 Spring Boot 应用容器化」课时是免费的吗？

是的 — 「将 Spring Boot 应用容器化」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Spring Boot 4 Microservices & REST APIs 课程的其余内容，请升级到 CoddyKit PRO。 Spring Boot 4 Microservices & REST APIs 课程共包含 3 节课。

「将 Spring Boot 应用容器化」这节课中我会学到什么？

创建 Dockerfile，将 Spring Boot 应用打包为轻量且可移植的容器。你通过在浏览器中直接运行的动手代码来练习 Spring Boot 4 Microservices & REST APIs，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Spring Boot 4 Microservices & REST APIs 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Spring Boot 4 Microservices & REST APIs 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 1 节课，共 3 节。

「将 Spring Boot 应用容器化」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Spring Boot 4 Microservices & REST APIs 课中编写并运行代码吗？

能。每节 Spring Boot 4 Microservices & REST APIs 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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