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2020/12/12

String Boot Jib Maven build docker image

使用GoogleContainerTools下的Jib maven plugin build Spring Boot docker image。

原本建置Spring Boot應用程式的docker image的步驟如下：

  1. build Spring Boot jar
  2. 撰寫Dockerfile
  3. 執行docker build

例如「Docker build Spring Boot docker image」這篇就是依以上步驟來建置docker image。


除了以上還可使用Google的Jib maven plugin來簡化以上步驟。Jib build的docker image若push到docker registry甚至不需要安裝Docker。

下圖是原本Docker build的過程。


+---------+     +---------+           +-----------------------------------------------+
| Project |---->|   JAR   |-------+   |   Docker Daemon                               |
+---------+     +---------+       |   | +---------------+  build  +-----------------+ |     +------------------+
                                  +---->| Build context |-------->| Container Image |------>| Container Image  |
                +------------+    |   | +---------------+         | (docker cache)  | |     | (registry)       |
                | Dockerfile |----+   |                           +-----------------+ |     +------------------+
                +------------+        +-----------------------------------------------+

下圖則是用Jib build的過程。

+---------+       Jib      +------------------+
| Project |--------------->| Container Image  |
+---------+                | (registry)       |
                           +------------------+


範例環境：

  • Java 8
  • Spring Boot 2.3.2.RELEASE
  • Maven 3.6.3
  • Docker 19.03.12

本範例僅在本機用Jib build image到本機的Docker daemon，所以仍要安裝Docker。

首先建立Spring Boot專案。

參考pom.xml設定。


application.properties設定如下。

#context path
server.servlet.context-path=/demo
#port
server.port=8080

新增一個DemoController處理請求。

package com.abc.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class DemoController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello World Spring Boot build by Jib Maven plugin";
    }
}

開啟命令列工具(終端機 or cmd)將工作目錄移到Spring Boot專案的根目錄下，輸入
mvn compile com.google.cloud.tools:jib-maven-plugin:2.7.0:dockerBuild
用Jib把此Spring Boot專案建置為docker image。如果是第一次用Jib build則過程中會從maven central下載依賴的函式庫。

~/../spring-boot-demo$ mvn compile com.google.cloud.tools:jib-maven-plugin:2.7.0:dockerBuild
[INFO] Scanning for projects...
Downloading from central: https://repo.maven.apache.org/maven2/com/google/cloud/tools/jib-maven-plugin/2.7.0/jib-maven-plugin-2.7.0.pom
Downloaded from central: https://repo.maven.apache.org/maven2/com/google/cloud/tools/jib-maven-plugin/2.7.0/jib-maven-plugin-2.7.0.pom (4.1 kB at 2.9 kB/s)
Downloading from central: https://repo.maven.apache.org/maven2/com/google/cloud/tools/jib-maven-plugin/2.7.0/jib-maven-plugin-2.7.0.jar
Downloaded from central: https://repo.maven.apache.org/maven2/com/google/cloud/tools/jib-maven-plugin/2.7.0/jib-maven-plugin-2.7.0.jar (537 kB at 541 kB/s)
[INFO]
[INFO] ----------------------< com.abc:spring-boot-demo >----------------------
[INFO] Building spring-boot-demo 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:3.1.0:resources (default-resources) @ spring-boot-demo ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 1 resource
[INFO] Copying 1 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ spring-boot-demo ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 2 source files to /../spring-boot-demo/target/classes
[INFO]
[INFO] --- jib-maven-plugin:2.7.0:dockerBuild (default-cli) @ spring-boot-demo ---
Downloading from central: ...
...
[INFO] Tagging image with generated image reference spring-boot-demo:0.0.1-SNAPSHOT. If you'd like to specify a different tag, you can set the <to><image> parameter in your pom.xml, or use the -Dimage=<MY IMAGE> commandline flag.
[WARNING] 'mainClass' configured in 'maven-jar-plugin' is not a valid Java class: ${start-class}
[INFO]
[INFO] Containerizing application to Docker daemon as spring-boot-demo:0.0.1-SNAPSHOT...
[WARNING] Base image 'gcr.io/distroless/java:8' does not use a specific image digest - build may not be reproducible
[INFO] Using base image with digest: sha256:90596f62a8ec0701d00845b85dfccf7f53b5e0bb3c49e275d7f19ea6c3e4565d
[INFO]
[INFO] Container entrypoint set to [java, -cp, /app/resources:/app/classes:/app/libs/*, com.abc.demo.DemoApplication]
[INFO]
[INFO] Built image to Docker daemon as spring-boot-demo:0.0.1-SNAPSHOT
[INFO] Executing tasks:
[INFO] [==============================] 100.0% complete
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  01:17 min
[INFO] Finished at: 2020-12-12T13:08:43+08:00
[INFO] ------------------------------------------------------------------------

build結束後在命令列輸入docker images即可看到建置好的專案image。image的REPOSITORY名稱預設使用Maven專案pom.xml的<artifactId>，TAG則為<version>。

$ docker images
REPOSITORY                         TAG                 IMAGE ID            CREATED             SIZE
spring-boot-demo                   0.0.1-SNAPSHOT      cc8fbb17a345        50 years ago        148MB

建立時間(CREATED)在50 years ago(or 48+ years ago)是因為Jib為了達到image的再製性(reproducibility)所以把timestamp移除的結果。

輸入$ docker run -p 8080:8080 --name demo spring-boot-demo:0.0.1-SNAPSHOT啟動spring-boot-demo container。

$ docker run -p 8080:8080 --name demo spring-boot-demo:0.0.1-SNAPSHOT

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.3.2.RELEASE)

2020-12-12 09:44:56.770  INFO 1 --- [           main] c.a.d.DemoApplication                    : Starting DemoApplication on 4c779dd36d5a with PID 1 (/app/classes started by root in /)
2020-12-12 09:44:56.786  INFO 1 --- [           main] c.a.d.DemoApplication                    : No active profile set, falling back to default profiles: default
2020-12-12 09:44:58.247  INFO 1 --- [           main] o.s.b.w.e.t.TomcatWebServer              : Tomcat initialized with port(s): 8080 (http)
2020-12-12 09:44:58.283  INFO 1 --- [           main] o.a.c.c.StandardService                  : Starting service [Tomcat]
2020-12-12 09:44:58.284  INFO 1 --- [           main] o.a.c.c.StandardEngine                   : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-12-12 09:44:58.396  INFO 1 --- [           main] o.a.c.c.C.[.[.[/demo]                    : Initializing Spring embedded WebApplicationContext
2020-12-12 09:44:58.397  INFO 1 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1533 ms
2020-12-12 09:44:58.693  INFO 1 --- [           main] o.s.s.c.ThreadPoolTaskExecutor           : Initializing ExecutorService 'applicationTaskExecutor'
2020-12-12 09:44:59.002  INFO 1 --- [           main] o.s.b.w.e.t.TomcatWebServer              : Tomcat started on port(s): 8080 (http) with context path '/demo'
2020-12-12 09:44:59.019  INFO 1 --- [           main] c.a.d.DemoApplication                    : Started DemoApplication in 3.006 seconds (JVM running for 4.172)

在瀏覽器位址輸入http://localhost:8080/demo/hello會回傳以下。這邊的Spring Boot即為運行的spring-boot-demo container。



輸入docker ps檢視運行中的spring-boot-demo container。

$ docker ps
CONTAINER ID        IMAGE                             COMMAND                  CREATED             STATUS              PORTS                    NAMES
4c779dd36d5a        spring-boot-demo:0.0.1-SNAPSHOT   "java -cp /app/resou…"   9 minutes ago       Up 4 seconds        0.0.0.0:8080->8080/tcp   demo

參考github。


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