Question

我已经按照这些教程为Spring Boot应用程序构建Docker映像，该应用程序使用Maven作为构建工具。我在Windows 10计算机上使用boot2docker VM，将我的项目从Bitbucker存储库克隆到VM。

https://spring.io/guides/gs/spring-boot-docker/

https://www.callicoder.com/spring-boot-docker-example/

我了解其中的说明，但是，我无法构建正确的Docker映像。这是我尝试过的事情。

使用适用于Dockerfile的Spotify maven插件。尝试运行./mvnw来构建JAR和Docker映像。但是，我没有在boot2docker中安装Java。因此Maven包装器./mvnw无法运行。
我试图通过Dockerfile构建JAR，该文件基于openjdk：8-jdk-alpine映像。我在Dockerfile中添加了RUN ./mvnw package指令。然后运行docker build -t <my_project> .来构建Docker镜像。它在RUN指令处失败，声称/bin/sh: mvnw: not found The command '/bin/sh -c mvnw package' returned a non-zero code: 127

我的Dockerfile，位于mvnw所在的目录中：

MAINTAINER myname

VOLUME /tmp

RUN ./mvnw package

ARG JAR_FILE=target/myproject-0.0.1-SNAPSHOT.jar

COPY ${JAR_FILE} app.jar

ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

对于1，我需要在Docker引擎所在的操作系统中安装Java。但是我认为这不是一个好习惯，因为这会降低可移植性。

对于2，首先，我不知道如何在Dockerfile中成功运行./mvnw。其次，我不确定通过Dockerfile来构建Spring Boot JAR是否是一个好习惯，因为我看不到任何“ Docker for Spring Boot”教程可以告诉您这样做。

那么，解决我的情况的最佳实践是什么？我是Docker的新手。评论和答案表示赞赏！

Answer 1

您可以安装maven并直接在构建中运行编译。通常，这是一个多阶段构建，以避免将整个jdk包含在推送的图像中：

FROM openjdk:8-jdk-alpine as build
RUN apk add --no-cache maven
WORKDIR /java
COPY . /java
RUN mvn package -Dmaven.test.skip=true
EXPOSE 8080
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/java/target/myproject-0.0.1-SNAPSHOT.jar"]

以上是我过去做过的同一示例的精简版。您可能需要在入口点调整文件名，但关键步骤是安装maven并在内部版本中运行它。

Answer 2

从您的第二个示例中，我认为您误解了 Docker 构建图像的方式。当 Docker 执行 RUN ./mvnw package 时，文件 mvnw 必须存在于正在构建的镜像的文件系统中，这意味着您应该在上一步中有一个类似 COPY mvnw . 的指令 - 它将复制将本地文件系统中的文件复制到映像中。

您可能需要在调用 ./mvnw 之前复制图像中的整个项目结构，正如@BMitch 的回复所建议的那样。

此外，正如@BMitch 所说，要生成小尺寸映像，通常建议使用多阶段构建，其中第一阶段安装所有依赖项，但最终映像只有您的 JAR。

您可以尝试以下操作：

# First stage: build fat JAR

# Select base image.
# (The "AS builder" gives a name to the stage that we will need later)
# (I think it's better to use a slim image with Maven already installed instead
#  than ./mvnw. Otherwise you could need to give execution rights to your file
#  with instructions like "RUN chmod +x mvnw".)
FROM maven:3.6.3-openjdk-8-slim AS builder

# Set your preferred working directory
# (This tells the image what the "current" directory is for the rest of the build)
WORKDIR /opt/app

# Copy everything from you current local directory into the working directory of the image
COPY . .

# Compile, test and package
# (-e gives more information in case of errors)
# (I prefer to also run unit tests at this point. This may not be possible if your tests
#  depend on other technologies that you don't whish to install at this point.)
RUN mvn -e clean verify

###

# Second stage: final image containing only WAR files

# The base image for the final result can be as small as Alpine with a JRE
FROM openjdk:8-jre-alpine

# Once again, the current directory as seen by your image
WORKDIR /opt/app

# Get artifacts from the previous stage and copy them to the new image.
# (If you are confident the only JAR in "target/" is your package, you could NOT
#  use the full name of the JAR and instead something like "*.jar", to avoid updating
#  the Dockerfile when the version of your project changes.)
COPY --from=builder /opt/app/target/*.jar ./

# Expose whichever port you use in the Spring application
EXPOSE 8080

# Define the application to run when the Docker container is created.
# Either ENTRYPOINT or CMD.
# (Optionally, you could define a file "entrypoint.sh" that can have a more complex
#  startup logic.)
# (Setting "java.security.egd" when running Spring applications is good for security
#  reasons.)
ENTRYPOINT java -Djava.security.egd=file:/dev/./urandom -jar /opt/app/*.war

如何在没有JAR的情况下为Spring Boot应用程序构建Docker映像

2 个答案: