带有Maven Jar的Docker [英] docker with maven jar

问题描述

我正在docker容器中运行一个Maven项目，我得到找不到或加载主类错误.

I'm running a maven project in a docker container, I'm getting Could not find or load main class error.

FROM maven:3.6.0-jdk-11-slim AS build

COPY src src
COPY pom.xml .
RUN mvn -f pom.xml clean package install

FROM openjdk:8-jre

COPY --from=build /target /opt/target
WORKDIR /target

RUN ls

CMD ["java", "-jar", "Customer.jar"]

上面的程序集是通过< build>

<plugin>
    <artifactId>maven-assembly-plugin</artifactId>
    <configuration>
        <archive>
            <manifest>
                <mainClass>com.companyname.Customer</mainClass>
            </manifest>
        </archive>
        <descriptorRefs>
            <descriptorRef>jar-with-dependencies</descriptorRef>
        </descriptorRefs>
    </configuration>
    <executions>
        <execution>
            <id>make-assembly</id> <!-- this is used for inheritance merges -->
            <phase>package</phase> <!-- bind to the packaging phase -->
            <goals>
                <goal>single</goal>
            </goals>
        </execution>
    </executions>
</plugin>

错误

错误:找不到或加载主类com.mycompany.Customer

Error: Could not find or load main class com.mycompany.Customer

问题:如何在docker中将类路径设置为jar文件?

Question: How do you set class path to a jar file in docker?

修改

我测试了以下但相同的问题.

I tested with the following but same issue.

CMD ["java", "-cp", "Customer.jar:libs/*", "com.company.customers.Customer"]

错误:找不到或加载主类com.company.customers.Customer

Error: Could not find or load main class com.company.customers.Customer

推荐答案

这不是Docker问题，而是Java问题.定义类路径条目以运行可执行jar的方法有多种.

It's not a Docker issue it's a Java issue. There are several ways to define classpath entries to run an executable jar.

在这种情况下，您需要创建一个带阴影的jar，该jar在一个可执行的jar文件中包含所有相关类.Maven有一个名为 Apache Maven Shade插件的插件来创建该插件uber-jar工件.

In this case you sould create a shaded jar which contains all dependent classes in one executable jar file. Maven has a plugin called Apache Maven Shade Plugin to create that uber-jar artifact.

最后运行:

java -jar shaded-artifact.jar

或在Docker

CMD ["java", "-jar", "shaded-artifact.jar"]

命令行类路径方法

如果创建的jar工件需要存在其他(从属)jar，则必须指定类路径.在这种情况下，将所有需要的罐子复制到一个文件夹中，例如 lib 并使用以下命令:

java -cp '<name-of-jar.jar>:<path-of-dependencies>' <fully.quialified.main.ClassName>

如您所见，通配符(*)和多个classpath元素都可以用分隔:所以

As you can see either wildcard (*) character and multiple classpath element is allowed separated by : so

java -cp 'Customer.jar:libs/*' com.mycompany.Customer

在Docker中

CMD ["java", "-cp", "Customer.jar:libs/*", "com.mycompany.Customer"]

MANIFEST方法中的类路径

在将所有这些从属工件收集到一个文件夹中之后，您只需在 META-INF/MANIFEST.MF 中添加一个 Class-Path 条目即可.strong>像这样的文件:

Classpath in MANIFEST approach

After you collecteded all those dependent artifact into a folder then you just add a Class-Path entry into your META-INF/MANIFEST.MF file like this:

Class-Path: . lib/*

然后运行

java -jar Customer.jar

或在Docker

CMD ["java", "-jar", "Customer.jar"]

其中最好的取决于很多事情，您必须选择.

Which of those is the best depends on so many things, you have to choose.

基于更新后的问题，似乎uber jar由程序集插件使用 jar-with-dependencies 预定义描述符创建.这将创建另一个jar文件，该文件放置在目标(输出)文件夹下，其名称以 -jar-with-dependencies.jar

Based on updated question it seems the uber jar was created by assembly plugin using jar-with-dependencies predefined descriptor. This will create another jar file which placed under target (output) folder and its name ends with -jar-with-dependencies.jar

1. 使用该罐子的基本人工制品.
2. 仔细检查以确保所有< mainClass> 条目都指向现有的类.您在同一问题中提到了三个不同的主类.

1. Use that jar insead of basic artifact.
2. Do a double check to make sure all of <mainClass> entries point to an existing class. You've mentioned three different main class in the same question.

com.companyname.Customer

com.companyname.Customer

com.mycompany.Customer

com.mycompany.Customer

com.company.customers.Customer

com.company.customers.Customer

希望有帮助.

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