文件中没有主清单属性，在jar包中。

我有一个使用Gradle的spring项目。我在build.gradle中创建了一个任务：

task dockerFile(type: Dockerfile) {
    destFile.set(project.file('Dockerfile'))
    from "alpine:$alpineVersion"
    runCommand 'apk add --no-cache openjdk11'
    copyFile "build/libs/${jar.archiveFileName.get()}", '/app/'
    workingDir '/app/'
    entryPoint 'java'
    defaultCommand '-jar', "/app/${jar.archiveFileName.get()}"
}

一切都很好。生成了Dockerfile。但是当我尝试运行该镜像时，它会出现错误：/app/demo-0.0.1-SNAPSHOT-plain.jar中没有主清单属性

这是我的整个build.gradle：

import com.bmuschko.gradle.docker.tasks.image.Dockerfile
plugins {
    id 'java'
    id 'org.springframework.boot' version '2.7.6'
    id 'io.spring.dependency-management' version '1.0.15.RELEASE'
    id 'com.bmuschko.docker-remote-api' version '6.6.1' apply false
}
group = 'ms10gradle2'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'
configurations {
    compileOnly {
        extendsFrom annotationProcessor
    }
}
repositories {
    mavenCentral()
}
dependencies {
    implementation "org.springframework.boot:spring-boot-starter-data-jpa:$jpaVersion"
    implementation 'org.springframework.boot:spring-boot-starter-web'
    compileOnly 'org.projectlombok:lombok'
    runtimeOnly 'com.h2database:h2'
    annotationProcessor 'org.projectlombok:lombok'
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
}
tasks.named('test') {
    useJUnitPlatform()
}
task printJpaVer{
    print "JPA VERSION: ${jpaVersion}"
}
task printfiles {
   doLast {
       def files = "cmd.exe /c dir".execute().text.trim()
       println(files)
       project.getAllprojects().forEach(System.out::print)
   }
}
task printTasks{
    project.getTasks().forEach{
        println("task name: "+ it)
    }
}
task printTasksInsideSubModulesTrueOrFalse{
    project.getAllTasks(false).entrySet().forEach(System.out::println)
}
task printTaskVersion{
    project.getAllprojects()
        .forEach(p -> println p.name +"- "+p.getVersion())
    print "================================================================"
    project.getAllprojects().forEach(p -> println p.getVersion())
}
task dockerFile(type: Dockerfile) {
    destFile.set(project.file('Dockerfile'))
    from "alpine:$alpineVersion"
    runCommand 'apk add --no-cache openjdk11'
    copyFile "build/libs/${jar.archiveFileName.get()}", '/app/'
    workingDir '/app/'
    entryPoint 'java'
    defaultCommand '-jar', "/app/${jar.archiveFileName.get()}"
}

以及Dockerfile：

FROM alpine:3.11.2
RUN apk add --no-cache openjdk11
COPY build/libs/demo-0.0.1-SNAPSHOT-plain.jar /app/
WORKDIR /app/
ENTRYPOINT ["java"]
CMD ["-jar", "/app/demo-0.0.1-SNAPSHOT-plain.jar"]