Gradle Kotlin DSL:无法找到或加载主类

Question

我有一个Java项目，有多个依赖项，我想用Kotlin DSL将其打包到Gradle的fat jar中。

当我运行./gradlew jar时，构建成功，但当我试图运行它时，它找不到主类:

$ ./gradlew jar
BUILD SUCCESSFUL in 1s
2 actionable tasks: 2 executed
$ java -jar build/libs/myapp-0.0.1-SNAPSHOT.jar
Error: Could not find or load main class mypackage.Hello
Caused by: java.lang.ClassNotFoundException: mypackage.Hello
$ jar xf build/libs/myapp-0.0.1-SNAPSHOT.jar META-INF/MANIFEST.MF
$ cat META-INF/MANIFEST.MF
Manifest-Version: 1.0
Main-Class: mypackage.Hello
$ jar -tf build/libs/myapp-0.0.1-SNAPSHOT.jar | grep mypackage                                                          1
mypackage/
mypackage/Hello.class

以下是完整的build.gradle.kts文件:

group = "myapp"
version = "0.0.1-SNAPSHOT"
java {
sourceCompatibility = JavaVersion.VERSION_1_8
targetCompatibility = JavaVersion.VERSION_1_8
withSourcesJar()
}
plugins {
java
}
repositories {
mavenCentral()
maven {
url = uri("https://mvnrepository.com/artifact/com.microsoft.azure/azure-storage")
}
}
dependencies {
implementation("com.azure:azure-storage-blob:12.12.0")
}
val mainClassName = "mypackage.Hello"
tasks.jar {
duplicatesStrategy = DuplicatesStrategy.INCLUDE
manifest.attributes.apply {
put("Class-Path", configurations.runtimeClasspath.get().asPath)
put("Main-Class", mainClassName)
}
from(configurations.compileClasspath.get().map { if (it.isDirectory) it else zipTree(it) })
}
tasks.test {
useJUnitPlatform()
}

和一个链接到我的repo: https://github.com/darkasphalt/myapp

Answer 1

检查jar的内容。问题是，您包含了库中的所有内容。这也增加了来自java模块系统的文件，如module-info.class。这可能会隐藏你的Main类。

简单修复

你的主要作品，如果你:

)删除导入
implementation("com.azure:azure-storage-blob:12.12.0")
或
b)删除类路径配置:
from(configurations.compileClasspath.get().map { if (it.isDirectory) it else zipTree(it) })

那么简单的java -jar myapp-0.0.1-SNAPSHOT.jar将打印出:

你好

安装ShadowJar

要解决以正确的方式打包一个fat jar的问题，你可以使用ShadowJar插件。有了这样的设置，绑定的jar就可以工作了:

import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
group = "myapp"
version = "0.0.1-SNAPSHOT"
plugins {
java
application
id("com.github.johnrengelman.shadow").version("7.0.0")
}
java {
sourceCompatibility = JavaVersion.VERSION_1_8
targetCompatibility = JavaVersion.VERSION_1_8
withSourcesJar()
}

repositories {
mavenCentral()
maven {
url = uri("https://mvnrepository.com/artifact/com.microsoft.azure/azure-storage")
}
}
application() {
mainClass.set("mypackage.Hello")
}
dependencies {
implementation("com.azure:azure-storage-blob:12.12.0")
}
// Configure Shadow to output with normal jar file name:
tasks.named<ShadowJar>("shadowJar").configure {
minimize()
}
tasks {
build {
dependsOn(shadowJar)
}
}
tasks.test {
useJUnitPlatform()
}