Gradle输出罐没有Main-Class [英] Gradle Output Jar has no Main-Class

问题描述

我有以下简单的build.gradle文件:

I have the following simple build.gradle file:

apply plugin: 'application'
apply plugin: 'java'

mainClassName = 'com.kurtis.HelloGradle'

以及位于src/main/java/com/kurtis/HelloGradle.java的以下单个Java文件:

And the following single java file located at src/main/java/com/kurtis/HelloGradle.java:

package com.kurtis;

public class HelloGradle {

    public static void main(String[] args) {

        System.out.println("Hello gradle");
    }

}

但是，如果我运行gradle build，我会在build/lib目录中得到一个没有设置主类的jar.它的清单文件没有Main-Class条目.为什么会这样?

However, if I run gradle build I get a jar in the build/lib directory that has no main class set. It's manifest file has no Main-Class entry. Why is this?

推荐答案

这是由于应用程序插件的工作方式所致. mainClassName是application插件使用的属性，当它创建可执行jar时，清单中不需要Main-Class，因为它不使用它.

It's due to the way application plugin works. mainClassName is a property used by application plugin, when it creates an executable jar, it doesn't need to have a Main-Class in the manifest, since it doesn't use it.

如果需要在jar中添加Main-Class，则必须按java插件的jar配置提供它，如下所示:

If you need to have a Main-Class in your jar, then you have to provide it vie jar configuration of the java plugin as follows:

jar {
  manifest {
    attributes(
      'Main-Class': 'com.kurtis.HelloGradle'
    )
  }
}

否则，只需使用由应用程序插件生成的可执行文件，无论是通过run任务还是通过它可以为您创建的发行版，都可以使用脚本来运行您的应用程序及其所有依赖项.

Otherwise, just use an executable, which is generated by application plugin, whether via run task or via distributions it can create for you, with scripts to run your application and all it's dependencies.

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