无法执行jar文件：“无主清单属性” [英] Can't execute jar- file: "no main manifest attribute"

问题描述

我已经安装了一个应用程序，当我尝试运行它时（它是一个可执行的jar）没有任何反应。当我从命令行运行它时：

I have installed an application, when I try to run it (it's an executable jar) nothing happens. When I run it from the commandline with:

java -jarapp.jar

java -jar "app.jar"

我收到以下消息：

在app.jar中没有主要清单属性

no main manifest attribute, in "app.jar"

通常情况下，如果我自己创建了程序，我会在清单文件中添加一个主类属性。但在这种情况下，由于文件来自应用程序，我不能这样做。我也尝试提取jar以查看是否可以找到主类，但是有许多类，并且它们中没有一个在其名称中包含main一词。必须有办法解决这个问题，因为该程序在其他系统上运行良好。

Normally, if I had created the program myself, I would have added a main class attribute to the manifest file. But in this case, since the file is from an application, i cannot do that. I also tried extracting the jar to see if I could find the main class, but there are to many classes and none of them has the word "main" in it's name. There must be a way to fix this because the program runs fine on other systems.

推荐答案

首先，它有点奇怪，看你运行 java -jarapp而不是 java -jar app.jar

First, it's kind of weird, to see you run java -jar "app" and not java -jar app.jar

其次，要制作一个jar可执行文件...你需要jar一个名为META-INF / MANIFEST.MF的文件

Second, to make a jar executable... you need to jar a file called META-INF/MANIFEST.MF

文件本身应该（至少）这一个班轮：

the file itself should have (at least) this one liner:

Main-Class: com.mypackage.MyClass

其中 com.mypackage.MyClass 是持有 public的班级static void main（String [] args）入口点。

请注意，有几种方法可以使用CLI，Maven，Ant或Gradle：

Note that there are several ways to get this done either with the CLI, Maven, Ant or Gradle:

对于 CLI ，以下命令将执行：（tks @ dvvrt ）

jar cmvf META-INF / MANIFEST.MF< new-jar-filename> .jar<要包含的文件& GT;


For CLI, the following command will do: (tks @dvvrt) jar cmvf META-INF/MANIFEST.MF <new-jar-filename>.jar <files to include>

对于 Maven ，类似以下代码段的内容应该可以解决问题。请注意，这只是插件定义，而不是完整的 pom.xml ：

For Maven, something like the following snippet should do the trick. Note that this is only the plugin definition, not the full pom.xml:

<build>
  <plugins>
    <plugin>
      <!-- Build an executable JAR -->
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-jar-plugin</artifactId>
      <version>3.1.0</version>
      <configuration>
        <archive>
          <manifest>
            <addClasspath>true</addClasspath>
            <classpathPrefix>lib/</classpathPrefix>
            <mainClass>com.mypackage.MyClass</mainClass>
          </manifest>
        </archive>
      </configuration>
    </plugin>
  </plugins>
</build>

（选择 < version> 适用于您的项目。）

(Pick a <version> appropriate to your project.)

对于 Ant ，下面的代码段应该有所帮助：

For Ant, the snippet below should help:

<jar destfile="build/main/checksites.jar">
  <fileset dir="build/main/classes"/>
  <zipfileset includes="**/*.class" src="lib/main/some.jar"/>
  <manifest>
    <attribute name="Main-Class" value="com.acme.checksites.Main"/>
  </manifest>
</jar>

积分Michael Niemand -

Credits Michael Niemand -

For Gradle ：

plugins {
    id 'java'
}

jar {
    manifest {
        attributes(
                'Main-Class': 'com.mypackage.MyClass'
        )
    }
}

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