为什么无法从 JAR 文件加载主类清单属性? [英] Why has it failed to load main-class manifest attribute from a JAR file?

问题描述

我以这种方式创建了一个 JAR 文件 jar cf jar-file input-files.现在，我正在尝试运行它.运行它不起作用(找不到jre命令):

I have created a JAR file in this way jar cf jar-file input-files. Now, I'm trying to run it. Running it does not work (jre command is not found):

jre -cp app.jar MainClass

这也不起作用:

java -jar main.jar

(无法从 main.jar 加载主类清单属性).

(Failed to load Main-Class manifest attribute from main.jar).

我也发现了

运行打包为JAR 文件(版本 1.2 -- 需要主类清单头)

To run an application packaged as a JAR file (version 1.2 -- requires Main-Class manifest header)

什么是主类清单标头"?如何创建它以及将它放在哪里?

What is the "Main-Class manifest header"? How do I create it and where do I put it?

推荐答案

我不确定我是否相信你的症状:

I'm not sure I believe your symptoms:

• 如果没有找到 jre 命令，那么运行 jre -cp app.jar 应该会给出同样的错误
• 只需将 JAR 文件添加到类路径中不会出现错误你看到了

• If the jre command isn't found, then running jre -cp app.jar should give the same error
• Just adding a JAR file to the classpath shouldn't give the error you're seeing

如果您运行，我希望您会看到此错误:

I'd expect you to see this error if you run:

java -jar app.jar

Main-Class 标头需要在 JAR 文件的清单中 - 这是有关其他所需库等内容的元数据.请参阅 Sun 文档，了解如何创建适当的清单.基本上，您需要创建一个文本文件，其中包含如下一行:

The Main-Class header needs to be in the manifest for the JAR file - this is metadata about things like other required libraries. See the Sun documentation for how to create an appropriate manifest. Basically you need to create a text file which includes a line like this:

Main-Class: MainClass

然后运行

jar cfm app.jar manifest.txt *.class

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