java NetBeans 制作的 jar 文件不起作用
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NetBeans-made jar file won't work
提问by Bluefire
So I made this (very simple) program with a swing GUI with NetBeans, and I clicked build to make a jar file. When I run it by double clicking it, it tells me it could not find the main class, which, after checking, I am sure is definitely there. But, when I run it from Command Prompt, it works perfectly. Any easily-determinable reason for this strange behaviour (if you want the source code, I can post it here)?
所以我用 NetBeans 用一个 Swing GUI 制作了这个（非常简单的）程序，然后我点击 build 来制作一个 jar 文件。当我通过双击运行它时，它告诉我它找不到主类，经过检查，我确信它肯定存在。但是，当我从命令提示符运行它时，它运行良好。这种奇怪行为的任何易于确定的原因（如果你想要源代码，我可以在这里发布）？
回答by csd
The things that seem to be needed in NetBeans are:
NetBeans 中似乎需要的东西是：
- The project has to be the Main Project (by right clicking on it in the Projects list).
- You have to set the Main Class in the project properties. (Right click, Properties, Run, Main Class.)
- 该项目必须是主项目（通过在项目列表中右键单击它）。
- 您必须在项目属性中设置主类。（右键单击，属性，运行，主类。）
Then when you right click on your project and do a "Clean and Build", a jar will get built into the distsubdirectory.
然后，当您右键单击您的项目并执行“清理并构建”时，将在dist子目录中构建一个 jar 。
If that fails to fix the problem, here's a longer story...
如果这不能解决问题，这里有一个更长的故事......
When you double click a jar file to run it, the operating system acts as if you had typed this from the command line:
当你双击一个 jar 文件来运行它时，操作系统的行为就像你从命令行输入的一样：
java -jar filename.jar
(When you say it works for you from the command line, is this what you're typing?)
（当您从命令行说它对您有用时，这是您正在输入的内容吗？）
At that point, the Java executable looks for a file inside the jar named META-INF/MANIFEST.MF. And then in the contents of that file, it looks for the value of a property, Main-Class. And finally it looks for the class of that name in your jar and runs its static main(String[])method.
此时，Java 可执行文件会在 jar 中查找名为META-INF/MANIFEST.MF. 然后在该文件的内容中查找属性的值Main-Class. 最后，它会在您的 jar 中查找该名称的类并运行其静态main(String[])方法。
So if your jar is failing to run, you can do the following to debug what's going on:
因此，如果您的 jar 无法运行，您可以执行以下操作来调试正在发生的事情：
- Clean and rebuild your project in NetBeans.
- Double check that your class(es) are actually in the jar:
- Start a command prompt
cdinto thedistsubdirectory of your project.- Use a command like
jar tf filename.jarto list what's in there.
- Double check that the
MANIFEST.MFfile is correct:- Again in a command prompt
cdinto thedistdirectory.- Use a command like
jar xf filename.jar META-INF/MANIFEST.MFto extract the manifest. - Look at the contents of that file (e.g.
type META-INF\MANIFEST.MF) and make sureMain-Classis set to the appropriate class.
- 在 NetBeans 中清理并重建您的项目。
- 仔细检查您的课程是否确实在 jar 中：
- 启动命令提示符
cd进入dist你的项目的子目录。- 使用命令 like
jar tf filename.jar列出里面的内容。
- 仔细检查
MANIFEST.MF文件是否正确：- 再次在命令提示符中
cd进入dist目录。- 使用像
jar xf filename.jar META-INF/MANIFEST.MF提取清单的命令。 - 查看该文件的内容（例如
type META-INF\MANIFEST.MF）并确保Main-Class已设置为适当的类。
If all of the above check out, then double clicking the file shouldwork.
如果以上所有检查都通过，则双击该文件应该可以工作。
回答by BlackVegetable
Have you set the containing project as the "Main Project"?
您是否将包含项目设置为“主项目”？
