运行jar时NoClassDefFound [英] NoClassDefFound when running a jar

问题描述

我使用IntelliJ构建了一个jar，正确设置了主类。

I built a jar using IntelliJ, setting the main class properly.

当我从命令行（Windows）运行java -jar foo.jar时，我得到一个声称主文件丢失的异常。主类类似于：

When I run "java -jar foo.jar" from the command line (Windows), I get an exception that claims the main file is missing. The main class looks something like:

package mypackage;

public class LockUtil {
  public static void main(String[] args) {
  ...

我收到以下异常：

Exception in thread "main" java.lang.NoClassDefFoundError: mypackage/LockUtil
Caused by: java.lang.ClassNotFoundException: mypackage.LockUtil
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Could not find the main class: mypackage.LockUtil. Program will exit.

清单文件包含：

Manifest-Version: 1.0
Created-By: IntelliJ IDEA
Main-Class: mypackage.LockUtil

并且jar包含带有.class文件的相应目录结构。

And the jar contains the appropriate directory structure with the .class file.

推荐答案

如果你做了 java -tf foo.jar ，你会看到类似的东西吗？

If you do java -tf foo.jar, do you see something like this?

META-INF/
META-INF/MANIFEST.MF
mypackage/
mypackage/LockUtil.class

可能是某个地方还有另一个目录级别吗？

Could it be that there is another directory level in there somewhere?

你可以肯定Java知道主文件是通过使用以下内容构建jar文件：

You can be sure that Java knows the main file is there by building the jar file with something like this:

jar cfe foo.jar mypackage.LockUtil mypackage/LockUtil.class

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