设置JAR的类路径 [英] Setting classpath for a JAR

问题描述

我有一个独立的java项目。我已经完成了maven clean安装。我现在通过命令提示符进入target\classes文件夹，并在classpath中设置所有必需的文件。现在我执行主类。结果显示出来。

I have a standalone java project. I have performed a maven clean install. I now go into the target\classes folder via command prompt and set all the required files in classpath. Now I execute the main class. The result is being displayed.

现在我通过命令提示符移回目标文件夹并尝试执行jar文件（jar文件有一个清单文件，其中定义了主类）。

Now I move back to target folder via command prompt and try to execute the jar file (jar file has a manifest file where the main class is defined).

Java -cp %CLASSPATH% -jar Destination-01.19-SNAPSHOT.jar

现在我得到以下异常。我还从上面的语句中删除了classpath属性，但仍然得到了相同的异常。在classpath变量中设置了所需的类，这就是我能够在不使用-jar属性的情况下运行主类的原因。

Now I get the below exception. I have also removed the classpath attribute from the statement above but still get the same exception.The required class is set in classpath variable which is the reason why I was able to run the main class without using the -jar attribute.

线程主线程中的异常java.lang.NoClassDefFoundError：org / apache / co
mons / logging / LogFactory

Exception in thread "Main Thread" java.lang.NoClassDefFoundError: org/apache/co mons/logging/LogFactory

推荐答案

当您使用 -jar 时，这是设置程序类路径的唯一机制。

When you use -jar this is the sole mechanism setting the classpath for the program.

您必须在清单中的Class-Path行中列出您需要的所有jar（这意味着它们需要在本地文件系统中找到）或者创建一个能够定位的自定义类加载器你需要的罐子。

You must either have all the jars you need listed in the Class-Path line in the manifest (which implies they need to be findable in the local file system) or create a custom class loader capable of locating the jar you need.

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