I have had an interesting issue wiht NoClassDefFoundError in JavaEE working with Liberty server. I was using IMS resource adapters and my server.xml had already resource adapter for imsudbJXA.rar. When I added new adapter for imsudbXA.rar, I would start getting this error for instance objects for DLIException, IMSConnectionSpec or SQLInteractionSpec. I could not figure why but I resolved it by creating new server.xml for my work using only imsudbXA.rar. I am sure using multiple resource adapters in server.xml is fine, I just had no time to look into that.

更新[https://www.infoq.com/articles/single-file-execution-java11/]:

在Java SE 11中，可以选择启动单个源代码文件 直接，不需要中间编译。为了方便大家， 所以像你这样的新手不需要运行javac + Java(当然， 让他们感到困惑)。

当我将另一个模块的Maven依赖添加到我的项目中时，我得到了这个错误，这个问题最终通过添加-Xss2m到我的程序的JVM选项来解决(自JDK5.0以来默认是1m字节)。人们认为程序没有足够的堆栈来加载类。

I have had an interesting issue wiht NoClassDefFoundError in JavaEE working with Liberty server. I was using IMS resource adapters and my server.xml had already resource adapter for imsudbJXA.rar. When I added new adapter for imsudbXA.rar, I would start getting this error for instance objects for DLIException, IMSConnectionSpec or SQLInteractionSpec. I could not figure why but I resolved it by creating new server.xml for my work using only imsudbXA.rar. I am sure using multiple resource adapters in server.xml is fine, I just had no time to look into that.

我也遇到了同样的问题，我的存货积压了好几个小时。

我找到了解决办法。在我的例子中，有一个静态方法因此而定义。JVM不能创建该类的另一个对象。

例如,

private static HttpHost proxy = new HttpHost(proxyHost, Integer.valueOf(proxyPort), "http");

Java ClassNotFoundException vs NoClassDefFoundError

黑ClassLoader铝

静态与动态类加载

静态(隐式)类加载——引用、实例化或继承的结果。

MyClass myClass = new MyClass();

动态(显式)类加载是class . forname ()， loadClass()， findSystemClass()的结果

MyClass myClass = (MyClass) Class.forName("MyClass").newInstance();

每个类都有一个ClassLoader，它使用loadClass(字符串名);这就是为什么

explicit class loader uses implicit class loader

NoClassDefFoundError是显式类装入器的一部分。Error是为了保证在编译期间出现这个类，但现在(在运行时)它不存在。

ClassNotFoundException是隐式类装入器的一部分。Exception对于可以额外使用的场景(例如反射)具有弹性。