java - NoClassDefFoundError 是否总是由 ClassNotFoundException 引起？

Question

我可以假设从 JDK 类加载机制抛出的每个 NoClassDefFoundError 总是在堆栈跟踪中将 ClassNotFoundException 作为原因吗？

另外，NoClassDefFoundError实际上是在哪里抛出的，并且它的原因被初始化为ClassNotFoundException？我找不到负责该逻辑的 Java 代码。

这就是我通常看到的堆栈跟踪:

Exception in thread "main" java.lang.NoClassDefFoundError: package/Missing
    at package.Missing(Missing.java:110)
Caused by: java.lang.ClassNotFoundException: package.Missing
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 1 more

Answer 1

Can I assume that every NoClassDefFoundError thrown from JDK class loading mechanism will always have ClassNotFoundException as a cause in stacktrace?

这是一个合理的假设。根据Java Virtual Machine Specification :

If the Java Virtual Machine ever attempts to load a class C during verification (§5.4.1) or resolution (§5.4.3) (but not initialization (§5.5)), and the class loader that is used to initiate loading of C throws an instance of ClassNotFoundException, then the Java Virtual Machine must throw an instance of NoClassDefFoundError whose cause is the instance of ClassNotFoundException.

我相信以上也回答了你的第二个问题。