NoClassDefFoundError 是否总是由 ClassNotFoundException 引起的？

Question

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

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

在我看来，堆栈跟踪通常是这样的：

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.

相信以上也回答了你的第二个问题。

NoClassDefFoundError 是否总是由 ClassNotFoundException 引起的？

Does NoClassDefFoundError have always ClassNotFoundException in caused by?

java

classloader

stack-trace

noclassdeffounderror

classnotfoundexception