NoClassDefFoundError

Question

I am using eclipse to develop my application. In my application i have few projects and those projects have reference in EAR project.

In one of project i have created a interface and impementation for that interface.

I am trying to craete object for that class

MyInterface myObj = new MyClass();

It was not working so i started server in debug mode. I am getting NoClassDefFoundError.

Any idea why i am getting this error. I have already added new project in my project build path. If i write

MyInterface myObj = null;

i do not get any error.

What *exactly* does the exception look like? Which class can't it find? — Jon Skeet, Jan 19 '11 at 07:09
adding to build path is not enough. you have to set the `binary` path to `WEB-INF/classes`. If you use web tools, it should be configured automatically. — J-16 SDiZ, Jan 19 '11 at 07:17
What other classes are referenced by MyClass? You might be missing a library. — Jochen Bedersdorfer, Jan 19 '11 at 07:42
I am getting eror message: what do i do: seems an odd quirk of the EJB spec. The exception is:java.lang.NoClassDefFoundError: — aj_us, Jan 19 '11 at 13:52

score 0 · Answer 1 · edited May 23 '17 at 10:24

This was happening to me. The problem was not that "MyClass" was missing from the classpath. What was missing in my case was one of the dependencies inside MyClass (i.e. an import) and when the constructor was called it failed.

Check my related question and the answer: Class Constructor fails throwing Exception on Class Loading as well as the question before that which is when all my problems started: Weird behavior with Constructor and Class. Application hangs `forever` on Constructor

score 0 · Answer 2 · answered Jan 19 '11 at 07:51

Check the classpath used by the runtime configuration you're running in Eclipse, which is normally defined by the project libraries and source folders.

Since you're working with an EAR, you probably use an app server, and you need to know that most of them work with one parent classloader and a child classloader per ear or war. That means that if a class loaded by a parent classloader tries to instantiate a class which is only in a child classloader you get a NoClassDefinedError (the other way around you don't).

I am getting eror message: what do i do: seems an odd quirk of the EJB spec. The exception is:java.lang.NoClassDefFoundError: — aj_us, Jan 19 '11 at 13:52

NoClassDefFoundError

2 Answers2