Why I'm Getting java.lang.NoClassDefFoundError while using jar which use poi jars

Question

I'm using Eclipse in order to compile & run Java applications. I'm creating several projects, which I export as a jar file and import (add to build path) them as jar file in the other projects. I add the jar as follows:

• copy the jar to the project I want
• right click on the jar -> build path -> add to build path

It is my first time I'm getting this error:

java.lang.NoClassDefFoundError

I created a project which uses POI jars. The project name is "A". I export this project to A.jar file and import it (add to build path) in B project. When I'm running the B project and try to init (call the constructor) of an object from A.jar, I'm getting the following error:

java.lang.NoClassDefFoundError: org/apache/poi/ss/usermodel/CellStyle

I checked the following threads:

• Why am I getting a NoClassDefFoundError in Java?
• java.lang.NoClassDefFoundError while running jar

But didn't find the answer.

1. Why am I getting this error? It isn't my first time, that I'm importing/adding to build path. But now I'm getting an error.

2. How can I solve it?

Answer 1

1. You get the error, because the classloader do not find the class.

2. You have to add the jar that containing the class poi-<version>.jar to the classpath.

The build path only defined the path for the compiler. It not define that the class is in the classpath at runtime.