Description and Symptoms
Exception in thread "main"
java.lang.NoClassDefFoundError is one of the most complex problems that you can
face when developing Java applications. This error is thrown by the JVM at
runtime when it is unable to locate a particular Java class from the current
Thread context class loader.
Sample
Error
java.lang.NoClassDefFoundError: Could not
initialize class org.ph.javaee.training2.ClassA
at org.ph.javaee.training2.NoClassDefFoundErrorSimulator.main(NoClassDefFoundErrorSimulator.java:32)
java.lang.ExceptionInInitializerError
at
org.ph.javaee.training2.NoClassDefFoundErrorSimulator.main(NoClassDefFoundErrorSimulator.java:23)
Caused by:
java.lang.IllegalStateException: ClassA.initStaticVariable(): Internal Error!
at
org.ph.javaee.training2.ClassA.initStaticVariable(ClassA.java:37)
at
org.ph.javaee.training2.ClassA.<clinit>(ClassA.java:16)
... 1 more
Possible
causes
- Missing Java class and/or JAR file(s) from your Java
runtime classpath.
- Failure of a static variable or initializer block at
class loading time.
- Packaging problem of your application or third part
API causing a mixed-up of class loading between the parent and child class
loaders.
- Wrong Class loader delegation model based on your
application and packaging requirements.
Troubleshooting
and solutions
- First identify the Java class the JVM is complaining
about.
- Check for a simple root cause first: wrong Java
runtime classpath.
- If the problem persists, verify if the affected Java
class contains static initializers e.g. static variable and/or static block
initializer. Look for any failure at class loading time.
- Once the above items are ruled out, perform an
assessment of your application runtime class loader delegation model and
look for any packing problem.
References
and Case Studies
