[Solved] java.lang.IncompatibleClassChangeError: Implementing class

When you are working with java libraries which internally depends on cglib, then its very normal to encounter the below error:

Exception in thread "main" java.lang.IncompatibleClassChangeError: Implementing class
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at net.sf.cglib.core.DebuggingClassWriter.toByteArray(DebuggingClassWriter.java:73)
at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:26)
at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216)
at net.sf.cglib.core.KeyFactory$Generator.create(KeyFactory.java:144)
at net.sf.cglib.core.KeyFactory.create(KeyFactory.java:116)
at net.sf.cglib.core.KeyFactory.create(KeyFactory.java:108)
at net.sf.cglib.core.KeyFactory.create(KeyFactory.java:104)
at net.sf.cglib.proxy.Enhancer.(Enhancer.java:69)

This error is due to incompatible version of cglib with additional jar files in you project, such as asm. I encountered it when writing my experiment relted to lazy loading in iBatis.

Solution

Solution is very easy. Just place the suitable version of cglib in your class path.

A correct dependency will look like this:

<dependency>
	<groupId>cglib</groupId>
	<artifactId>cglib</artifactId>
	<version>2.2.2</version>
</dependency>
<dependency>
	<groupId>asm</groupId>
	<artifactId>asm-util</artifactId>
	<version>3.3.1</version>
</dependency>

Happy Learning !!