If you use Maven in your project for dependency management and if you use it a lot then sometimes you get into weird classpath issues where more than one version of JAR is loaded. Most of times I have got into issues related to cglib library. If two versions of cglibs, like cglib-2.1.1.jar and cglib-nodep.jar are present in your classpath then its likely you get into trouble.
Maven automatically includes the transitive dependencies in your project. This can cause different versions of same JAR to be fetched.
To avoid this, you can use Maven’s <exclusions> tag. Consider below Maven dependency of spring-json library.