If the application is built on JSF some times we might an faced an error like "Absent code attribute in method". This kind of issue we might have faced when we set up the applications.

 Possible reasons: 
 1. Main reason for this error is, we don't have required libraries in class path.
 2. There might be a conflict between two versions of the same jar.
 3. There is a possibility same class name exists in different jar files.

java.lang.ClassFormatError: Absent Code attribute in method that is not native or abstract in class file javax/faces/webapp/FacesServlet
 at java.lang.ClassLoader.defineClass1(Native Method)
 at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
 at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
 at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2904)
 at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1173)
 at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1681)
 at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1559)
 at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:527)
 at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:509)
 at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:137)
 at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1137)
 at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1081)
 at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:5033)
 at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5320)
 at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
 at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
 at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
 at java.util.concurrent.FutureTask.run(FutureTask.java:262)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
 at java.lang.Thread.run(Thread.java:745)