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java.lang.ClassFormatError: Absent Code attribute 

Fang
Joined:
08/13/2009
Posts:
164

October 22, 2011 19:51:05    Last update: October 22, 2011 20:31:48
I built a very basic JSF application and deployed to Tomcat 7.0.22, but it failed with this error: 
Caused by: 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.defineClassCond(ClassLoader.java:631)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
	at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2820)

That looks weird and I wasn't able to find a sensible explanation!

So I copied the jsf-api-2.1.jar, which was downloaded from the java.net Maven repository by Maven, into a temp folder. And tested it with this simple program: 
public class ClassFormatErrorTest {
    public static void main(String[] args) throws Exception {
	Class.forName("javax.faces.webapp.FacesServlet");
    }
}

I also copied servlet-api.jar from Tomcat's lib folder to the temp folder. Sure enough it failed with the same error: 
C:\tmp>java -cp .;jsf-api-2.1.jar;servlet-api.jar ClassFormatErrorTest
Exception in thread "main" 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.defineClassCond(ClassLoader.java:631)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:169)
        at ClassFormatErrorTest.main(ClassFormatErrorTest.java:3)

But when I replaced the javax.faces.webapp.FacesServlet class with one I compiled from source, the error disappears!

Conclusions:
  1. The jar file jsf-api-2.1.jar from java.net Maven repository is good for compilation only (cannot be used at runtime). The javax.faces.webapp.FacesServlet class inside it is just an empty shell without code.
  2. The class is not generated by normal Java compilation with javac.
  3. How to generate an "empty shell" class file remains a mystery to me!
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