Java EE (Java Enterprise Edition) General Discussion

Hi,
I am trying to read the contents of a XML file using the JAXB. The file is getting compiled but gives the follwing exception while running the code.
The details of the exception are below-

java.lang.ClassNotFoundException: primer.po.impl.runtime.DefaultJAXBContextImpl
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 com.sun.xml.bind.ContextFactory_1_0_1.createContext(ContextFactory_1_0_1.java:45)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:96)
at javax.xml.bind.ContextFinder.searchcontextPath(ContextFinder.java:229)
at javax.xml.bind.ContextFinder.find(ContextFinder.java:149)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:281)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:238)
at MainOne.main(MainOne.java:25)
--------------- linked to ------------------
javax.xml.bind.JAXBException
- with linked exception:
[java.lang.ClassNotFoundException: primer.po.impl.runtime.DefaultJAXBContextImpl]
at com.sun.xml.bind.ContextFactory_1_0_1.createContext(ContextFactory_1_0_1.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:96)
at javax.xml.bind.ContextFinder.searchcontextPath(ContextFinder.java:229)
at javax.xml.bind.ContextFinder.find(ContextFinder.java:149)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:281)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:238)
at MainOne.main(MainOne.java:25)

Can anybody plz tell me the root cause of this error.
Thanks in advance.