作为servlet工作但不作为java类工作。为什么？

I am working on SAML SSO Authentication. I have created a servlet to generate SAML metadata and i deployed it and run it and I got the output. Same time I have created a java class to generate SAML Metadata with the same code and tried to run it independently. I have added the same Jar files that I have used for that servlet application. But I got the Exception given below. Can anybody help me to find the difference between running an application independently and by using java servlet?? Thanks in advance.I am working on SAML SSO Authentication. I have