Hi Preety Sharma ,
Please refer to below links where in I have explained how to call a servlet and 3rd party database using different jar files.
SAP UI5 - Calling Servlet(which Returns Single Value) using JQUERY AJAX
SAP UI5 - CALLING SERVLET (RETURNING MULTIPLE VALUES) USING JQUERY,AJAX AND JSON.
SAP UI5 – CALLING EXTERNAL DATABASE MYSQL THROUGH "HIBERNATE"
Regards,
Varun