Ajax ,JSP and oracle database

I am using ajax,jsp and oracle in my project.In this when i type emp id and select date ,then it will access data/info(regarding that employee) from the database without refreshing the page and show it in the text boxes(data as per empID and date).I am new to ajax.please tell me detailed procedure how can i get the data from the database and show it in jsp page txt boxes.To access database I use entity objects and view objects in jdeveloper.