On my servlet program I'm calling a file(given in HTML with herf action)whichgo to server and that server file pick up data from particular table(which determined previously) and show its data. But as I performed click on one line given with herf in herfHTML doc.it shows error of NULL Pointer Exception. Why It all this? Tell me where I'm wrong. tomcat server is in functioning.
As with any exception: Look at the stack trace of the exception. It shows you exactly in which line of code in which source file the exception happened. Go to that place in your source code and think what could be null there.