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in servlet i am taking value from URL String callback = request.getParameter("_callback"); problem is &_callback can be there or not, i am getting nullPointerException if &_callback is not there in URL. I tried to catch the exception but didn't work. is there any way to check whether request.getParameter() is null or not? if it is null, i want to execute a part of code and if not, other part.
getParameter returns the value of a request parameter as a String, or null if the parameter does not exist. It does not through NullPointerException if parameter does not exist. Make sure that the request object on which you are calling getParameter is not null. Look at this servlet request Article for details on methods for request parameters.