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problem in retriving List objects

Greenhorn

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posted 11 years ago

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Hello, i am trying to print values in a jsp page Customer.jsp taken from AccountDetailDAO. At first page goes through LoginValidation but i am getting NullPointerException in line 83.
It works fine when i am login as a manager.
Here are the relevant codes
LoginValidation.java

if(user=="" || pass=="")
			{
				out.println("Username or password cannot be empty");
				rd=request.getRequestDispatcher("LogIn.jsp");
				rd.include(request, response);
			}
			else
			{
			st=conn.prepareStatement("select role from login where username=? and password=?");
			st.setString(1, user);
			st.setString(2, pass);
			rs=st.executeQuery();
			if(rs.next())
			{
				role=rs.getString(1);
				sess.setAttribute("role",role);
				sess.setAttribute("user",user);
				sess.setAttribute("pass",pass);
				if(role.equals("customer"))
				{
					dao.getConnection();
					List<AccountDetail> actdtl=dao.getAccountno();
					request.setAttribute("accountno", actdtl);
					
					rd=request.getRequestDispatcher("Customer.jsp");
					rd.forward(request, response);                                       //Line 83
					
				}
				else if(role.equals("manager"))
				{
					rd=request.getRequestDispatcher("Manager.jsp");
					rd.forward(request, response);
				}
						}
			else{
				out.println("Wrong username or password. LogIn again");
				rd=request.getRequestDispatcher("LogIn.jsp");
				rd.include(request, response);
			}
			}

Customer.jsp

AccountDetailDAO

Jeanne Boyarsky

author & internet detective

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posted 11 years ago

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Which line is line 83?

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Amit Kumar Thakur

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posted 11 years ago

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I have already marked that in LoginValidaion.java .

Avinash venna

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posted 11 years ago

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the getDispatcher method takes path as an argument. most probably the path here is wrong. Try checking that.. you may try /Customer.jsp

Alex Theedom

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posted 11 years ago

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A null pointer will occur if a method is called on an object that is null and according to the API doc the getRequestDispatcher() method "returns null if the servlet container cannot return a RequestDispatcher".

I attempted to replicate this in my environment without success. I am using Tomcat 7 and if the path argument in the getRequestDispatcher() is not valid it does not throw a null pointer exception, instead the servlet sends an HTTP 404 message code to the browser.

Investigating this further I found this post by Charles Lyons that talks in detail about this: https://coderanch.com/t/453276/java-Web-Component-SCWCD/certification/RequestDispatcher-null-outcome. It appears that server implementation determines the behaviour.

Would you post the stack trace if correcting the path does not solve it.

Alex Theedom. Author of: Java EE Video Courses (JAX-RS, Bean Validation, Websocket, JSON-P and much more), Java EE 8: Only What's New
and Professional Java EE Design Patterns. Blogger at readlearncode.com. Twitter @alextheedom

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