Why result set is empty

Question

String name = request.getParameter("type");
String queryString = "SELECT * FROM Customer WHERE TYPE='Provider';";

rs = statement.executeQuery(queryString);
while(rs.next()) out.print(rs.getString(2));

prints nothing, why? I checked the DB connection but i'm connected to it successfully. What might be the problem?

whole code in jsp. I think there is a problem with whole code. What is the problem here?

<%@page import="java.sql.Statement"%>
<%@page import="java.sql.ResultSet"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.Connection"%>
 
        

        GET CUSTOMER LIST

        
        
        



         
          

        

        
        
        
        

        
        

                     
        

              
        


        


     

    

        



        
            
                
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                GET CUSTOMER LIST
MONITOR CASH FLOW
GET CUSTOMER STATE INFO
MONITOR FINANCIAL TRANSACTIONS
GET PAYMENT PLAN
         
        











    
        
        GET CUSTOMER LIST

        




        
    









 <% 




try {
/* Create string of connection url within specified format with machine name, 
port number and database name. Here machine name id localhost and 
database name is usermaster. */ 
String connectionURL = "jdbc:mysql://localhost:3306/TekirMobile"; 

// declare a connection by using Connection interface 
Connection connection = null; 

// Load JBBC driver "com.mysql.jdbc.Driver" 
Class.forName("com.mysql.jdbc.Driver").newInstance(); 

/* Create a connection by using getConnection() method that takes parameters of 
string type connection url, user name and password to connect to database. */ 
connection = DriverManager.getConnection(connectionURL, "root", "fenderpass");

 ResultSet rs = null;
 Statement statement = null;


if(request.getParameter("submit")!=null)
 {


String name = request.getParameter("type");
String queryString = "SELECT * FROM Customer WHERE TYPE='Provider'";

out.print(queryString);


rs = statement.executeQuery(queryString);
 for (int i = 1; rs.next(); i++) { 
    out.println("row=" + i + ": " + rs.getString(2));
} 


}

// check weather connection is established or not by isClosed() method 
if(!connection.isClosed())
%>

<% 
connection.close();
}
catch(Exception ex){

%>


<%
}
%>










                



    





    

        
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Nathan Hughes · Accepted Answer

Some things I would try:

Remove the semicolon at the end of the query. SQL Queries passed into statements don't need an ending semicolon.

Change the last line shown to

for (int i = 1; rs.next(); i++) { 
    out.println("row=" + i + ": " + rs.getString(2));
}

This way you can tell if there were no rows returned at all, or if all the rows returned were empty strings.

Your statement never gets initialized, trying to use it will result in a NullPointerException. It's likely you have an exception thrown that you're not seeing because it gets eaten without a trace in the catch block. Edit your catch block to display the stack trace from the exception, like this:

}
catch(Exception ex){
    ex.printStackTrace();
}

Why result set is empty

Answers (2)

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