如何使用jsp从表中检索数据？

Question

I am Trying to retrieve data from questions table but this below code is not showing an output.

index.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@page import="java.sql.*" %>


<%  
Connection con = null;  
Statement st   = null;
ResultSet rs   = null;

try{
Class.forName("com.mysql.cj.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://127.0.0.1/users","root", "1234");
String qry = "SELECT * FROM questions";
rs = st.executeQuery(qry);

while(rs.next()){
   out.println("Email :" + rs.getString(2) + "<br>");
   out.println("Title :" + rs.getString(3) + "<br>");
   out.println("Description :" + rs.getString(4) +"<br>");
}
}
catch(Exception ex){}
%>    

Answer 1

What is out.println? that's not how you output using scriptlets. it should look something like this:

        while(rs.next()){
           %>
           <%="Email :" + rs.getString(2) + "<br>"%>
           <%="Title :" + rs.getString(3) + "<br>"%>
           <%="Description :" + rs.getString(4) +"<br>"%>
           <%
        }

And most people would say to not use scriptlets to begin with.

If that doesn't fix the problem, you might have caught an exception. Try and output the exception like this:

   catch(Exception ex){%><%=ex.toString()%><%}

It looks like you have a java.lang.NullPointerException, so you have to figure out which object you are trying to use is null. Looking at your code, it looks like you never initialize your Statement st . Try adding in st = con.createStatement() after the line that says con = DriverManager.getConnection("jdbc:mysql://127.0.0.1/users","root", "1234");