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How to display retrivied users from the Datase into Drop-down menu using servlet+JSP(JSTL)

Vas Miriyala

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posted 15 years ago

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Hi
Here what I am going to do is I want to display existign users in database in Drop-down menu, for this i have written class file to connect to database ,one more class file to perform database queries and one servlet for calling method which i have retrived an stored in arraList, and then i have written jsp(using JSTL) file to display the users in drop-down menu,but my JSP file is not showing any user and these are the code i have written
Database1.java

package ims;
import java.sql.*;
public class Database1 {
final String server="localhost:3306";
final String user="root";
final String  password="miriyala";
final String database="NEWIMS";
public Connection con=null;
public ResultSet rs=null;
public Statement stmt=null;

public  Database1()
	{
			try{
					Class.forName("com.mysql.jdbc.Driver");
					con=DriverManager.getConnection("jdbc:mysql://"+server+"/"+database,user,password);
					stmt=con.createStatement();

}
			catch(Exception ex)
	 		   {
					System.out.println(ex.toString());
			   }

}
public void executeUp(String query) throws Exception
{
         	         stmt.executeUpdate(query);
         	         con.close();
}
}

class file to preform database queries adminClass1.java here i am giving only what methos i called from the servlet
[code]
public ArrayList<String> displayusers()
{
       Database1 db = new Database1();
    ArrayList<String> al = new ArrayList<String>();
      try{
        String str = "select username from user_details";
                db.rs=db.stmt.executeQuery(str);
        while(db.rs.next())
        {
           al.add(db.rs.getString("username"));
            //al.add("username");  
            System.out.println("got the users");  
             for(Iterator iter = al.iterator(); iter.hasNext();)
    {
        System.out.println((String)(iter.next()));
    } 
                       
        }
    }
        catch(Exception e) {
            System.out.println(e);
            System.out.println("error");
        }
   
return al;    
}

comboboxServlet.java

package ims;
//import ims.*;
import java.util.*;
import java.io.*;
import java.net.*;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class comboServlet extends HttpServlet {
    @Override
           public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
    //    processRequest(request, response);
     HttpSession session = request.getSession(true);
        ArrayList<String> list = new ArrayList<String>();       
        PrintWriter out = response.getWriter();    
    adminClass1 ac = new adminClass1();
    list=  ac.displayusers();
    int i = list.size();
    //list.add("username");
    System.out.println("size =" + i);
  
        if(i != 0)
    {
      //  list.add("username");
        System.out.println("added users to the Arraylist");
    }
    else
    {
        System.out.println("list is empty");
    } 
   
    list = (ArrayList)session.getAttribute("username");
    RequestDispatcher dispatcher = request.getRequestDispatcher("user.jsp");
      if (dispatcher != null){
        dispatcher.forward(request, response);  
    }
}
}

and finally user.jsp

guys please help me and thanks in advance

Albareto McKenzie

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posted 15 years ago

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This problem is not the same as this other? https://coderanch.com/t/471351/JSP/java/JSTL-Servlet-beans

What problem do you have? What are you doing in line 39 in the Servlet? You are overwritting the ArrayList with the session element!

Albareto McKenzie

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posted 15 years ago

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And this piece of code in jsp:

is very wrong, is not XML compliance, and the forEach is very strange, please look at the documentation for contructing a forEach, userREsult does not have any other reference in the code posted... please, clarify yourself before posting code

Vas Miriyala

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posted 15 years ago

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thanks for you reply,My porblem is JSP file is not showing users in the drop-dwon menu and in line 39 I am retriving arraylist object from the session object and correct me if i am wrong,I tried with commenting line 39 but same problem

Albareto McKenzie

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posted 15 years ago

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Look to this info for building EL elements:

http://java.sun.com/j2ee/1.4/docs/tutorial/doc/JSPIntro7.html

You cannot access anything you want in your JSP, you have to access scoped attributes, declared variables or implicit objects

Albareto McKenzie

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posted 15 years ago

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srinivas miriyala wrote:thanks for you reply,My porblem is JSP file is not showing users in the drop-dwon menu and in line 39 I am retriving arraylist object from the session object and correct me if i am wrong,I tried with commenting line 39 but same problem

But do you have that ArrayList in the Session? Have you set it before? Do you have your ArrayList in any scope to be retrieved by the JSP? You have to set it in the request or in session (better in request) as an attribute in the Servlet

then in your JSP you access it:

But please, first of all look at the documentation for creating JSPs with JSTL and EL.

Vas Miriyala

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posted 15 years ago

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well thanks for you help

Consider Paul's rocket mass heater.