sorting in bean objects

[payal Jain]

Hi i have a bean class objects which consist of Name ,date,Location etc. and i display them on jsp under the heading links of NAME,DATE,LOCATION now when the user clicks on the NAME it should disply the data in descending order of Name.... how to do that please help me..

[Bear Bibeault]

Where's the data coming from? If a database, it's best to have the DB do the sorting. If that's not possible, then the collection can be sorted using any of the bazillion sorting algorithms available.

[payal Jain]

can you give me any Link to or any example of this algorithm

[Bear Bibeault]

I'm sure that you can type "sorting java collections" into google as well as I can.

[Chandra Bhatt]

Hi Payal,


You might be looking something similar to below:

   
 
/*
 * Customer.java
 *
 * Created on September 11, 2008, 4:57 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */
 
package com.aol.beans;
 

/**
 *
 * @author Chandra
 */
 
public class Customer implements Comparable{
    private String name; 
    private String date; 
    private String location;
    
    public Customer() {
    } 
    
    public Customer(String name, String date, String location) {
        this.name = name;
        this.date = date;
        this.location = location;
    } 
    
    public String getLocation() {
        return location;
    }
 
    public String getDate() {
        return date;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public void setLocation(String location) {
        this.location = location;
    }
 
    public void setDate(String date) {
        this.date = date;
    }
 
    public String getName() {
        return name;
    }
        
    /** Creates a new instance of Customer */
 
    public int compareTo(Object c1) {
        Customer cus=null;
        if(c1 instanceof Customer) {
             cus = (Customer)c1;
        }
        return name.compareTo(cus.getName());
    }
    
    public String toString() {
        return "Name: " + name + "\n" +
               "Date: " + date  + "\n" +
               "Location: " + location + "\n"; 
    }
}
 

    
 
/*
 * Utility.java
 *
 * Created on September 11, 2008, 5:02 AM
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */
 
package com.aol.beans;
 
 
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
 
/**
 *
 * @author Chandra
 */
 
public class Utility {
    
    /** Creates a new instance of Utility */
    public Utility() {
    }
   
    public static List<Customer> getCustomersSortedByName(List<Customer> customers) {
        Collections.sort(customers);
        return customers;
    }
    
    public static List<Customer> getCustomersSortedByDate(List<Customer> customers) {
        Collections.sort(customers,new Comparator<Customer>() {
            public int compare(Customer c1, Customer c2) {
               return c1.getDate().compareTo(c2.getDate());
            }            
        });
        return customers;
    }
    
    public static List<Customer> getCustomersSortedByLocation(List<Customer> customers) {
        Collections.sort(customers,new Comparator<Customer>() {
            public int compare(Customer c1, Customer c2) {
               return c1.getLocation().compareTo(c2.getLocation());
            }
        });
        return customers;
    }
}

    
/*
 * CustomerServlet.java
 *
 * Created on September 11, 2008, 5:29 AM
 */
 
package com.aol.beans;
 
import java.io.*;
import java.net.*;
import java.util.ArrayList;
 
import javax.servlet.*;
import javax.servlet.http.*;
 
/**
 *
 * @author Chandra
 * @version
 */
public class CustomerServlet extends HttpServlet {
    
    /** Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        String operation = request.getParameter("op");
        if(operation==null) {
           operation=1;
        }
        Customer cust1 = new Customer("Raol","20-05-2001","New Delhi");
        Customer cust3 = new Customer("Amit","10-09-2008","Bangalore");
        Customer cust2 = new Customer("Sumit","09-08-2008","Chennai");       
        
        ArrayList custList = new ArrayList();
        custList.add(cust1);
        custList.add(cust2);
        custList.add(cust3);
        
        if(operation.equals("1")) { //sort by name
            Utility.getCustomersSortedByName(custList);
        }else if(operation.equals("2")) { //sort by date
            Utility.getCustomersSortedByDate(custList);
        }else if(operation.equals("3")) { //sort by location
            Utility.getCustomersSortedByLocation(custList);
        }
        
        request.setAttribute("custList",custList);
        RequestDispatcher dispatcher = request.getRequestDispatcher("CustomerTestJSP.jsp");
        dispatcher.forward(request,response);
    }
    
    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }
    
    /** Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }
    
    /** Returns a short description of the servlet.
     */
    public String getServletInfo() {
        return "Short description";
    }
    // </editor-fold>
}
 

    
<%@page contentType="text/html"%>
<%@page pageEncoding="UTF-8"%>
 
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">
 
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
    <%@page  import="com.aol.beans.*,java.util.*"%>
    
   <form action = "/Minerva/CustomerServlet" method="get">
   <select name="op">
       <option value="1"> Sort By Name
       <option value="2"> Sort By Date
       <option value="3"> Sort By Location
   </select>
   <br>
   <% ArrayList custList =(ArrayList) request.getAttribute("custList");
   Iterator iter = custList.iterator();
   while(iter.hasNext()) {
       Customer c1 =(Customer) iter.next();
       out.println(c1.getName() + "     " + c1.getDate() + "    " + c1.getLocation() + "<br>");
   }
   %>        
   <input type ="submit" value="Sort">
   </form>
    </body>
</html>
 

[ September 10, 2008: Message edited by: Chandra Bhatt ]

[payal Jain]

Thanks for the help...
I was looking for this sorting only.