Filtering Result Sets based on selectable links (a href:)

Hello Forum,

Working on a class project... I have an include (header jsp) and a main view with a full result set. There are five category links added in the header jsp that when selected, the resultset in the main view should filter based on what's selected. However, I do not know how to drive a different filter or resultSet based on clicking an html link.

I can create 5 seperate action servlets for each seperate link and re-display the results, but I do not think that is the best approach.

Can someone help me with the best solution?

Here is the code:
The Include with Links:

<jsp:include page = "Template.jsp" />

}

#warning {
        padding-top: 0px;
        font-family: Arial;
        text-align: center;
        color: #6E899C;

}

body{
        font-family: Arial;
        font-size: 14px;
        color: #5E702F;

}

h3{
        color: red;
}

#leftAdmin {
    float: left;
    color: chocolate;
    border: solid #8BA545;
    border-width: 1px;
}
</style>

<div id="left">
    <h3><u>Product Categories</u></h3>

<a name="" href="ProductMain">Baby Care</a>
    
    <a name="" href="ProductMain">Baby Clothes</a>
    
    <a name="" href="ProductMain">Baby Bath</a>
    
    <a name="" href="ProductMain">Baby Feeding</a>
    
    <a name="" href="ProductMain">Health and Safety</a>
    
    <a name="" href="ProductMain">Just For Mom</a>

<div id="leftAdmin">
    <a href="NewProductForward">Insert New Product <br>
        (admin only)</a>
</div>

</div>

<jsp:include page = "/jsp/Right.jsp" />

</div>

Here is the main view with the ResultSet displayed that should filter based on the category selected

<jsp:include page = "Includes/mainTop.jsp" />
<jsp:useBean id="prod" scope="session" class="edu.virginia.Datasource.ProductDB" />
<%@page import="java.util.List"%>
<style type="text/css">
    /*Center Div Tag:  Overide format from css */

#poamTable {
        table-layout: auto;
        text-align:  center;
        font-family: Arial;
        font-size: 10px;
    }

#productTable td {
        border: 1px solid #8BA545;
    }

#poamTable textarea{
        font-family: cursive;
        font-size: 10px;
    }

</style>

<div id="center">
    <div id="form">

<table id="productTable"width="auto" cellpadding="1" >
            <thead>
                <tr>
                    <th colspan="10"><h2> Products <br /><br /></h2></th>

</tr>
            </thead>
            <%
                        List prodList = (List) session.getAttribute("prodList");
                        int size = prodList.size();

%>

<tbody>
                <tr>
                    <td><b>Name</b></td>
                    <td><b>sku#</b></td>
                    <td><b>Category</b></td>
                </tr>
                <%

for (int i = 0; i < size; i += 9) {
                                String sku = (String) prodList.get(i);
                                String category = (String) prodList.get(i + 1);
                                String description = (String) prodList.get(i + 2);
                                String name = (String) prodList.get(i + 3);
                                String price = (String) prodList.get(i + 4);
                                String inventoryLevel = (String) prodList.get(i + 5);
                                String brand = (String) prodList.get(i + 6);
                                String gender = (String) prodList.get(i + 7);
                                String prodSize = (String) prodList.get(i + 8);

%>
                <tr>
                    <td><%=name%></td>
                    <td><%=sku%></td>
                    <td><%=category%></td>
                </tr>

</tbody>
            <%}%>

</table>
    </div>
    <div id="warning"

</div>

<jsp:include page = "Includes/mainBottom.jsp" />

Servlet Code:

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package edu.virginia.ProductServlet;

import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.*;

//Import for Security Check
import javax.servlet.http.HttpSession;
import edu.virginia.Datasource.*;
import java.util.List;

public class ProductMain extends HttpServlet {

@Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //Forwards any doGet to doPost for better handling
        doPost(request, response);
    }

@Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

RequestDispatcher dispatcher = null;
        HttpSession session = request.getSession();
        ProductDB pdata = new ProductDB();
        String query = null;

query = "SELECT * FROM Product;";

List prodList = pdata.retrieveProducts(query);

session.setAttribute("prodList", prodList);

dispatcher = request.getRequestDispatcher("/jsp/Main.jsp");
        dispatcher.forward(request, response);

}
}

Helper Class (DAO):

public List retrieveProducts(String query) {
        List<String> products = new ArrayList<String>();

ResultSet rs = null;
        try {

con = dbcon.SimpleConnection();

stmt = con.createStatement();

//query = "SELECT * FROM Product;";
            System.out.println(query);

rs = stmt.executeQuery(query);

//Add result into an arraylist and release the resultset
            while (rs.next()){
                    products.add(rs.getString(1));
                    products.add(rs.getString(2));
                    products.add(rs.getString(3));
                    products.add(rs.getString(4));
                    products.add(rs.getString(5));
                    products.add(rs.getString(6));
                    products.add(rs.getString(7));
                    products.add(rs.getString(8));
                    products.add(rs.getString(9));

}
            //Return the array
            
        } catch (SQLException sqe) {
            System.out.println(sqe.getMessage());
        } finally {
            close.closeAll();
        }

return products;
    }

Did you know you can pass parameters in a URL. For example:
/MyServlet?category=1 or /MyServlet?category=feeding

Then in your servlet, you can filter by that category. Either with a PreparedStatement (JDBC) or an API on ProductDB that takes a where clause or even looping through the list afterwards if the first two can't be used.

Also, in the JSP< take a look at JSTL/EL. Scriptlets are an old fashioned way of putting Java code in JSPs and has fallen out of use. Since all you are doing is looping through a list, JSTLs for loop is perfect.

Thank you, works!

Anyway to hide the parameter in the url header when clicked? I try to disguise all if possible.

I need to learn JSTL for this class, just having a hard time getting there. I appreciate your time.
Ron

Ron Ingram wrote:Anyway to hide the parameter in the url header when clicked? I try to disguise all if possible.

Why? That's completely counter to how HTTP and the Web are supposed to work.

Well, I don't want to allow anyone to navigate throughout a webapp by changing or messing around with the url. Would like to constrain them to navigate through the application only if possible. Also, I believe there is some security concerns by changing the url. I'm still a newbie though....

With all due respect, that is a bit of a newbie attitude. URLs are the heart of the web. The way to secure a web site is to make sure that no matter what the URL is that nothing can be comprised, not to try and mess around with the URL.

And aside from ensuring that no sensitive data appears unencrypted in a URL (or anywhere on the client), no real security is afforded by trying to obfuscate URLs.

Bear, thats fine. I will adopt that approach, thanks again!

The trend is definitely towards what has become known as "friendly" or "RESTful" URLs. Another way of putting it is that the trend is towards semantic URLs -- the exact opposite of obfuscated URLs.

This is the way that the inventors of HTTP intended it be used in the first place, but the Web just sort of lost its way somewhere along the way. Now the trend is to find its way back.