import java.util.*;
import java.io.*;
import java.net.URL;
import java.net.MalformedURLException;

public class Util
{

   static public URL createURL(String name)
   {
        // Turn a URL-string or filename into a URL object
        URL url = null;
        try
        {
            url = new URL(name);
            return url;
         }
         catch (MalformedURLException ex) {;}

           // If it wasn't a URL, it must be a file...
         try
         {
             File file = new File(name);
             url = new URL("file:" + file.getAbsolutePath());
             return url;
          }
          catch (MalformedURLException ex)
          {
               System.out.println ("Malformed URL " );
               return null;
           }
 }

 public static Properties loadProperties(String fileName)
 {
      try
      {
            FileInputStream fis = new FileInputStream(fileName);
            Properties properties = new Properties();
            properties.load(fis);
            return properties;
       }
       catch(FileNotFoundException e)
       {
            System.out.println ("File not found " + fileName);
            return null;
        }
        catch(IOException e)
        {
             System.out.println ( e.getMessage());
             return null;
         }
    }
}

Listing 2

import java.util.*;
import java.sql.*;

public class DBImpl implements EmployeeQuery
  {
       private Connection connection;
       private String URL="jdbc:sybase:Tds:whitehorn-dev:6600";
       private String PROPERTIES="db.properties";
       private String DRIVER="com.sybase.jdbc.SybDriver";

       public void init()
       {
           try
          {
                Properties p = Util.loadProperties(PROPERTIES);
                Class.forName(DRIVER);
                connection = DriverManager.getConnection(URL, p);
           }
           catch (ClassNotFoundException e)
           {
                 System.out.println ("Cannot find Sybase driver ");
            }
            catch (SQLException e)
            {
                 System.out.println ("Error logging into database ");
            }
   }

  public java.util.List search(Conditions c)
  {
        String sql = "select id, lastName, firstName, " +
                          "phone, e-mail from Employee" ;
        try
        {
            Statement stmt = connection.createStatement();
            ResultSet s = stmt.executeQuery(sql);
            List employeeList = new ArrayList();
            while (s.next())
           {
               Employee emp = new Employee (s.getString("id"));
               emp.setLastName (s.getString("lastName"));
               emp.setFirstName(s.getString("firstName"));
               employeeList.add(emp);
            }
            return employeeList;
     }
     catch (SQLException e)
     {
         e.printStackTrace();
         return null;
      }
   }
 }

Listing 3

import java.util.*;
import javax.naming.*;
import javax.naming.directory.*;

public class LDAPImpl implements EmployeeQuery
 {
     private String PROPERTIES="ldap.properties";
     private DirContext ctx = null;

     public void init()
     {
       try
      {
           Properties p = Util.loadProperties(PROPERTIES);
           ctx = new InitialDirContext(p);
       }
       catch(NamingException e)
       {
            System.out.println ("Failed getting context " );
        }
     }

     public java.util.List search(Conditions c)
     {
         List employeeList = new ArrayList();

         String searchRoot = "ou=People";
         String filter = "(uid=*)";
         String[] attrIDs = {"uid", "givenname", "sn",
        "telephonenumber", "mail"};
         SearchControls ctls = new SearchControls();
         ctls.setReturningAttributes(attrIDs);

         try
         {
            NamingEnumeration list =
                   ctx.search(searchRoot, filter, ctls);

         while (list.hasMore())
         {
            SearchResult nc = (SearchResult)list.next();
           Attributes attrs = nc.getAttributes();
           Attribute attrId = (Attribute) attrs.get("uid");
           String id = (String) attrId.get();
           Employee emp = new Employee(id);

           Attribute attFN=(Attribute)attrs.get("givenname");
           String firstName=(String) attFN.get();
           emp.setFirstName(firstName);

           Attribute attLN=(Attribute)attrs.get("sn");
           String lastName=(String) attLN.get();
           emp.setLastName(lastName);

   employeeList.add(emp);
        }
        return employeeList;
   }
   catch (NamingException e)
   {
         System.out.println ( e.getMessage());
         return null;
    }
  }
}

Listing 4

<?xml version='1.0'?>
<Employees>
   <Employee id='100012' >
        <lastName>Doe</lastName>
        <firstName>John</firstName>
        <phone>212-333-1111</phone>
   </Employee>
   <Employee id='100112' >
        <lastName>Sanders</lastName>
        <firstName>Jackson</firstName>
        <phone>415-633-1111</phone>
   </Employee>
   <Employee id='77112' >
        <lastName>Yeung</lastName>
        <firstName>Mike</firstName>
        <phone>201-333-1111</phone>
   </Employee>
   <Employee id='44421' >
        <lastName>Zee</lastName>
        <firstName>Mary</firstName>
        <phone>201-333-1981</phone>
        <e-mail>zee@system.com</e-mail>
   </Employee>
   <Employee id='77198' >
        <lastName>Burn</lastName>
        <firstName>Abby</firstName>
        <phone>501-443-1981</phone>
        <e-mail>abby@system.com</e-mail>
   </Employee>
   <Employee id='087198' >
        <lastName>Kingston</lastName>
        <firstName>Steve</firstName>
        <phone>917-743-1989</phone>
        <e-mail>sking@hotmail.com</e-mail>
   </Employee>
   <Employee id='8976198' >
        <lastName>King</lastName>
        <firstName>David</firstName>
        <phone>917-443-1319</phone>
        <e-mail>king@aabbcc.com</e-mail>
   </Employee>
   <Employee id='430898' >
        <lastName>Chen</lastName>
        <firstName>Irene</firstName>
        <phone>912-243-1985</phone>
        <e-mail>ichen@hotmail.com</e-mail>
   </Employee>
   <Employee id='222222' >
        <lastName>Osaka</lastName>
        <firstName>Yosi</firstName>
        <phone>917-333-1119</phone>
        <e-mail>osaka@hotmail.com</e-mail>
   </Employee>
   </Employees>

Listing 5

import java.util.*;
import java.net.URL;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.apache.xpath.*;

public class XMLImpl implements EmployeeQuery
 {
     private String XML_FILE="employees.xml";
     private DocumentBuilder domParser;

     public void init()
     {
        try
        {
            DocumentBuilderFactory factory =
                       DocumentBuilderFactory.newInstance();
            domParser = factory.newDocumentBuilder();
         }
          catch (Exception e)
         {
               System.out.println ("Failed creating dom parser ");
               e.printStackTrace();
          }
    }
      /* Return a node from the nodelist which has name */
    private Node lookup (NodeList nl, String name)
    {
          for (int i = 0; i< nl.getLength(); i++)
         {
             Node n = nl.item(i);
             if (n.getNodeName().equals(name))
                    return n;
          }
          return null;
     }

public java.util.List search(Conditions c)
 {
     try
    {
          URL cfgURL = Util.createURL(XML_FILE);
          Document d = domParser.parse(cfgURL.toString());
          String xpath = "//Employee";
          List employeeList = new ArrayList();
          NodeList nl = XPathAPI.selectNodeList(d, xpath );
          for (int i = 0; i< nl.getLength(); i++)
          {
            Node n = nl.item(i);

            // id is an attribute
            Node nm = n.getAttributes().getNamedItem("id");
            Employee emp = new Employee(nm.getNodeValue());

            // Other fields are elements
            NodeList childNodes = n.getChildNodes();
            Node lname = lookup (childNodes, "lastName");
     String ln = lname.getFirstChild().getNodeValue();
            emp.setLastName(ln);
     Node fname = lookup (childNodes, "firstName");
     String fn = fname.getFirstChild().getNodeValue();
     emp.setFirstName(fn);
     employeeList.add (emp);
            }
   return employeeList;
   }
   catch (Exception e)
   {
          e.printStackTrace();
          return null;
    }

  }
}