ricky
Posts: 8
Nickname: ricky30000
Registered: Jul, 2003
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Re: How i put an applet on the web, which is communicate with a database
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Posted: Sep 23, 2004 10:38 AM
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You need to use a three tier architecture. Like an applet connecting to a servlet, which then connects to the database and parses it back through the servlet.
The Search Servlet
/* This servlet retrieves the parameters from the applet in order to carry out the search. The variables
* make, model, min Price and max price are put into a SQL string. When the query is executed and put
* into a ResultSet, and all the information that is needed like description, audio URL, image URL and
* video URL. The information is put into vectors and then are written out to the applet.
*/
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.net.*;
import java.io.Serializable;
import java.applet.*;
import javax.swing.*;
import java.awt.*;
public class searchDatabaseServlet extends HttpServlet
{
private ResultSet resCars;
private Vector textDescription, listString, playAudio, addImage, playVideo;
public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
//declaration of variables which are initialized to null
resCars = null;
Connection con = null;
Statement stmt = null;
String searchString = null;
String makeSearch = null;
String modelSearch = null;
String minSearch = null;
String maxSearch = null;
try
{
//load the Sun driver
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
//get a connection to the database
con =DriverManager.getConnection("jdbc:odbc:searchengine");
//create a statement object
stmt = con.createStatement();
//request the parameters from the applet
makeSearch = req.getParameter("make");
modelSearch = req.getParameter("model");
minSearch = req.getParameter("minprice");
maxSearch = req.getParameter("maxprice");
//The search SQL query
searchString = "SELECT * FROM cars WHERE make = '" + makeSearch + "' AND model = '" + modelSearch + "' AND price >= " + minSearch + " AND price <= " + maxSearch + "";
//A different SQL query is used if the model parameter is equal to the String Any
if(modelSearch.equals("Any"))
{
searchString = "SELECT * FROM cars WHERE make = '" + makeSearch + "' AND model AND price >= " + minSearch + " AND price <= " + maxSearch + "";
}
//execute an SQL query, get a ReultSet
resCars = stmt.executeQuery(searchString);
//create all the vectors
textDescription = new Vector();
listString = new Vector();
textDescription = new Vector();
playAudio = new Vector();
addImage = new Vector();
playVideo = new Vector();
/*Search through the ResultSet and retrieve the strings from the database that is
*needed.
*/
while(resCars.next())
{
listString.addElement("Car: " + resCars.getString(1) + " Model: " + resCars.getString(2) + " Registration Year: " + resCars.getString(6) + " Price: " + resCars.getString(3));
textDescription.addElement(resCars.getString(5));
playAudio.addElement(resCars.getString(7));
addImage.addElement(resCars.getString(8));
playVideo.addElement(resCars.getString(9));
}
//Create an ObjectOutputStream to write out all the vectors to the applet.
ObjectOutputStream outPut = new ObjectOutputStream(res.getOutputStream());
outPut.flush();
outPut.writeObject(listString);
outPut.flush();
outPut.writeObject(textDescription);
outPut.flush();
outPut.writeObject(playAudio);
outPut.flush();
outPut.writeObject(addImage);
outPut.flush();
outPut.writeObject(playVideo);
outPut.close();
}
catch(ClassNotFoundException e) {
System.out.println("Couldn't load database driver: " + e.getMessage());
}
catch(SQLException e) {
System.out.println("SQLException caught: " + e.getMessage());
}
finally {
//always close the database connection
try
{
if (con != null) con.close();
}
catch (SQLException ignored) { }
}
}//end of doGet
}//end of Http Servlet
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