" + "DailySaying: Error" + "

4783l3

Listing 3: DailySaying.java, which pulls today's saying from a
PostgreSQL database and displays it in our XMLC document.

import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

// Bring in the DOM classes which come with Enhydra
import org.w3c.dom.html.*;

// Bring in the "saying" XMLC class
import il.co.lerner.*;

public class DailySaying extends HttpServlet 
{

    // Keep the connection common to the entire instance
    private Connection con;
				
    // Our "init" method sets up a database connection
    public void init(ServletConfig config) throws ServletException
    {
	// Some private variables for logging into the database
	String loginJdbc = "org.postgresql.Driver";
	String loginUser = "reuven";
	String loginPasswd = "";
	String loginUrl = "jdbc:postgresql://127.0.0.1/atf";

	// Load the PostgreSQL driver
	try 
	    {
		Class.forName(loginJdbc);
		con = 
		    DriverManager.getConnection(loginUrl, 
						loginUser, loginPasswd);
	    }
	catch (ClassNotFoundException e)
	    {
		throw new
		    UnavailableException("Cannot load the PostgreSQL driver: "
					 + e);
	    }
	catch (SQLException e)
	    {
		throw new
		    UnavailableException("Error connecting to PostgreSQL: "
					 + e);
	    }
    }

    // Our "doGet" method returns an error message indicating
    // that only "POST" is acceptable.

    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException
    {
	// Set the MIME content type for the response
	response.setContentType("text/html");

        // Get the output stream to STDOUT
        PrintWriter out = response.getWriter();

	try
	    {
		// Declare our statement
		Statement statement = con.createStatement();
			
		// Declare and initialize the saying text
		String saying_text = "";

		// Make sure that only one thread handles this
		// statement at a time
		synchronized (statement) 
		    {
			String query = "SELECT saying ";
			query += "FROM DailySayings ";
			query += "WHERE date = CURRENT_DATE ";
			
			// Perform the query
			ResultSet rs = statement.executeQuery(query);
		    
			// Iterate through each row of rs (which should
			// only be one iteration, since date is unique!)
			while (rs.next())
			    {
				saying_text = rs.getString("saying");
			    }
		    }

		// Create an instance of our "saying" page object.
		saying mysaying = new saying();

		// Change the text in our "saying" paragraph.
		mysaying.setTextSaying(saying_text);

		// Display the results
		out.println(mysaying.toDocument());

	    }
	catch(Exception e)
	    {
		out.println("<HTML>" +
			    "<Head><Title>" +
			    "DailySaying: Error" +
			    "</Title></Head>\n<Body>" +
			    "<P>SQL error in doGet: " +
			    e + "</P></Body></HTML>");
		return;
	    }

    }
}