Weblog

Listing 4: ShowBlog.java

/* A servlet to display the contents of our Weblog ("blog").

   The Weblog is stored in a PostgreSQL database table.
 */

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

public class ShowBlog 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://localhost/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();

	out.println("<HTML><Head><Title>Weblog</Title></Head>");
	out.println("<Body><H1>Weblog</H1>");
	    
	try
	    {
		// Declare our statement
		Statement statement = con.createStatement();
			
			String query = "SELECT entry_date, entry_headline, ";
			query +=       "       entry_text ";
			query +=       "FROM   BlogEntries ";
			query +=       "ORDER BY entry_date DESC ";
	    
			// Perform the query
			ResultSet rs = statement.executeQuery(query);
		    
			out.println("<table>");
		    

			// Iterate through each row of rs
			while (rs.next())
			    {
				String entry_date = rs.getString("entry_date");
				String entry_headline = 
				    rs.getString("entry_headline");
				String entry_text = 
				    rs.getString("entry_text");

				out.println("<tr>" + 
					    "<td>" + entry_date + "</td>" +
					    "<td>" + entry_headline + "</td>" +
					    "<td>" + entry_text + "</td>" +
					    "</tr>");
			    }
		    
			out.println("</table>");

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

    }
}