Re: converting some VB code to Java..

From:
maya <fdr58@yahoo.com>
Newsgroups:
comp.lang.java.help
Date:
Tue, 30 May 2006 09:06:23 -0400
Message-ID:
<447c432d$0$15785$14726298@news.sunsite.dk>
I just wanted to thank you again for all your help, Bjorn.. thanks for
the db-code and servlet...:)

Bjorn Abelli wrote:

"maya" <fdr58@yahoo.com> wrote...

Bjorn Abelli wrote:

A simple Google gives plenty of sites with AJAX connected to Java:

http://tinyurl.com/pmypd

Why not from the horses mouth, Sun:

http://developers.sun.com/ajax/

Plenty of examples there... ;-)


thank you Bjorn, I HAD searched in Google, and had found some stuff (among
others sun-pg you mention above) but can't find a step-by-step java-based
tutorial like the one here..
http://www.w3schools.com/ajax/default.asp

since you seem to know about AJAX I was wondering,


Actually, I had only heard of it, but never used it, before you asked for
it... ;-)

am looking for AJAX 'docs'...


I don't think anyone "owns" the concept. That would be Adaptive Path who
coined the expression:

http://www.adaptivepath.com/publications/essays/archives/000385.php

closest thing I found is here...
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/xmlsdk/html/7924f6be-c035-411f-acd2-79de7a711b38.asp

why does XMLHTTPRequest have an "I" at the beginning here? (it's referred
to as "IXMLHTTPRequest")


Microsoft has a naming standard where interfaces "always" starts with an
"I".

That IXMLHTTPRequest is not "exactly" the same as XMLHTTPRequest, but as it
started in IE, MSDN is one source:

http://tinyurl.com/n8n7p

Other pages that explain the concepts are:

http://en.wikipedia.org/wiki/XMLHttpRequest
http://www.xulplanet.com/references/objref/XMLHttpRequest.html
http://developer.mozilla.org/en/docs/AJAX:Getting_Started
http://developer.apple.com/internet/webcontent/xmlhttpreq.html

I would like to know what all the objs are that these properties & methods
can be applied to (is XMLHttpRequest the only obj here? or are there
others? I just need to get the "big picture" here....:)

So I'd suggest you get your hands dirty with JDBC, ResultSets,
PreparedStatements, etc... ;-)


I do know how to do db-stuff w/Java, Bjorn (probably not as much as you
do, but I do know how to connect to db, insert stuff into tables, do
updates and queries, etc..) right now I just need to figure out how to do
this in java:

 response.write("<table>")
 do until rs.EOF
   for each x in rs.Fields
     response.write("<tr><td><b>" & x.name & "</b></td>")
     response.write("<td>" & x.value & "</td></tr>")
   next
   rs.MoveNext
 loop

rs.EOF?? (resultSet EndOfFile? what does this mean?)


Yes, ADO has a slightly different approach than JDBC... ;-)

Other than that, the code would look quite similar, e.g.:

  out.print("<table>");

  while (rs.next ())
  {
     for (int i = 0; i < columnCount; i++)
     {
         out.print(
             "<tr><td><b>" +
              rsMetaData.getColumnName(i+1) +
              "</b></td>");
         out.print(
             "<td>" +
             rs.getString (i+1) +
             "</td></tr>");
      }
   }

...should be corresponding to the code you extracted.

ok, no more on AJAX questions (unless it's an AJAX/Java-related
question....:), since this is not an AJAX group.. have more JS/AJAX code
questions (xmlHttp.readyState=="complete" -- what is "complete"..), I
guess I need to switch to JS ng (I guess no AJAX-ng yet..)


Yep, that's on the client side...

again, many thanks for yr help..


You're welcome.

// Bjorn A

---------------------------------
Appendix
---------------------------------
The servlet, not tested though...

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

public class AjaxDatabaseServlet extends HttpServlet
{
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
                      throws ServletException, IOException
    {
        PrintWriter out = response.getWriter();

        String sql =
           "SELECT * FROM CUSTOMERS WHERE CUSTOMERID=" +
            request.getParameter("q");

        // You might want to fix the path to the database

        String url =
            "jdbc:odbc:DRIVER={Microsoft Access Driver (*.mdb)};DBQ=" +
            "/db/northwind.mdb";

        try
        {
            DriverManager.registerDriver(
               new sun.jdbc.odbc.JdbcOdbcDriver());

            Connection conn = DriverManager.getConnection (url);
            Statement stmt = conn.createStatement ();
            ResultSet rs = stmt.executeQuery (sql);
            ResultSetMetaData rsMetaData = rs.getMetaData();

            int columnCount = rsMetaData.getColumnCount();

            out.print("<table>");

            while (rs.next ())
            {
                for (int i = 0; i < columnCount; i++)
                {
                    out.print(
                        "<tr><td><b>" +
                        rsMetaData.getColumnName(i+1) +
                        "</b></td>");
                    out.print(
                        "<td>" +
                        rs.getString (i+1) +
                        "</td></tr>");

                }
            }

            out.print("</table>");

            // cleanup...

            rs.close();
            stmt.close();
            conn.close();
        }
        catch (SQLException ex)
        {
            ex.printStackTrace(out);
        }
    }
}

/// Bjorn A

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