Geert,
I did not understand what you meant by this...
[Geert Wrtoe...
> As you see, there are quite some problems left ;-)
> but the most important point is: How are we suppose to program things like
> this?
> That is, if you're not using EJB's, but simple beans to store the database
> information.
...]
Did you mean, we cannot write database applications without using EJBs ?
Why do you feel EJBs are more scaleable ?
Please clarify...
Thanks
Kishore Raghavan
-----Original Message-----
From: A mailing list about Java Server Pages specification and reference
[mailto:[EMAIL PROTECTED]]On Behalf Of Pedro Meza
Sent: Tuesday, June 27, 2000 7:22 AM
To: [EMAIL PROTECTED]
Subject: JSP/JDBC-bean
Geert,
I believe that you made some great points. I am just beginning to learn
JSP -
JDBC/JavaBeans. You are right in stating that I did ont close the resultset
and
statement. I see those errors and others. I have not found very much on
the
internet on JDBC/JavaBean coding so I tried something and appreciate the
feedback.
The questions I have to your comments are:
How does one do connection pooling and caching ???
When displaying the results, why would vectors be useful ??? I can sort in
my
query and do not need to reference the data but only to display it.
I am not using EJB because my company does not support them ??? What are
there
advantages ??? I understand entity beans are too slow to use and resource
intensive.
Thanks,
Pedro
Geert Van Damme wrote:
> Some remarks:
>
> Your class might work well for you, but to be used as a kind of reference
> for other users, I see quite a few issues:
> - Your object is very limited in that you always retrieve all records. You
> don't provide any search capabilities or anything.
> - You don't provide insert/update capabilities
> - You're not using connection pooling and no caching.
> - You have duplicated code: 1st to get the first record and then to get
the
> other ones. Are you sure this is working???? I think you need to call
> rs.next once in order to fetch the first row.
> - You only keep the results of the last row in you instance variables. Why
> aren't you using arrays or vectors?
> - You keep the Resultset as an instance variable in your bean????
> - you're not closing the resultset.
> - you're not closing the statement.
> - worse of all: you're not closing the connection.
> - You're catching the SQLExceoption in 2 places, and you're not looking
for
> nextException.
> - you're not closing the connection in case of exception
> - you're setting autocommit to false, but you never do a commit or a
> rollback.
>
> As you see, there are quite some problems left ;-)
> but the most important point is: How are we suppose to program things like
> this?
> That is, if you're not using EJB's, but simple beans to store the database
> information.
> I have a lot of things to tell about this, too much to put in this single
> email.
> Let's discuss this in some more detail.
>
> Geert 'Darling' Van Damme
>
> > -----Original Message-----
> > From: A mailing list about Java Server Pages specification and reference
> > [mailto:[EMAIL PROTECTED]]On Behalf Of Pedro Meza
> > Sent: woensdag 21 juni 2000 21:16
> > To: [EMAIL PROTECTED]
> > Subject: JSP - JDBC/Javabean solution
> >
> >
> > Ok folks.... I just created a solution that queries an Access
> > Database. It is a
> > JSP file that uses Javabean methods to query the database and get
> > values. I would
> > like feedback on improving the design or it could be used as a
> > reference for an
> > aspiring JSP user.
> >
> > Note: I used the jdbc-odbc bridge. If one is planning on using
> > JDBC it is best to
> > use another driver.
> >
> > The table is a Document Type Table with a TYPE_ID, DOC_TYPE,
> > DOC_DESCRIPTION.
> >
> > Pedro
> >
> > =========================== JSP FILE ==============================
> > <html>
> > <body bgcolor="white">
> > <jsp:useBean id="foo" scope="session" class="checkbox.Doc_Types" />
> > <% foo.getRecords(); %>
> > <hr><center><font face="verdana"><h2>Doc Type Table</h2>
> > <form action="update_Doc_Type.jsp">
> > <TABLE border=1 cellpadding=3 cellspacing=2>
> > <TR><TD bgcolor="white"><B><font face="verdana"
color="red">Delete</TD><TD
> > bgcolor="navy"><font face="verdana" color="white">Type ID</TD><TD
> > bgcolor="navy"><font face="verdana" color="white">DOC TYPE</TD><TD
> > bgcolor="navy"><font face="verdana" color="white">DOC
> > DESCRIPTION</TD></TR>
> > <% while (foo.nextRecord() == true) { %>
> > <TR><input type="hidden" name="Doc_Type_ID"
> > value="<%=foo.getType_ID()%>">
> > <td><center><input type="checkbox" name="delete_<%=foo.getType_ID()%>"
> > value="Y"></td>
> > <TD><font face="verdana"><%= foo.getType_ID() %></TD>
> > <TD><font face="verdana"><%= foo.getDoc_Type() %></TD>
> > <TD><font face="verdana"><%= foo.getDoc_Desc() %></TD>
> > <%}%>
> > </TR>
> > </TABLE><BR><BR><BR>
> > <INPUT TYPE="Submit" VALUE="SUBMIT"> <INPUT TYPE=RESET VALUE="CLEAR">
> >
> > </form>
> > </font>
> > </body>
> > </html>
> >
> > =========================== JavaBean File
> > =================================
> > package checkbox;
> >
> > import java.io.*;
> > import java.sql.*;
> > import sun.jdbc.odbc.*;
> >
> >
> > public class Doc_Types {
> > int type_id;
> > String doc_type;
> > String doc_desc;
> > ResultSet rs;
> >
> > // Get Database Records
> > public void getRecords() {
> > String url = "jdbc:odbc:pit";
> > try {
> > Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
> > Driver driver = new sun.jdbc.odbc.JdbcOdbcDriver();
> > } catch(Exception ee) {
> > System.out.println(ee.getMessage());
> > }
> > try {
> > java.sql.Connection con =
> > DriverManager.getConnection(url,"admin", "pit");
> > con.setAutoCommit(false);
> > java.sql.Statement stmt = con.createStatement();
> > String query;
> > query = "SELECT * from DOC_TYPES";
> > rs = stmt.executeQuery(query);
> > type_id = rs.getInt("TYPE_ID");
> > doc_type= rs.getString("DOC_TYPE");
> > doc_desc= rs.getString("TYPE_DESCRIPTION");
> > } catch (SQLException e) {
> > System.err.println("SQLException: " + e.getMessage());
> > }
> > }
> > // Get the next Database record. Returns true or false if there are
more
> > public boolean nextRecord() {
> > boolean check;
> > try {
> > check=rs.next();
> > type_id = rs.getInt("TYPE_ID");
> > doc_type= rs.getString("DOC_TYPE");
> > doc_desc= rs.getString("TYPE_DESCRIPTION");
> > return check;
> > }
> > catch (SQLException e) {
> > System.err.println("SQLException: " + e.getMessage());
> > }
> > return false;
> > }
> >
> > public int getType_ID() {
> > return type_id;
> > }
> >
> > public String getDoc_Type() {
> > return doc_type;
> > }
> >
> > public String getDoc_Desc() {
> > return doc_desc;
> > }
> >
> >
> > }
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