And I forgot few things.
- Sometimes (depending on the complexity) I put the lookup methods in a
separate class. (like StaffSearcher).
- I also create another object as an interface between servlets/JSP and the
bean to handle the communication between a posted form and the bean.
This is because I don't want to import javax.servlet. and use these specific
servlet classes in these beans.
I can use the updater in my servlets and JSP like
StaffUpdater updater = new StaffUpdater();
updater.update(request,response);
Geert 'Darling' Van Damme
> -----Original Message-----
> From: A mailing list about Java Server Pages specification and reference
> [mailto:[EMAIL PROTECTED]]On Behalf Of Geert Van Damme
> Sent: woensdag 28 juni 2000 21:35
> To: [EMAIL PROTECTED]
> Subject: Re: JSP/JDBC-bean - Geert
>
>
> nono, not at all. You understood this wrong.
> I'm not using EJB's myself, but with EJB's there's a very detailed outline
> on how you're supposed to create them and what methods are needed.
> If you use simple classes/beans to do the db work, there isn't any guide.
> So everyone has to re-invent what's the best way to code these. And I've
> seen quite some bad solutions.
>
> I used mainly 2 approaches.
> * the first one is a generic wrapper class around a SQL statement. The
> details (select statement, column list, data types, whether it's
> updateable
> or not, connection name...) are stored in a configuration file.
> This allows me to do easy reporting and direct updating/inserting in the
> database. The data are cached in memory so that I can close the connection
> after retrieving the data.
> This is more or less like a CachedRowSet.
>
> * On other occasions I create beans that map the specific
> business objects.
> But especially here it's not clear how we 're supposed to do this.
> I mostly create:
> - a constructor without params (required for beans) and that allows me to
> insert new objects in the db.
> - a constructor that takes the primary key
> - sometimes some other lookup constructors, like with a name.
> - a load method
> - a save method (that inserts or saves depending on whether the load
> function was already called)
> - sometimes a delete method (but I don't delete often from a database)
> - get and set methods for the main data fields
> - a generic get and set method for other data fields like
> String getValue(String field) and
> void setValue(String field, String value)
> - Static lookup methods that return an instance, an array of
> instances or an
> array of keys.
>
> I would like to put this way of working in some sort of light
> framework with
> interfaces, utility classes and parts of the code I keep
> rewriting in all my
> classes.
> I really need to do some good refactoring here.
> Are there any suggestions? remarks on my outline above, comments,
> alternatives....
>
> Geert 'Darling' Van Damme
>
>
>
>
>
>
>
> > -----Original Message-----
> > From: A mailing list about Java Server Pages specification and reference
> > [mailto:[EMAIL PROTECTED]]On Behalf Of Kishore Raghavan
> > Sent: woensdag 28 juni 2000 20:51
> > To: [EMAIL PROTECTED]
> > Subject: Re: JSP/JDBC-bean - Geert
> >
> >
> > 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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> > Some relevant FAQs on JSP/Servlets can be found at:
> >
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> >
>
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>
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