Re: looking for opinons regarding best practices (jdbc, resultsets, and servlet design)

From:
=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 10 Feb 2007 13:47:41 -0500
Message-ID:
<45ce134d$0$49207$14726298@news.sunsite.dk>
javerra wrote:

Im looking for an opinion regarding best practices. Recently a friend
and I were talking about how we write our code for our web
applications. I tend to keep my jdbc code with my logic in any
servlet I am writing. My friend says that this is bad practice and
that data quries should be broken out into data access objects with
methods that pass back a result set. Is he right? Is this really bad
practice or is it really just a different type of design pattern?
Love to hear everyones thoughts...

Im always doing something like this....

        try {
        Connection Conn = DriverManager.getConnection("jdbc:mysql://
sql.useractive.com/USERNAME?user=USERNAME&password=PASSWORD");

        // Do something with the Connection
        Statement Stmt = Conn.createStatement();
        ResultSet RS = Stmt.executeQuery("SELECT * from SOMETABLE");

        while (RS.next()) {
            out.println(RS.getString(1));
        }
        // Clean up
        RS.close();
        Stmt.close();
        Conn.close();

        }
        catch (SQLException E) {
}


I think there are a couple of problems with your approach:
* JDBC calls in your servlet (servlet is controller layer,
   JDBC calls belong in data access layer)
* the usage of out.println (servlet is controller layer,
   output generation belong in presentation layer)

So create a data access layer with some classes that
for data retrieval has methods to return a single object or
a collection of objects. Do not return a ResultSet, because
that is still tied to the implementation of the data access
layer.

Call that from your servlet, store it in request and forward
it to a JSP pages that displays the data. Displays the data
using a taglib not with scriptlet code.

Arne

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