Reusing Database Objects
In the introduction, we mentioned that the servlet life cycle allows
for extremely fast database access. After you’ve used JDBC for
a short time, it will become evident that the major performance
bottleneck often comes right at the beginning, when you are opening a
database connection. This is rarely a problem for most applications
and applets because they can afford a few seconds to create a
Connection
that is used for the life of the
program.
With servlets this bottleneck is more
serious because we are creating and tearing down a new
Connection
for every page request. Luckily, the
servlet life cycle allows us to reuse the same connection for
multiple requests, even concurrent requests, as
Connection
objects are required to be thread safe.
Reusing Database Connections
A servlet can create one or more
Connection
objects in its
init()
method and reuse them in its
service()
, doGet()
, and
doPost()
methods. To demonstrate, Example 9.4 shows the phone lookup servlet rewritten to
create its Connection
object in advance. It also
uses the HtmlSQLResult
class from Example 9.3 to display the results. Note that this servlet
uses the Sybase JDBC driver.
Example 9-4. An improved directory servlet
import java.io.*; import java.sql.*; import javax.servlet.*; import javax.servlet.http.*; public class DBPhoneLookupReuse extends HttpServlet { private Connection con = null; public void init(ServletConfig config) throws ServletException { super.init(config); try { // Load (and ...
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