SERVLET.DSLV

Reuse datasources for JDBC connections

Description

This rule flags code that should reuse datasources for JDBC connections, but does not.

A javax.sql.DataSource is obtained from WebSphere Application Server through a JNDI naming lookup. Avoid the overhead of acquiring a javax.sql.DataSource for each SQL access. This is an expensive operation that will severely impact the performance and scalability of the application.

Example

 package SERVLET;
 
 import javax.servlet.*;
 import javax.servlet.http.*;
 import javax.sql.*;
 import javax.naming.Context;
 import javax.naming.InitialContext;
 
 public class DSLV extends HttpServlet {
     public void doGet () throws ServletException {
         DataSource ds = null;    // violation
         try {
             java.util.Hashtable env = new java.util.Hashtable ();
             env.put (Context.INITIAL_CONTEXT_FACTORY, "jndi.
CNInitialContext");
             Context ctx = new InitialContext (env);
             ds = (DataSource)ctx.lookup ("jdbc/SAMPLE");
             ctx.close ();
         } catch (Exception e) {
             e.printStackTrace ();
         }
     }
 }

Repair

The servlet should acquire the javax.sql.DataSource in the Servlet.init () method (or some other thread-safe method) and maintain it in a common location for reuse.

 class Better extends HttpServlet {
     // caching the DataSource
     private DataSource ds = null;
     public void init (ServletConfig config) throws ServletException 
{
         super.init (config);
         Context ctx = null;
         try {
             java.util.Hashtable env = new java.util.Hashtable ();
             env.put (Context.INITIAL_CONTEXT_FACTORY, 
"jndi.CNInitialContext");
             ctx = new InitialContext (env);
             ds = (DataSource)ctx.lookup ("jdbc/SAMPLE");
             ctx.close ();
         } catch (Exception e) {
             e.printStackTrace ();
         }
     }
 }

Reference

IBM WebSphere Application Server Standard and Advanced Editions, Harvey W. Gunther.

http://www-4.ibm.com/software/webservers/appserv/ws_bestpractices.pdf