Exemplo

import javax.sql.*;
import javax.servlet.*;
import java.util.HashTable;
import java.io.IOException;

public class ClassA extends HttpServlet {

public void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
Connection c = null;
DataSource ds = null;
PreparedStatement statement = null;
ResultSet result = null;
try {
java.util.Hashtable env = new java.util.Hashtable();
env.put (Context.INITIAL_CONTEXT_FACTORY, "com.ibm.ejs.ns.jndi.CNInitialContextFactory");
Context ctx = new InitialContext (env);
ds = (DataSource)ctx.lookup("jdbc/SAMPLE");
ctx.close();
c = ds.getConnection("db2admin", "db2admin");
stmt = c.prepareStatement("select * from sample.name");
result = stmt.executeQuery();
}
finally {
}
}
}

Solução

javax.sql.DataSource deve ser adquirido uma vez e ser reutilizado sempre que necessário.

import javax.sql.*;
import javax.servlet.*;
import java.util.HashTable;
public class ClassA extends HttpServlet {

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, "com.ibm.ejs.ns.jndi.CNInitialContextFactory");
ctx = new InitialContext (env);
ds = (DataSource)ctx.lookup("jdbc/SAMPLE");
ctx.close();
}
catch(Exception es) {
es.printStackTrace();
}
}
}