How do I set miminum # of connections for pool with Oracle and Tomcat?

Question

Hi,
I can't seem to find any attribute to initialize the number of connections for my connection pool. Here is my current context.xml file under my /App1 directory:
<Context path="/App1" docBase="App1"
debug="5" reloadable="true" crossContext="true">
<Resource name="App1ConnectionPool" auth="Container"
type="oracle.jdbc.pool.OracleDataSource"
driverClassName="oracle.jdbc.driver.OracleDriver"
factory="oracle.jdbc.pool.OracleDataSourceFactory"
url="jdbc:oracle:thin:@127.0.0.1:1521:oddjob"
user="app1" password="app1" />
</Context>
I've been googling and reading forums, but haven't found a way to establish the minimum number of connections. I've tried all sorts of parameters like InitialLimit, MinLimit, MinActive, etc, with no success.
Here is some sample code that I am testing:
package web;
import oracle.jdbc.pool.OracleDataSource;
import oracle.jdbc.OracleConnection;
import javax.naming.*;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;
public class ConnectionPool {
String message = "Not Connected";
public void init() {
OracleConnection conn = null;
ResultSet rst = null;
Statement stmt = null;
try {
Context initContext = new InitialContext();
Context envContext = (Context) initContext.lookup("java:/comp/env");
OracleDataSource ds = (OracleDataSource) envContext.lookup("App1ConnectionPool");
message = "Here.";
     String user = ds.getUser();
if (envContext == null)
throw new Exception("Error: No Context");
if (ds == null)
throw new Exception("Error: No DataSource");
if (ds != null) {
message = "Trying to connect...";
conn = (OracleConnection) ds.getConnection();
Properties prop = new Properties();
prop.put("PROXY_USER_NAME", "adavey/xxx");
if (conn != null) {
message = "Got Connection " + conn.toString() + ", ";
          conn.openProxySession(OracleConnection.PROXYTYPE_USER_NAME,prop);
stmt = conn.createStatement();
rst = stmt.executeQuery("SELECT username, server from v$session where username is not null");
while (rst.next()) {
message = "DS User: " + user + "; DB User: " + rst.getString(1) + "; Server: " + rst.getString(2);
rst.close();
rst = null;
stmt.close();
stmt = null;
conn.close(); // Return to connection pool
conn = null; // Make sure we don't close it twice
} catch (Exception e) {
e.printStackTrace();
} finally {
// Always make sure result sets and statements are closed,
// and the connection is returned to the pool
if (rst != null) {
try {
rst.close();
} catch (SQLException e) {
rst = null;
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
stmt = null;
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
conn = null;
public String getMessage() {
return message;
I'm using a utility to repeatedly call a JSP page that uses this class and displays the message variable. This utility allows me to specify the number of concurrent web requests and an overall number of requests to try. While that is running, I look at V$SESSION in Oracle and occassionaly, I will see a brief entry for app1 or adavey depending on the timing of my query and how far along the code has processed in this example. So it seems that I am only using one connection at a time and not a true connection pool.
Is it possible that I need to use the oci driver instead of the thin driver? I've looked at the javadoc for oci and the OCIConnectionPool has a setPoolConfig method to set initial, min and max connections. However, it appears that this can only be set via Java code and not as a parameter in my context.xml resource file. If I have to set it each time I get a database connection, it seems like it sort of defeats the purpose of having Tomcat maintain the connection pool for me and that I need to implement my own connection pool. I'm a newbie to this technology so I really don't want to go this route.
Any advice on setting up a proper connection pool that works with Tomcat and Oracle proxy sessions would be greatly appreciated.
Thanks,
Alan

Answer 1

Well I did some more experiments and I am able to at least create a connection pool within my example code:
package web;
import oracle.jdbc.pool.OracleDataSource;
import oracle.jdbc.OracleConnection;
import javax.naming.*;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;
public class ConnectionPool {
String message = "Not Connected";
public void init() {
OracleConnection conn = null;
ResultSet rst = null;
Statement stmt = null;
try {
Context initContext = new InitialContext();
Context envContext = (Context) initContext.lookup("java:/comp/env");
OracleDataSource ds = (OracleDataSource) envContext.lookup("App1ConnectionPool");
message = "Here.";
     String user = ds.getUser();
if (envContext == null)
throw new Exception("Error: No Context");
if (ds == null)
throw new Exception("Error: No DataSource");
if (ds != null) {
message = "Trying to connect...";
boolean cache_enabled = ds.getConnectionCachingEnabled();
if (!cache_enabled){
ds.setConnectionCachingEnabled(true);
Properties cacheProps = new Properties();
cacheProps.put("InitialLimit","5");
     cacheProps.put("MinLimit","5");
cacheProps.put("MaxLimit","10");
ds.setConnectionCacheProperties(cacheProps);
          conn = (OracleConnection) ds.getConnection();
Properties prop = new Properties();
prop.put("PROXY_USER_NAME", "adavey/xyz");
if (conn != null) {
message = "Got Connection " + conn.toString() + ", ";
          conn.openProxySession(OracleConnection.PROXYTYPE_USER_NAME,prop);
stmt = conn.createStatement();
//rst = stmt.executeQuery("SELECT 'Success obtaining connection' FROM DUAL");
rst = stmt.executeQuery("SELECT user, SYS_CONTEXT ('USERENV', 'SESSION_USER') from dual");
while (rst.next()) {
message = "DS User: " + user + "; DB User: " + rst.getString(1) + "; sys_context: " + rst.getString(2);
message += "; Was cache enabled?: " + cache_enabled;
rst.close();
rst = null;
stmt.close();
stmt = null;
conn.close(OracleConnection.PROXY_SESSION); // Return to connection pool
conn = null; // Make sure we don't close it twice
} catch (Exception e) {
e.printStackTrace();
} finally {
// Always make sure result sets and statements are closed,
// and the connection is returned to the pool
if (rst != null) {
try {
rst.close();
} catch (SQLException e) {
rst = null;
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
stmt = null;
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
conn = null;
public String getMessage() {
return message;
In my context.xml file, I tried to specify the same Connection Cache Properties as attributes, but no luck:
<Context path="/App1" docBase="App1"
debug="5" reloadable="true" crossContext="true">
<Resource name="App1ConnectionPool" auth="Container"
type="oracle.jdbc.pool.OracleDataSource"
driverClassName="oracle.jdbc.OracleDriver"
factory="oracle.jdbc.pool.OracleDataSourceFactory"
url="jdbc:oracle:thin:@127.0.0.1:1521:oddjob"
user="app1" password="app1"
ConnectionCachingEnabled="1" MinLimit="5" MaxLimit="20"/>
</Context>
These attributes seemed to have no effect:
ConnectionCachingEnabled="1" ; also tried "true"
MinLimit="5"
MaxLimit="20"
So basically if I could find some way to get these attributes set within the context.xml file instead of my code, I would be a happy developer :-)
Oh well, it's almost Miller time here on the east coast. Maybe a few beers will help me find the solution I'm looking for.