How do I pool Oracle connections in Tomcat? - oracle

Question

I'm unclear on the appropriate way to set up connections to an Oracle RAC database in Tomcat via context.xml. THIS method works for me:
<Resource
name="jdbc/mydb"
auth="Container"
type="javax.sql.DataSource"
driverClassName="oracle.jdbc.OracleDriver"
url="jdbc:oracle:thin:<connection details>"
username="<username>"
password="<account>"
maxTotal="150"
maxIdle="10"
/>
But is that using a connection pool? I tried adding factory="org.apache.tomcat.jdbc.pool.DataSourceFactory", as suggested at https://tomcat.apache.org/tomcat-8.0-doc/jdbc-pool.html, and mysteriously with that one change, I started getting:
java.sql.SQLException: ORA-01017: invalid username/password; logon denied
If I instead try type="oracle.jdbc.pool.OracleDataSource" and factory="oracle.jdbc.pool.OracleDataSourceFactory" I get:
Error: Unable to obtain a JDBC connection from Datasource:
java.lang.Exception: Error: Unable to obtain a JDBC connection from Datasource:
I've looked all over, but it's not clear to me what the best practice is for this. Ideas?

Answer 1

I am adding this answer to clarify my earlier comments, and for future visitors to this question.
Summary
Both of the following approaches will use DB connection pools:
Use Tomcat's newer, default DBCP 2 pool with type="javax.sql.DataSource".
Use Tomcat's older JDBC pool with factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" and type="org.apache.tomcat.jdbc.pool.DataSource".
I don't know enough about the differences to give any strong recommendations re. using one over the other.
The Default DBCP 2 Tomcat Pool
To make use of the default Tomcat DB connection pool, via a JNDI resource, you should follow the instructions provided on this Tomcat documentation page: JNDI Datasource How-To
Specifically, you need to use type="javax.sql.DataSource".
Here is a very basic resource configuration - not suitable for production, but useful to illustrate the approach. And it's for MySQL not Oracle, so there will be some adjustments needed:
<Resource name="jdbc/my_db"
auth="Container"
type="javax.sql.DataSource"
initialSize="5"
username="db_user"
password="***"
driverClassName="com.mysql.cj.jdbc.Driver"
url="jdbc:mysql://localhost:3306/mytestdb" />
When using initialSize="5", I saw the 5 expected connections on the DB server.
In the JVM, a connection pool was created - as shown in this VisualVM heap dump:
Here we can see that the pool is created, it has 5 connection objects, and it is using Tomcat DBCP - which, in turn, is a fork of Apache Commons DBCP 2.
DBCP 2 provides support for JDBC 4.1.
Tomcat's Home-Grown JDBC Pool
If you look at the Tomcat documentation on this other page - The Tomcat JDBC Connection Pool - you will see different guidance.
Specifically it states that you need both of the following in your <Resource>:
factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
type="org.apache.tomcat.jdbc.pool.DataSource"
If you use this, you will also be using a DB connection pool - but it will be based on the older Tomcat JDBC pool package:
In this example, I used initialSize="3".
In the Tomcat documentation this is presented as "a new connection pool" (it was a replacement for the previously used Commons DBCP 1.x). It's not as new as the Tomcat default DBCP 2 solution. I think the documentation wording is out-of-date, now. And somewhat confusing, because of that.
Additional Notes
Notes from a member of the Tomcat commit team (see here):
Tomcat JDBC is Tomcat's "home grown" database connection pooling and does not use poolPreparedStatements
Tomcat DBCP is Tomcat's package renamed fork of Apache Commons DBCP 2.
Tomcat DBCP is used by default.
You can always choose to implement a pool directly in your code, without using a JNDI <Resource> annotation. There are many available options.
(In my initial tests, there was a problem with my Tomcat installation which resulted in the creation of too many connections for DBCP 2. That misled me, initially).

Answer 2

Oracle Universal Connection Pool (UCP) is a Java connection pool that you can use as well. It is feature rich and works well with Oracle RAC, DG etc., Check out UCPServlet for an example.