Parameshwara,
On 8/1/25 12:15 AM, Parameshwara Bhat wrote:
I am working on a task of migrating a running a JSP/JSF application on
tomcat-6.0 to tomcat 9.0
My installation of tomcat-9.0.87 is on Opensuse-Leap-15.6. Database is
postgresql 17, using postgresql-42.7.7.jar for driver.
I am able to run legacy application on tomcat-9.0.87 after making
following changes ( picked up from tomcat-9.0 docs) to application's
connection code.
try {
InitialContext cxt = new InitialContext();
/*if ( cxt == null ) {
throw new Exception("Uh oh -- no context!");
}*/
DataSource ds = (DataSource) cxt.lookup(
"java:/comp/env/jdbc/public_PostgreSQL" );
/*if ( ds == null ) {
throws new Exception("Data source not found!");
}*/
try {
this.con = ds.getConnection();
} catch (SQLException ex) {
ex.printStackTrace();
}
} catch (NamingException e) {
e.printStackTrace();
}
/* this.con = DriverManager.getConnection(url,
username, password); */
You are never closing your connections, so you are leaking a connectin
from the pool every time this code runs.
I agree with Felix's assertion that using this.conn is likely a mistake.
While JDBC objects are theoretically thread-safe, they are not
practically so. For example, if one request (A) begins a transaction
while another request (B) is not expecting it, changes to the database
from request (B) might end up being rolled back if request (A) fails and
triggers a roll-back.
Besides, if you only need a single connection, what are you using a pool
for?
Or is this some kind of data-access object which is short-lived? Your
code gives no context.
I believe Tomcat's default behavior is to return the same DataSource
object each time you fetch it from JNDI, but I believe a sterict reading
of the specification suggests that the container is supposed to give you
a *new DataSource every time* which means that each time you get the
DataSource, you are requesting a completely new, distinct pool of
connections from the container.
I would recommend that you only obtain a DataSource from the container a
single time during application startup, and then use that (pooled)
DataSource repeatedly from your application.
My context.xml content is below.
<?xml version="1.0" encoding="UTF-8"?>
<Context path="/ERP">
<Resource auth="Container"
driverClassName="org.postgresql.Driver" maxTotal="40" maxIdle="20"
maxWaitMillis="-1" name="jdbc/public_PostgreSQL"
password="kapital" type="javax.sql.DataSource"
url="jdbc:postgresql://localhost:5444/das" username="das"/>
</Context>
Set maxTotal="1" for development and testing. Also, enable "abandoned
connection tracking". See the documentation for how to do that, and
you'll discover all your resource leaks fairly quickly.
-chris
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