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I am trying to use postgresql driver with tomcat. but when i run tomcat I am getting FileNotFound exception(Class.forName("org.postgresql.Driver")). Is tomEE aware of maven dependency. how can I overcome it

Victor Fries985
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    Does this answer your question? [Where to put 3rd party libs when using Maven with Tomcat?](https://stackoverflow.com/questions/28638944/where-to-put-3rd-party-libs-when-using-maven-with-tomcat) – jhamon Jan 13 '20 at 16:49
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    No [TomEE](https://tomee.apache.org/) is not aware of maven dependencies, since Maven is a build tool, and TomEE is only interested in the jar, war, ear file *created* by the build, and doesn't care what tool was used to *do* the build. TomEE does however provide Maven plugin to *help* with the build. – Andreas Jan 13 '20 at 17:02

1 Answers1

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No. Maven not involved after Tomcat/TomEE deployment

No, TomEE does not know about Maven or your POM.

As commented by Andreas, your Maven-driven web-app project will produce a WAR file or EAR file. That file contains any dependencies you may have configured in your POM.

For deployment, you will be moving that WAR or EAR file to the TomEE server. At that point there is no more Maven involvement.

These comments above apply to your eventual deployment for production. While in development, you may be using an IDE such as IntelliJ/NetBeans/Eclipse that can call upon an external web container such as Tomcat or TomEE to run and debug your web app. Maven settings may be involved in that special case, as part of hooking up your IDE to the external web container. Even in this special case, Tomcat/TomEE is not aware of Maven having possibly participated in its launching or configuration.

JDBC drivers are special

Furthermore, deploying a JDBC driver to Tomcat, TomEE, or other Jakarta Servlet container is a complicated matter because of classloader issues and the JDBC driver registration process. Generally, you should not be bundling a JDBC driver within your WAR/EAR.

Search Stack Overflow to learn more. Remember that TomEE is built on Apache Tomcat, so most anything you read about Tomcat applies.

See:

By the way, in modern Java with its JDBC driver registration feature (DriverManager), you no longer need to call Class.forName. That call is now legacy.

DataSource

Tip: Learn to use a DataSource implementation provided by your driver. Regarding Postgres, if using the JDBC driver from jdbc.postgresql.org, see this chapter.

PGSimpleDataSource pgDataSource = new PGSimpleDataSource();
pgDataSource.setDataSourceName("Acme Corp invoicing database");
pgDataSource.setServerName("localhost");
pgDataSource.setDatabaseName("test");
pgDataSource.setUser("testuser");
pgDataSource.setPassword("testpassword");

DataSource dataSource = pgDataSource ;  // Perhaps save as an "attribute" on your web app's "context".

Ask the data source for a Connection object when needing to talk to the database. Usually best to use try-with-resources syntax.

try 
(
    Connection conn = dataSource.getConnection() ;
) 
{
    … do your database work
}

Later you can learn to configure this DataSource info externally, outside your code base. That configuration is done through JNDI and a naming server such as the LDAP-style server built into Tomcat.

Basil Bourque
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  • seems like pgpoolingdatasource is deprecated – Victor Fries985 Jan 14 '20 at 08:44
  • @VictorFries985 Yes. Here I show the non-pooling `DataSource` implementation `PGSimpleDataSource`. Connection pooling is surprisingly complicated and difficult to do properly and thoroughly. Personally, I recommend avoiding connection pooling unless you have a significant problem that can be proven to be resolved with pooling. If you must do connection pooling, there are some Postgres products for that, such as *PG Bouncer* and *PG Pool*. – Basil Bourque Jan 14 '20 at 16:35