Can Jersey's ServletContainer init method be overridden?

Writing a Web Service in Java (Jersey/Maven). I'd like to construct a class that builds a number of databases before the application is deployed - as all of its resources depend on those databases. Although there is a textual representation of the Jersey's ServletContainer source code, it has already been compiled into bytecode and packed into a jar and, thus, cannot be edited. Is the solution as simple as declaring an instance of the ServletContainer class in my code and overriding the init method there?

You can just do all your initialization in the ResourceConfig.

package org.foo;

public class AppConfig extends ResourceConfig {
    public AppConfig() {
        // initialize here
        packages("the.packages.to.scan");
    }
}

And you can declare it in the web.xml

<web-app>
    <servlet>
        <servlet-name>MyApplication</servlet-name>
        <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
        <init-param>
            <param-name>javax.ws.rs.Application</param-name>
            <param-value>org.foo.AppConfig</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>MyApplication</servlet-name>
        <url-pattern>/api/*</url-pattern>
    </servlet-mapping>
</web-app>

For other deployment options see Servlet-based Deployment