Question

With regards to servlets being multithreaded by default, does each servlet instantiate a database connection or is the connection shared between all threads of that servlet?

I am using JDBC as an interface between my servlet and an Oracle database.

If a database connection is shared between all threads, does this mean that I should use connection pooling to the database?

/** Open the connection here **/
public void init() {
    String url = "server";
    String username = "pwd";
    String password = "usr";
    try {
        Class.forName("oracle.jdbc.OracleDriver");
        conn = DriverManager.getConnection(url, username, password);
    } catch (Exception e) {
        System.err.println("Error making pool: " + e);
        conn = null;
    }
}

Answer 1

If a database connection is shared between all threads , does this mean I should use connection pooling to the database?

Yes, definitely! JDBC connections and single-threaded and not thread-safe. Just introduce connection pool in between, fetch connection first and close it as soon as you can during the same request.