Database connections for servlet threads?

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;
    }
}

It completely depends on how a connection is obtained, but you haven't shown or described any relevant code. — Matt Ball, Nov 05 '12 at 14:57
@MattBall ; code added. As you can see I make the connection when the servlet is initialised. — tomaytotomato, Nov 05 '12 at 15:13

score 4 · Accepted Answer · answered Nov 05 '12 at 15:02

4

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.

answered Nov 05 '12 at 15:02

Tomasz Nurkiewicz

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Give my question a +1 please :0 – tomaytotomato Nov 05 '12 at 16:22

score 1 · Answer 2 · answered Nov 05 '12 at 15:00

Depending on how you write your Connection, it can be per-servlet (instance variable) or global (static variable - providing you are not in a cluster environment and you manage concurrency, which would be a severe bottleneck)

However, if you want to make your system efficient, reliable, scalable, more easily mantainable and not having to implement more advanced feature such as reconnect in case of a link failure (which I think is the case considering your backend is Oracle) you should look into your application server connection pooling mechanisms.

Thanks, this application will be running on a single box in a dusty room somewhere. :) — tomaytotomato, Nov 05 '12 at 15:14

Database connections for servlet threads?

2 Answers2