Clearing up DB resources on sessionDestroyed

Question

Hello, we have a session listener class tied to HttpSessionListener. What I want to know is what is the best way to release all DB resources and pending transactions in the sessionDestroyed event? For instance, if the user is running an update transaction and the app crashes somehow, I want to release all these transactions when the session invalidates. Is there something on the Connection object I can use?
Also, we are calling Oracle packages to do all of our transactions, not sure if that makes a difference in your answer.

Answer 1

Usually, database connections should be kept around for the smallest possible amount of time. They are a pretty expensive and scarce resource. Keep them in local variables, and use try/finally to release statements, result sets, and connections. Like so:
    void whatever()
        Connection connection = null;
        PreparedStatement stmt = null;
        ResultSet res = null;
        try {
            String sql = "select ...";
            connection = pool.getConnection(); // or however your connection pool works
            stmt = connection.prepareStatement(sql);
            res = stmt.executeQuery();
            while (res.next()) {
    } finally {
        // Close in reverse order of creation
        SqlUtil.close(res);
        SqlUtil.close(stmt);
        SqlUtil.close(connection);
public class SqlUtil
    public static void close(Statement stmt)
        if (stmt == null) // can be null if an exception occurred
            return;
        try {
            stmt.close();
        } catch (Exception e) {
            log.error(e, "error closing database statement");
    // ditto for ResultSet and Connection
    /* You could also write a close(ResultSet, Statement, Connection).
     * That has the advantage that it can close all three, and then throw an SqlException
     * if any of the closes failed.  Three separate closes can log the exception
     * but can't easily pass it upwards.
}