private String makeKey(String uri, String user, char[] password) {
        requireNonNull(uri);
        // user nullable
        // password nullable
        return uri + user +
            ((password == null) ? "null" : new String(password));
    }
Configuration parameter that controls if a request for a new connection
should be queued until one becomes available or if it should cause an
exception to be thrown if no connection is available.
runtime-parent/runtime-core/src/main/java/com/speedment/runtime/core/component/connectionpool/SingletonConnectionPoolComponent.java