Proxies

FlexyPool monitors connection pool usage and so it needs to intercept the connection close method call.
For simplicity sake, the first version was relying on dynamic proxies for this purpose:

private static class ConnectionInvocationHandler 
    implements InvocationHandler {

    public static final String CLOSE_METHOD_NAME = "close";

    private final Connection target;
    private final ConnectionCallback callback;

    public ConnectionInvocationHandler(
        Connection target, 
        ConnectionCallback callback) {
        this.target = target;
        this.callback = callback;
    }

    @Override
    public Object invoke(
        Object proxy, 
        Method method, 
        Object[] args) throws Throwable {
        if (CLOSE_METHOD_NAME.equals(method.getName())) {
            callback.close();
        }
        return method.invoke(target, args);
    }
}

As straightforward as it may be, a proxy invocation is slower than a decorator, which calls the target method using a direct invocation.
Because all connection pools use proxies anyway, adding another proxy layer only adds more call-time overhead and so now FlexyPool supports connection decorators as well.

Continue reading “How does FlexyPool support both Connection proxies and decorators” →