PoolingHttpClientConnectionManager 如何管理连接？

Question

I have a question and it is What is httpconnection of PoolingHttpClientConnectionManager?.

I know that If we use PoolingHttpClientConnectionManager , it reduces the time for spending connection establishment (such as ssl handshake , tcp enter code herehandshake etc) because it reuses the connections.

However, what I understand about http connection reusing is keep-alive and we can use it when server support it. If host doesn't support keep-alive connection, we cannot communicate with the host with keep-alive.

So, here are my questions,

If I use PoolingHttpClientConnectionManager to manage connections on non keep-alive server environment, does Connectionmanager manage connections? or it creates connection per request?

If ConnectionManager manages connections, how ConnectionManager keep connection? does the manager send bytes periodically?

Answer 1

If you don't define HttpClient will act as connection can be kept alive indefinitely, from Apache http docs :

If the Keep-Alive header is not present in the response, HttpClient assumes the connection can be kept alive indefinitely.

If you want to define Keep-Alive Strategy see example :

ConnectionKeepAliveStrategy myStrategy = new ConnectionKeepAliveStrategy() {
    @Override
    public long getKeepAliveDuration(HttpResponse response, HttpContext context) {
        HeaderElementIterator it = new BasicHeaderElementIterator
            (response.headerIterator(HTTP.CONN_KEEP_ALIVE));
        while (it.hasNext()) {
            HeaderElement he = it.nextElement();
            String param = he.getName();
            String value = he.getValue();
            if (value != null && param.equalsIgnoreCase
               ("timeout")) {
                return Long.parseLong(value) * 1000;
            }
        }
        return 5 * 1000;
    }
};