Re: [jetty-users] Communication between a Servlet and a custom protocol

[Josh Spiegel <joshlakewg@xxxxxxxxx>]

From the Connection, I can search Jetty Server for the right servlet context to find state set by the servlet (see code below).  But this seems a bit fragile and would appreciate it if anybody knows a cleaner solution.

Thanks,

Josh

Set from servlet:

  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    ServletContext s = this.getServletContext();

    s.setAttribute("foo", "foo value");

    ...

  }

Set from Connection:

  @Override

  public Connection newConnection(Connector connector, EndPoint ep) {

    ServerConnector sc = (ServerConnector)connector;

    System.out.println(findAttribute(sc.getServer(), "foo"));

       ....

    }

  private Object findAttribute(Server server, String name) {

    Deque<Handler> handlers = new ArrayDeque<Handler>();

    addHandlers(handlers, server.getHandlers());

    

    while (!handlers.isEmpty()) {

      Handler h = handlers.pop();

      if (h instanceof HandlerContainer) {

        addHandlers(handlers, ((HandlerContainer)h).getChildHandlers());

      }

      if (!(h instanceof WebAppContext)) {

        continue;

      }

      WebAppContext ctx = (WebAppContext)h;

      Object o = ctx.getServletContext().getAttribute(name);

      if (o != null) {

        return o;

      }

    }

    return null;

  }

  private void addHandlers(Deque<Handler> deque, Handler[] handlers) {

    for (Handler h : handlers) {

      deque.add(h);

    }

  }

  

On Mon, Jan 20, 2020 at 7:52 AM Josh Spiegel <joshlakewg@xxxxxxxxx> wrote:

I have the ConnectionFactory and the Connection implementations.

I have the Servlet (deployed in a war file)

The ConnectionFactory/Connection are deployed using a Jetty module/xml with start.jar.

The servlet is deployed by dropping the war file in webapps.

I have some dynamic state (mainly database connection pools) that I would like to share between the ConnectionFactory and the Servlet.  

I can set the state object as a context attribute from the servlet.  However, then it isn't clear to me how I would retrieve it from either the ConnectionFactory or Connection. 

Thanks,

Josh 

On Mon, Jan 20, 2020 at 1:29 AM Simone Bordet <sbordet@xxxxxxxxxxx> wrote:

Hi,

On Mon, Jan 20, 2020 at 12:36 AM Josh Spiegel <joshlakewg@xxxxxxxxx> wrote:
>
> Hi,
>
> What is the cleanest way for a servlet (e.g. in a war file under webapps) to communicate state with a custom ConnectionFactory running in the same server?

A custom ConnectionFactory typically creates Connections that parse
bytes that have been read from the network.
If that's the case, then your servlet should open a socket and write
the custom protocol bytes so that they can be read and parsed by the
custom Connection - basically you have to write a client for your
custom protocol.

> Is there is some way to set Server attributes from the servlet or something like that?

You need to detail what you want to do here, and consider the
lifetimes of the objects you want to deal with.
You do not want that a second request to the servlet overwrites the
attribute set by the first request.

> A static variable would probably work for me but I am hoping for something that is more decoupled and scoped at the Server level.

I doubt a static will work - would not be overwritten for every request?

Can you detail the problem first, rather than the solution?

--
Simone Bordet
----
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