How to transfer data from one jsp to another jsp with sockets

Question

I have 3 .jsp's. The first one asks the user for their username. Once the form is submitted it is taken to a 2nd jsp where a unique passcode is created for the user. How would I go about taking this passcode and passing it to a 3rd jsp using a socket?

Answer 1

You can use java.net.URL and java.net.URLConnection to fire and handle HTTP requests programmatically. They make use of sockets under the covers and this way you don't need to fiddle with low level details about the HTTP protocol. You can pass parameters as query string in the URL.

String url = "http://localhost:8080/context/3rd.jsp?passcode=" + URLEncoder.encode(passcode, "UTF-8");
InputStream input = new URL(url).openStream();
// ... (read it, it contains the response)

This way the passcode request parameter is available in the 3rd JSP by ${param.passcode} or request.getParameter("passcode") the usual way.

Better is however to just include that 3rd JSP in your 2nd JSP.

request.setAttribute("passcode", passcode);
request.getRequestDispatcher("3rd.jsp").include(request, response);

This way the passcode is available as request attribute in the 3rd JSP by ${passcode} or request.getAttribute("passcode") the usual way.

See also:

• Using java.net.URLConnection to fire and handle HTTP requests

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Unrelated to the concrete question, this is however a terribly nasty hack and the purpose of this is beyond me. There's somewhere a serious design flaw in your application. Most likely those JSPs are tight coupled with business logic which actually belongs in normal and reuseable Java classes like servlets and/or EJBs and/or JAX-WS/RS which you just import and call in your Java class the usual Java way. JSPs are meant to generate and send HTML, not to act as business services, let alone web services. See also How to avoid Java code in JSP files?

Answer 2

So, you want the username to be submitted from the first JSP to the second, by submitting a form to the second, right? But, for interaction between the second and third, you want to avoid using the communication mechanisms behind the the JSP files and use your own, right?

Well, how you might implement doing this depends on where you're sending your communication from and to. For instance, are they on the same machine, or on different machines?

Generally speaking, you'll need a client-server type of relationship to be set up here. I imagine that you would want your third JSP to act as the server.

What the third JSP will do is will sit and wait for a client to try to communicate with it. But, before you can do that, you'll first need to bind a port to your application. Ports are allocated by the Operating System and are given to requesting processes.

When trying to implement this in Java, you might want to try something like the following:

int port_number = 1080;
ServerSocket server = new ServerSocket(port_number);

In the above example, the ServerSocket is already bound to the specified port 1080. It doesn't have to be 1080 - 1080 is just an example.

Next, you will want to listen and wait for a request to come in. You can implement this step in the following:

Socket request = null;

while((request = server.accept()) == null)
{}

This will cause the server socket to keep looping until it finally receives a request. When the request comes in, it will create a new Socket object to handle that request. So, you could come back to your loop later on and continue to wait and accept requests, while a child thread handles communication using your newly created request Socket.

But, for your project, I would guess that you don't need to communicate with more than one client at a time, so it's okay if we just simply stop listening once we receive a request, I suppose.

So, now onto the client application. Here, it's a little bit different from what we had with the server. First off, instead of listening in on the port and waiting for are request, the client's socket will actively try to connect to a remote host on their port. So, if there is no server listening in on that port, then the connection will fail.

So, two things will need to be know, those are:

1. What's the IP Address of the server?
2. What port is the server listening in on?

There are short-cuts to getting the connection using the Java Socket class, but I assume that you're going to test this out on the same machine, right? If so, then you will need two separate ports for both your client and server. That's because the OS won't allow two separate processes to share the same port. Once a process binds to the port, no other process is allowed to access it until that port releases it back to the OS.

So, to make the two separate JSP's communicate on the same physical machine, you'll need both a local port for your client, and you'll need the server's port number that it's listening in on.

So, let's try the following for the client application:

int local_port = 1079;
int remote_port = 1080;

InetSocketAddress localhost = new InetSocketAddress(local_port);
Socket client = new Socket();  //The client socket is not yet bound to any ports.
client.bind(localhost);  //The client socket has just requested the specified port number from the OS and should be bound to it.
String remoteHostsName = "[put something here]";
InetSocketAddress remotehost = new InetSocketAddress(InetAddress.getByName(remoteHostsName),  remote_port);  //Performs a DSN lookup of the specified remote host and returns an IP address with the allocated port number

client.connect(remotehost);  //Connection to the remote server is being made.

That should help you along your way.

A final note should be made here. You can't actually run these two applications using the same JVM. You'll need two separate processes for client and server applications to run.