ArrayList over http??

Jim Kernsey

Hi

I'm trying to send an arraylist over http, but i've confused myself :rolleyes:

First up is this possible?

I have a pda running a thick client java program, it is using http to do a lookup on an EJB on my local machine. That is working fine.

I'm trying to invoke a method that will return an arraylist.

currently i can pass strings through a printwriter from the pda to a jsp. I now wish to to pass an arraylist.

can anyone give me some pointers to some example or does anyone have any ideas?

Cheers

Evil Phil

Could you convert the arraylist into XML and pass that?

Jim Kernsey

good question.

how do i do that??

do you know of any examples anywhere?

damnyanks

Check XMLEncoder int he JAVA API.

Enygma

Well what are the objects in the ArrayList?
Are they just Strings?

You could just send something like this over HTTP:

<arrayList>
   <element index="0">String Value Here</element>
   <element index="1">String Value Here</element>
   <element index="2">String Value Here</element>
   <element index="3">String Value Here</element>
</arrayList>

It sounds like there's a more fundamental problem though with your design. Does your PDA client call a JSP page that calls the EJB? And then you want you PDA to be able to access the ArrayList? Can't you just skip the JSP part and do the EJB lookup directly from the PDA?

OfflerCrocGod

What's wrong with ObjectOutputStream?

Jim Kernsey

Enygma wrote:

Can't you just skip the JSP part and do the EJB lookup directly from the PDA?

Ideally this is what i'd like to do, My EJB are in JBoss and the PDA is using IBM's j9 VM, There is a scaled down rmi package in it, but i think is so scaled down that I can't use an initial context in my look up?? I'm a little out of my depth!


I currently have a login that calls a jsp that does the login, the username and password are passed in the URL.

I can leave the arrayList as an array of strings if necessary.

Thanks for the advice so far

Jim Kernsey

OfflerCrocGod wrote:

What's wrong with ObjectOutputStream?

This is what i'm currently trying, banging my head off a brick wall!!

comanche

Jim Kernsey wrote:

This is what i'm currently trying, banging my head off a brick wall!!

should be able to serizlize it alright. if it is not a complex object, why not use the http headers!?

OfflerCrocGod

Jim Kernsey wrote:

This is what i'm currently trying, banging my head off a brick wall!!

Show some code, what part are you having difficulty with? It should be very easy stuff it's only a couple of lines of code. It shouldn't be a Serializable problem because it implements it so it may just be something to do with the socket output stream handling, it can only be used in one type or reader by the way you can't keep on re-using it so make sure you use ObjectOutput(Input)Streams at both end and only those, nothing else.

madramor

Jim Kernsey wrote:

currently i can pass strings through a printwriter from the pda to a jsp. I now wish to to pass an arraylist.

when you say strings you mean text, because strings are java objects just
like arraylists are java objects.

in order to keep your application open and expandable you should only communicate using text using a printwriter.

other wise if you use a client running on a pda using c++ it will not be able to
read the java object arraylist but it will be able to read the xml format stated
previously

Enygma wrote:

Can't you just skip the JSP part and do the EJB lookup directly from the PDA?

same issue here if you did a direct ejb lookup it would restrict you to using
java only.
where as http protocol can be implemented by any language


so you should process the arraylist on the server side and send it to the
client as xml/text (see Enygma post)

Jim Kernsey

Just to clarify waht i'm trying to do.

I have a PDA thar is running a java VM, I'm developing a thick client on the PDA in java (J2ME CDC - J9) . I have an existing set of EJB's running on my JBOSS server, I want to resue these EJB's by writing a JSP page that can invoke a method that returns an arraylist. I have a login working where I use a printwriter to login, passing username and password, the jsp invokes the login methods and returns the userID.

I'm now trying to return an arraylist, but i'm not really sure what to do, I think i should be using some ObjectOutput(Input)Streams but can't seem to find a good example of this.

I haven't really used ObjectOutput(Input)Streams or the like before so its a bit of a learning curve. Its prob something simple that I'm missing out on.

I'm not sure how to serialize the array into the appropriate stream and deserialize again.

Any help would be appreciated, thanks for the advice so far.

Evil Phil

You should post the code you think is causing the problem, then people will have a much better idea of what you're trying to achieve.

Ardent

I'm with Phil, I'd have gone down the XML route, easiest solution.

Anyhow, have a look at this - it may well address the issues you are experiencing:

http://www.microjava.com/articles/J2ME_J2EE_Integration_Strategies.pdf

Jim Kernsey

Hi

Appologies for taking so long to post the code, but the machine I was working on didn't have internet access!

I apologise for the mess, but I was spiking on this technology and I haven't had time to clean it up much.

Also I now have it working (partially) I am receiveing the array, but the server is throwing getOutputStream has already been called??


The JSP page

<html>
<head>
<%@ page
import = "javax.servlet.http.HttpServletRequest"
import = "javax.servlet.http.HttpServletResponse"
import = "javax.rmi.PortableRemoteObject"
import = "java.rmi.*"
import = "java.util.Hashtable"
import = "javax.ejb.CreateException"
import = "javax.naming.InitialContext"
import = "java.io.*"
import = "java.util.ArrayList"
%>
<title>Create User Profile</title>
</head>
<body bgcolor="#FFFFFF">

<%
System.out.println ("1");
String remoteAddress = request.getRemoteAddr().toString();
System.out.println ("");
String localAddress = request.getRemoteAddr().toString();
System.out.println ("3");
String contextPath = request.getContextPath().toString();
System.out.println ("4");
String protocal = request.getProtocol().toString();
System.out.println ("5");
String remoteHost = request.getRemoteHost().toString();
System.out.println ("6");

String scheme = request.getScheme().toString();
System.out.println ("7");
String serverName = request.getServerName().toString();
System.out.println ("8");
String sessionString = request.getSession().toString();
System.out.println ("9");


System.out.println ("remoteAddress: " + remoteAddress);
System.out.println ("localAddress: " + localAddress);

System.out.println ("contextPath: : " + contextPath);
System.out.println ("protocal" + protocal);


System.out.println ("remoteHost: " + remoteHost);

System.out.println ("scheme: " + scheme);
System.out.println ("serverName: " + serverName);
System.out.println ("sessionString: " + sessionString);

Hashtable props = new Hashtable();
String message = "";



props.put(
InitialContext.INITIAL_CONTEXT_FACTORY,
"org.jnp.interfaces.NamingContextFactory");
props.put(InitialContext.PROVIDER_URL, "jnp://127.0.0.1:1099");

InitialContext initialContext = new InitialContext(props);

Object obj = initialContext.lookup(ie.dit.bb.session.BestBetAccessHome.JNDI_NAME);

ie.dit.bb.session.BestBetAccessHome bestBetAccessHome = (ie.dit.bb.session.BestBetAccessHome) PortableRemoteObject.narrow(obj,ie.dit.bb.session.BestBetAccessHome.class);

try {

ie.dit.bb.session.BestBetAccess myMeetingManagerSessionBean = (ie.dit.bb.session.BestBetAccess) bestBetAccessHome.create();

ArrayList temp = myMeetingManagerSessionBean.getRaces();

ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream os = new ObjectOutputStream(baos);

System.out.println("sss" + temp.size());
os.writeObject(temp);

byte[] data = baos.toByteArray();

response.setContentType()

OutputStream output = response.getOutputStream();
output.write(data);
output.close();

} catch (RemoteException e) {
e.printStackTrace();
} catch (CreateException e) {
e.printStackTrace();
} catch (ClassCastException e) {
e.printStackTrace();
}

%>

</body>
</html>


here is my cllient :


package client;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.util.ArrayList;

import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;


public class Communications {
public Communications() {

}


public ArrayList validateLoginServlet(String userName, String password) throws IOException
{

loginDetails = loginServlet();
return loginDetails;
}

public ArrayList loginServlet() throws IOException {
ArrayList newList = new ArrayList();
System.out.println("1");
HttpConnection http = null;
String loginString = "";
InputStream iStrm = null;
String url = "http://localhost:8080/BestBet/validatelogin.jsp


try
{

System.out.println("3");
http = (HttpConnection) Connector.open(url);
System.out.println("4");
http.setRequestMethod(HttpConnection.GET);
System.out.println("5");
if (http.getResponseCode() == HttpConnection.HTTP_OK )
{

System.out.println("6");
ObjectInputStream ois = new ObjectInputStream(http.openInputStream());
System.out.println("7");
newList = (ArrayList) ois.readObject();
System.out.println("8");
ois.close();

System.out.println(newList.get(1).toString());

System.out.println("9");

}
}

catch (Exception e)
{
System.out.println (e);
}
finally
{

}
return newList;
}



}





Sorry about the mess of the code:

I have a nagging feeling that my jsp should be a servlet - haven't written one before but i suppose there is a first time for everything.

Thanks for your help so far.

Any ideas whats causing the error??

Jim Kernsey

Hey I got that working

couldn't see the wood for the trees!

here's the code i used in the end

http = (HttpConnection) Connector.open(url);
http.setRequestMethod(HttpConnection.GET);
if (http.getResponseCode() == HttpConnection.HTTP_OK ) {
ObjectInputStream ois = new ObjectInputStream(http.openInputStream());
races = (ArrayList) ois.readObject();
ois.close();