Question

I want to send send HashMap object to the applet that requested it. A servlet has that HashMap object. Is there a way I can do this ?

Applet ------requests HashMap object---->Servlet listens to this request
                                                 |
                                                 |
                                     Servlet searches that HashMap Object
                                                 |
                                                 |
                                                \ /
<--Finally Send this to applet------------ Servlet gets the HashMap object                                                                

I have made a connection to the servlet and my servlet also has the HashMap object,but I don’t know how to send it to the applet and I wonder if it can be sent !

Answer 1

I’m going to make use of some external libraries in order to answer your question: Google Gson and Apache IO Utils.

So you already have the HashMap in your Servlet and want to send it to the Applet:

Map<String, String> myMap = new HashMap<String, String>();// or whatever
Gson gson = new GsonBuilder().create();
String jsonString = gson.toJson(myMap);
IOUtils.write(jsonString, resp.getOutputStream());// where 'resp' is your HttpServletResponse
IOUtils.closeQuietly(resp.getOutputStream());

And to receive it in your Applet:

String jsonString = IOUtils.toString(conn.getInputStream()); // where 'conn' is an HttpURLConnection
IOUtils.closeQuietly(connection.getInputStream());
Gson gson = new GsonBuilder().create();
// The TypeToken is needed when Generics are involved
Type typeOfHashMap = new TypeToken<Map<String, String>>() {}.getType();
Map<String, String> myMap = gson.fromJson(jsonString, typeOfHashMap);

And that’s it. It’s just a simple example but I hope you get something out of it.

Of course you could be doing it by hand instead of using external libraries, but this way is much easier.