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copied!<p>Here is an answer I came to:</p> <p>First of all I have switched from <a href="http://jackson.codehaus.org/1.0.0/javadoc/org/codehaus/jackson/map/ObjectMapper.html" rel="nofollow noreferrer">ObjectMapper</a> to <a href="http://sites.google.com/site/gson/gson-user-guide" rel="nofollow noreferrer">Gson</a>. Define an abstract class and an enum of types:</p> <pre><code>public abstract class Message { private MessageType type; protected Message(){ type = setType(); } protected abstract MessageType setType(); public MessageType getType() { return type; } public void setType(MessageType type) { this.type = type; } } public enum MessageType { PRESENCE(PresenceMessage.class), TEXT(TextMessage.class); private Class<? extends Message> clazz; private MessageType(Class<? extends Message> clazz){ this.clazz = clazz; } public Class<? extends Message> getClazz() { return clazz; } } </code></pre> <p>Every class that extends the Message is the actual one we are sending over Json. It has to implement the getType() method.</p> <p>So when desirializing just use that code :</p> <pre><code> String line; BufferedReader reader = new BufferedReader(new InputStreamReader(get.getResponseBodyAsStream(),"UTF-8")); while ((line = reader.readLine()) != null){ builder.append(line); } if (clazz == Message.class){ String string = builder.toString(); Message message = gson.fromJson(string,Message.class); if (message.getType() == null) throw new IllegalStateException("Could not de-serialize message " + builder.toString() ); return (T)gson.fromJson(string,message.getType().getClazz()); } </code></pre> <p>I hope you can fill the missing parts by yourself.</p>

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