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MessageBoard
MessageBoard represents the in-memory repository of messages. It allows messages to be added and retrieved using a Hashtable. Because this entity need not be exposed, it doesn't implement any of the ActionForm interfaces.
Listing 5 MessageBoard.java
import java.util.Hashtable;
public class MessageBoard {
protected static MessageBoard singleton;
protected Hashtable messages = new Hashtable();
protected int count = 1;
protected MessageBoard() {
OOMessage firstMessage = new OOMessage();
String id = count + "";
firstMessage.setId(id);
messages.put(id, firstMessage);
count ++;
}
public synchronized OOMessage addMessage(Message msgElements,
String parentId) {
if (parentId == null || messages.get(parentId) == null) {
parentId = "1";
}
OOMessage parent = getMessage(parentId);
String id = count + "";
msgElements.setId(id);
OOMessage reply = new OOMessage(msgElements);
reply.setCurrentTimestamp();
reply.setParent(parent);
messages.put(id, reply);
count++;
return reply;
}
public OOMessage getRootMessage() {
return (OOMessage) messages.get("1");
}
public OOMessage getMessage(String msgId) {
return (OOMessage) messages.get(msgId);
}
public static MessageBoard getSingleton() {
if (singleton == null) {
singleton = new MessageBoard();
}
return singleton;
}
}
To provide scalability for the application, you would need to provide persistence for the messages—as in storing them in a database.
In the next article, you will develop the application’s view components.
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