Source code
package TBA.Messages;
import TBA.Exceptions.MessagesException;
/**
* This class is the root of all messages between the client and
* the server. It handles the 'Message Header' section of the message only.
*<p>
* @author Dan McGrath
*
* @version $Rev:: 247 $ $Date:: 2009-10-23 #$
*/
public class Messages
{
private char messageType = '\0';
private String sessionID = null;
private int messageLen = 0;
private final int messageLenSize = 6;
private final int sessionIDLen = 36;
/** This field represents the length of the message header **/
public static final int messageHeaderLen = 43;//messageLenSize+sessionIDLen+1
/**
* Constructor does nothing
*/
public Messages(){ }
/**
* This method converts the message length (int) to the message length (hex)
* included the length of the message length field.
*<p>
* @param len The length of the message, not included the message length field
* @returns A zero-padded string of the message length
*/
private String FormatLen(int len)
{
len += messageLenSize;
return String.format("%0"+Integer.toString(messageLenSize)+"x", len);
}
/**
* The Get() Method adds the 'Message Header' to the beginning of the message
* passed into it. It automatically calculates the message length field
* for you.
*<p>
* @param childMessage The message to send, not including the 'Message Header'
*<p>
* @return The actual message string you can send
*<p>
* @throws MessagesException
*<p>
* @see #Set(java.lang.String)
*/
protected String Get(String childMessage) throws MessagesException
{
String message = null;
if(messageType == '\0')
{
throw new MessagesException("Message Type not set");
}
if(sessionID == null)
{
sessionID = String.format("%0"+Integer.toString(sessionIDLen)+"d",0);
} else if (sessionID.length() != sessionIDLen)
{
throw new MessagesException("Invalid Session ID");
}
if(childMessage == null)
{
childMessage = "";
}
message = Character.toString(messageType);
message += sessionID;
message += FormatLen(message.length()+childMessage.length());
message += childMessage;
return message;
}
/**
* The Set() Method takes a Message and strips out the message header information
* returning the rest of the message back so that it can then be processed.
*<p>
* @param message The message as recieved.
*<p>
* @return The message without the 'Message Header'
*<p>
* @throws MessagesException
*<p>
* @see #Get(java.lang.String)
*/
public String Set(String message) throws MessagesException
{
int messageLenPos = sessionIDLen + messageLenSize + 1;
String messageLenString;
if(message.length() < messageLenPos)
{
throw new MessagesException("The Message Header is incomplete");
}
messageLenString = message.substring(sessionIDLen + 2, messageLenPos);
try
{
messageLen = Integer.parseInt(messageLenString, 16);
}
catch(NumberFormatException ex)
{
throw new MessagesException("The Message length is formatted incorrectly!");
}
messageType = message.charAt(0);
if(messageType != 'R' && messageType !='Q')
{
messageType = '\0';
throw new MessagesException("The message is of an unknown type");
}
sessionID = message.substring(1, sessionIDLen+1);
return message.substring(messageLenPos, message.length());
}
/**
* This method returns the 'Message Type' field. You must have called either
* Set() or SetMessageType() first.
*<p>
* @return The Message Type. Possible values are:
* 'Q' for Query,
* 'R' for Response, or
* '\0' for Message not currently set.
*<p>
* @see #SetMessageType(char)
*/
public char GetMessageType()
{
return messageType;
}
/**
* This method allows you to set the Message Type in the 'Message Header'.
*<p>
* @param Type Valid values are 'Q' for query or 'R' for Response. All others
* will throw an exception
*<p>
* @throws MessagesException
*<p>
* @see #GetMessageType()
*/
protected void SetMessageType(char Type) throws MessagesException
{
if(Type != 'R' && Type !='Q')
{
messageType = '\0';
throw new MessagesException("The message type is invalid");
}
else
{
messageType = Type;
}
}
/**
* This method returns the message length
*<p>
* @return The Message length
*<p>
*/
public int GetMessageLen()
{
return messageLen;
}
/**
* This method gets the Session ID from the 'Message Header'. You must have
* called either Set() or SetSessionID() first.
*<p>
* @return The Session ID or null if one is not set.
*<p>
* @see #SetSessionID(java.lang.String)
*/
public String GetSessionID()
{
return sessionID;
}
/**
* This method allows you to set the 'Session ID' field.
*<p>
* @param ID The Session ID to set. Must be a 36-digit Hex number, as a string.
*<p>
* @throws MessagesException
*<p>
* @see #GetSessionID()
*/
public void SetSessionID(String ID) throws MessagesException
{
if(ID.length() != sessionIDLen)
{
sessionID = null;
throw new MessagesException("The SessionID invalid");
}
else
{
sessionID = ID;
}
}
}