SIP IM设计思路

1。启动客户端界面程序InstantMessagingGUI，通过配置文件初始化SIP协议栈，界面以及好友列表；
2。初始化IM消息监听器ListenerInstantMessaging和用户代理IMUserAgent，ListenerInstantMessaging负责界面事件的处理，IMUserAgent实现接口SipListener；
3。IMUserAgent初始化IMAckProcessing，IMRegisterProcessing，IMByeProcessing，IMSubscribeProcessing，IMNotifyProcessing，IMInfoProcessing，IMMessageProcessing，IMPublishProcessing以及PresenceManager
用户代理IMUserAgent调用SipFactory来创建HeaderFactory，AddressFactory，
MessageFactory，SipStack；
4。SipStack创建ListeningPoint和SipProvider；
5。当点击注册按钮时，调用ListenerInstantMessaging的signMenuMouseClicked(MouseEvent mouseEvent)方法，该方法调用IMRegisterProcessing和IMPublishProcessing来进行处理登陆，imRegisterProcessing.signIn(localSipURL.trim())负责处理登陆，imRegisterProcessing.signOut(localSipURL.trim())负责处理离线退出。主要实现方法如下:
Request request=messageFactory.createRequest(requestURI,"REGISTER",
callIdHeader,cseqHeader,fromHeader,toHeader,viaList,maxForwardsHeader);
ClientTransaction clientTransaction=sipProvider.getNewClientTransaction(request);
clientTransaction.sendRequest();
如果用户选择离线，则imPublishProcessing.sendPublish(localSipURL.trim(),"offline")来发布离线消息。
6。IMUserAgent的方法processRequest(RequestEvent requestEvent)处理所有要发送的请求，主要实现如下：
if (request.getMethod().equals(Request.ACK)) {
                imAckProcessing.processAck(requestCloned, serverTransaction);
            }
            else if (request.getMethod().equals(Request.BYE)) {
                imByeProcessing.processBye(requestCloned,serverTransaction);
            }
            else if (request.getMethod().equals("MESSAGE")) {
                imMessageProcessing.processMessage(requestCloned,
serverTransaction);
            }
            else if (request.getMethod().equals("INFO")) {
                imInfoProcessing.processInfo(requestCloned,serverTransaction);
            }
            else if (request.getMethod().equals("SUBSCRIBE")) {
imSubscribeProcessing.processSubscribe
    (requestCloned,serverTransaction);
            }
            else if (request.getMethod().equals("NOTIFY")) {
                imNotifyProcessing.processNotify(requestCloned,serverTransaction);
            }
方法processResponse(ResponseEvent responseEvent)处理所有收到的响应，主要实现如下：
if ( response.getStatusCode()==Response.OK ||
                   response.getStatusCode()==202 ){
                     if (cseqHeader.getMethod().equals("REGISTER") ) {
                         imRegisterProcessing.processOK(responseCloned,clientTransaction);
                     }
                     if (cseqHeader.getMethod().equals("MESSAGE") ) {
                         imMessageProcessing.processOK(responseCloned,clientTransaction);
                     }
                     if (cseqHeader.getMethod().equals("BYE") ) {
                         imByeProcessing.processOK(responseCloned,clientTransaction);
                     }
                     if (cseqHeader.getMethod().equals("SUBSCRIBE") ) {
                         imSubscribeProcessing.processOK(responseCloned,clientTransaction);
                     }
     //Henrik Leion added NOTIFY processing
     if (cseqHeader.getMethod().equals("NOTIFY") ) {
                         imNotifyProcessing.processOk(responseCloned,clientTransaction);
     }
7。当用户注册登陆成功后，调用方法imRegisterProcessing.processOK(responseCloned,clientTransaction)来更新。更新界面显示，更新状态并且通知好友，订阅所有好友的状态，通知订阅的好友，重新打开正在进行的所有Chat sessions。好友的状态由PresenceManager来进行管理。
8。当用户状态改变时，通过如下方法：
IMNotifyProcessing imNotifyProcessing=imUA.getIMNotifyProcessing();
            imNotifyProcessing.sendNotifyToAllSubscribers("open",localStatus);
来通知订阅者
9。当要进行聊天时，实例化RemoteSipURLFrame，在RemoteSipURLFrame里输入要聊天的对方URL，点确定后，产生ChatSessionManager来对会话进行管理。ChatSession负责会话，ChatFrame是会话框，按发送按钮时，会调用ChatSession的方法chatSession.sendIMActionPerformed(ActionEvent evt);来发送消息，然后sendIMActionPerformed(ActionEvent evt)方法会调用IMMessageProcessing的imMessageProcessing.sendMessage(localSipURL,remoteSipURL,text,this);来发送消息。发送的时候，IMUserAgent的processRequest会调用IMMessageProcessing的processMessage(Request request,ServerTransaction serverTransaction)对远端发送的请求进行处理，processResponse方法会调用IMMessageProcessing的processOK(Response responseCloned,ClientTransaction clientTransaction)来对远端的响应进行处理。远端的消息请求处理完毕后，会更新本地ChatFrame的内容并且发送ok回响给对方。客户收到ok回响后，表示对方已经收到，那么就把本地type的消息内容删除，更新ChatFrame的内容