XML Technology in E-Commerce

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XML Technology in E-Commerce
Lecture 4 Case Study XmlMessenger
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Lecture Outline

• Instant Messaging
• Case Study XMLMessenger
• Communication between client and server
• Application classes
• Sending and receiving XML through network
• User login
• Sending and receiving messages
• Summary

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OverviewXML Technologies and Applications
XML Docs Logical Structure Physical Structure
DTD XML Schema Meta-Modeling
XML Parser Well-formedness Validity
SAX
DOM
Applications E-Commerce
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Instant MessagingAn E-Commerce Application

• One of the most popular communication services
• 175 million users are expected by 2002
• Deployment on new client types is expected
  mobiles, PDAs, TVs
• Vendors
• AOL
• Yahoo
• Infoseek
• ICQ

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Case StudyXMLMessenger

• Simple Client/Server E-Commerce application
• Demonstrates some of XML capabilities utilized by
  the current eCommerce systems
• Platform and language independent data
  representation
• Standardized data exchange between involved
  parties
• Communication protocol implementation

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XML Messenger
Message to User 3
User 4
User 3
Message to User 1
Message to User 3
Messenger Server
Message to User 1
User 2
User 1
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XML MessengerLogin
ltusersgt ltusergtUser 2lt/usergt ltusergtUser
3lt/usergt lt/usersgt
User 3
ltupdate typelogingt ltusergtUser
1lt/usergt lt/updategt
ltusergtUser 1lt/usergt
ltnameInUse/gt
ltusersgt ltusergtUser 2lt/usergt ltusergtUser
3lt/usergt lt/usersgt
User 1
User 2
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XML MessengerMessages
ltmessage toUser 2 fromUser
1gt Hello! lt/messagegt
User 3
ltmessage toUser 2 fromUser
1gt Hello! lt/messagegt
Messenger Server
User 1
User 2
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XML MessengerLogout
ltupdate typelogoutgt ltusergtUser
1lt/usergt lt/updategt
User 3
ltupdate typelogoutgt ltusergtUser
1lt/usergt lt/updategt
ltdisconnect/gt
Messenger Server
User 1
User 2
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XML MessengerClass Diagram
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Class Responsibilities

• MessengerServer
• Listens for new client connections
• Maintains an in-memory XML document with online
  users
• Manages a set of threads (one thread per client)
• UserThread
• Communicates with a particular client
• MessengerClient
• Communicates with the corresponding thread on the
  server
• Manages client-side GUI

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Class Responsibilities

• ClientStatus
• Displays a list of online users
• Manages conversations with other users
• Conversation
• Displays the messages exchanged with a particular
  user
• Provides interface for entering a new message

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XML MessengerDemo

• Demo - Deitel 10, page 263
• Tools
• Java 1.2.2
• Java API for XML Processing (JAXP) 1.0.1
• Classes jaxp.jar and parser.jar
• Demo files
• MessengerServer.java
• UserThread.java
• MessengerClient.java
• ClientStatus.java
• Conversation.java

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ImplementationSending XML through network

• OutputStream output
• Document message
• try
• ((XmlDocument)message).write(output)
• catch (IOException e)
• e.printStackTrace()
• This fragment is used in
• MessengerClient, method send
• UserThread, method send

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ImplementationReceiving XML from network
InputStream input int bufferSize
0 bufferSize input.available() if
(bufferSize gt 0) byte buf new
bytebufferSize input.read(buf)
InputSource source new InputSource(
new ByteArrayInputStream(buf)) Document
message builder.parse(source) if (message !
null) messageReceived(messa
ge) This fragment is used in UserThread.run and
MessengerClient.runMessengerClient.
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ImplementationUser Login
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ImplementationUser Login
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User Login

• Login message creation (MessengerClient.java)
• factoryDocumentBuilderFactory.newInstance()
• builderfactory.newDocumentBuilder()
• public void loginUser()
• Document submitName builder.newDocument()
  
• Element root submitName.createElement("use
  r")
• submitName.appendChild(root)
• root.appendChild(
  submitName.createTextNode(name.getText()))
• send(submitName)

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User Login

• Getting output and input streams
  (MessengerClient.java)
• public void runMessengerClient()
• ...
• output clientSocket.getOutputStream()
• input clientSocket.getInputStream()
• Sending an XML message through the network
  (method send)
• try
• ((XmlDocument)message).write(output)
• catch (IOException e)
• e.printStackTrace()

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User Login

• Reading the XML message from the network stream
  (UserThread.java)
• public void run()
• ..
• int bufferSize 0
• bufferSize input.available()
• if ( bufferSize gt 0 )
• byte buf new bytebufferSize
• input.read(buf)
• InputSource source new InputSource(
• new ByteArrayInputStream(buf))
• Document message builder.parse(source)
  
• if ( message ! null )
• messageReceived(message)
• Class InputSource in package org.xml.sax

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User Login

• Analyzing the message (UserThread.java)
• public void messageReceived(Document
  message)
• Element root message.getDocumentElement()
  
• if (root.getTagName().equals("user"))
• String enteredName
  root.getFirstChild().getNodeValue()
• if (server.findUserIndex(enteredName)!
  -1)
• nameInUse()
• else
• send(server.getUsers())
• username enteredName
• server.addUser(this)
• .

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User Login

• Initialization of the document with user names
  (MessengerServer.java)
• private Document initUsers()
• Document init builder.newDocument()
• init.appendChild(init.createElement("users")
  )
• return init

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User Login

• Adding new user (MessengerServer.java)
• public void addUser(UserThread newUserThread)
  
• String userName newUserThread.getUsername(
  )
• updateGUI( "Received new user " userName
  )
• // notify all users of user's login
• updateUsers( userName, "login" )
• // add new user element to Document users
• Element usersRoot users.getDocumentElement
  ()
• Element newUser users.createElement(
  "user" )
• newUser.appendChild(
• users.createTextNode( userName ) )
• usersRoot.appendChild( newUser )
• updateGUI( "Added user " userName )
• // add to Vector onlineUsers
• onlineUsers.addElement( newUserThread )

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User Login

• Notification for new user login
  (MessengerServer.java)
• public void updateUsers(String userName,
• String type)
• Document doc builder.newDocument()
• Element root doc.createElement( "update" )
• Element userElt doc.createElement( "user" )
• doc.appendChild( root )
• root.setAttribute( "type", type )
• root.appendChild( userElt )
• userElt.appendChild(doc.createTextNode(userName
  ))
• // send to all users
• for (int i 0 i lt onlineUsers.size() i)
• UserThread receiver
  (UserThread)onlineUsers.elementAt( i )
• receiver.send( doc )

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Message Sending
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Message Sending
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Message Sending

• Construction of a message in the conversation
  window (Conversation.java)
• public void submitMessage()
• Document sendMessage
• sendMessage builder.newDocument()
• Element root sendMessage.createElement("mess
  age")
• root.setAttribute( "to", target )
• root.setAttribute( "from", clientStatus.getUse
  r() )
• root.appendChild(
• sendMessage.createTextNode(
  messageToSend ))
• sendMessage.appendChild( root )
• client.send( sendMessage )

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Message Sending

• Message handling in MessengerServer
• public void sendMessage(Document message)
• Element root message.getDocumentElement()
  
• String from root.getAttribute("from")
• String to root.getAttribute("to")
• int index findUserIndex(to)
• UserThread receiver
• (UserThread) onlineUsers.elementAt(index)
  
• receiver.send(message)

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Message Sending

• Message handling on the recipient side
  (MessengerClient.java)
• public void messageReceived(Document message)
• Element root message.getDocumentElement()
• if(root.getTagName().equals("message"))
• String from root.getAttribute( "from" )
• String messageText
  root.getFirstChild().getNodeValue()
• int index findConversationIndex( from )
• Conversation receiver
• (Conversation) conversations.elementAt(i
  ndex)
• receiver.updateGUI(from" "messageText)

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Summary

• Demonstration of XML technology for a simple
  E-Commerce application
• Implementation of a communication protocol with
  XML messages
• Handling of in-memory XML documents through DOM
  calls
• Sending and receiving XML through network
  connection

• Read Deitel 10
• Assignment
• Modify the login message to include information
  about login time. Update the user interface
  accordingly
• DeitelEx 10.4
• For more detailed explanation and some hints see
  the course site.