Slide 1 EE557: Server-Side Development eXtensible Stylesheet Language (XSL) XSL is the language that describes how XML documents are displayed XSL developed by the W3C Working Group Consists of three parts - XSLT (XSL Transformations) - XSL Formatting Objects (XSL-FO) - XPath XSLT – is the language that specifies the conversion of a document from one format to another, where the XSL stylesheet defines the means -> typically used for for textual transformations, such as HTML or WML from XML XSL-FO – formatting objects used when converting XML into binary formats such as PDF files, or Word Documents. This part is not covered by JAXP or here XPath – allows you to specify the part of the structure you are talking about It allows you to distinguish between and -> We can describe different transformations for different elements

Slide 2 EE557: Server-Side Development David Molloy John Peter Smith Jane Grogan xslexample1.xml

Slide 3 EE557: Server-Side Development xslexample1.xsl stylesheet is the top level element -> root of the XSL stylesheet tree associates the template with the root of the doc works like a ‘for’ loop selects the value of the tag within the root element Employee Firstname: Lastname:

Slide 4 EE557: Server-Side Development Client-Side/Server-Side Transformations

Slide 5 EE557: Server-Side Development Client-Side/Server-Side Internet Explorer 5.0+ goes a long way towards implementing client side transformations of XML Non standards compliant in many ways with some omissions/changes Perform a client transformation example Many advantages in performing a manual transformation on the server - works across multiple browsers (HTML) - lightweight clients - transformations are performed in advance – quicker java –classpath.;xalan.jar org.apache.xalan.xslt.Process –IN xslexample1.xml –XSL xslexample1.xsl -OUT xslexample1.html Work through second example in the notes xslcustomers.xml/.xsl

Slide 6 EE557: Server-Side Development XSLT and JAXP Often need to perform transformation real-time with dynamic data Eg. XML to browser-specific HTML XML to Wireless Markup Language (WML) for mobile phones Personalized webpages/documentation JAXP contains four packages responsible for handling XSLT - javax.xml.transform - javax.xml.transform.dom - javax.xml.transform.sax - javax.xml.transform.stream

Slide 7 EE557: Server-Side Development XSLT and JAXP Steps: 1) Import javax.xml.transform package classes and other classes such as DOM packages if you use DOM 2) Instantiate a TransformerFactory object TransformerFactory tFactory = TransformerFactory.newInstance() 3) Create a Transformer, in which we can define a set of transformation instructions. In our example, we supply an XSL StreamSource 4) Perform the transformation on the input (which can be created from a SAX reader, a DOM or an input stream) – in our example, we provide a DOMSource. The transform method takes a second argument, which in our example is a File (via a FileWriter) 5) Handle the possible exceptions Work through the example in the notes

Slide 8 Messaging with Java Most common form of message is This is person-to-person or server-to-person messaging, not application to application messaging is made up of a Header and Content Each header attribute has its own line, with attributes split by a ‘:’ Eg. Precedence: bulk From: “David Molloy” Show full message from the notes EE557: Server-Side Development

Slide 9 Messaging with Java messages are stored or sent using one of a number of different protocols - Simple Mail Transfer Protocol (SMTP) - Post Office Protocol (POP3) - Internet Message Access Protocol (IMAP4) IMAP4 typically considered more advanced than POP3, since it supports folders and status flags (among other features) EE557: Server-Side Development

Slide 10 JavaMail API J2EE developer does not need to understand underlying protocols JavaMail API includes providers for the most commonly used protocols JavaMail sits on top of the electronic mail vendor’s systems Provides a standard, independent framework for Java client applications to use electronic mail Can use JavaMail to: - Compose messages (including multi-part messages with attachments) - Send messages to particular servers - Retrieve and store messages in folders When using JavaMail, the application needs network access to a mail service that can send messages to the destination (dialup or network service) EE557: Server-Side Development

Slide 11 JavaMail API JavaMail is contructed with an Open Architecture, so can support future protocols and standards Two different types of protocols providers can implement: - Transport: is the service which sends messages to the destination Most commonly used transport is SMTP - Store: the service that provides access to messages that have been delivered to a mailboc. Most commonly used is POP3 but IMAP4 is considered better and becoming more common JavaMail relies heavily on the Java Activation Framework (JAF). JAF designed to work in a standard way with different types of data When an application needs to work with a particular data type, these JAF objects can be “activated” and used to process data (mail.jar, activation.jar, J2EE standard inclusion) EE557: Server-Side Development

Slide 12 JavaMail API javax.mail.Session class is starting point for JavaMail. Allows the specification of properties, such as the transport mechanism and the mail server Using the Session we can create a new MimeMessageObject We then set the properties for the message, such as the sender, recipient, subject and contents of the message Finally, we use Transport.send(message) to open up a new connection to the mail service and send the message Show the example code -> issues with running application (local access only etc.) - demoMail.java EE557: Server-Side Development

Slide 13 Java Message Service (JMS) JavaMail is an API for Messaging using Java Message Service (JMS) is an API for Messaging between applications Developed by Sun Microsystems as part of the Java 2 Enterprise Ed. Provides a common way for Java programmers to create, send, receive and read an enterprise messaging system’s messages “A message is a unit of data that is sent from a process running on one computer to other processes running on the same computer or a different computer” Messages can be simple text, or more complicated structures such as Java Hashtables or other serializable Java objects Object is serializable if it can be transmitted across a network as a series of bytes and re-created into a copy of the original object EE557: Server-Side Development

Slide 14 MOM is a specialized type of middleware that coordinates the sending and receiving of messages Provides dependable mechanisms that enable applications to create, send, and receive messages asynchronously in an enterprise environ. Numerous examples of MOM: - IBM MQ Series - Fiorano Message Server - Progress SonicMQ - SilverStream JbrokerMQ -> JMS provides a standard interface to these MOM products Frees developers from having to write low level infrastructure code, also known as “plumbing”, allowing them to build solutions quicker JMS is used and integrates with other components of J2EE (eg. JDBC used for persisting messages, JMS used in MDBs) EE557: Server-Side Development Java Message Service (JMS)

Slide 15 Two primary communication modes: EE557: Server-Side Development Java Message Service (JMS) 1.Synchronous Communication: conducted between two parties, both parties must be active and must acknowledge receipt of a message (known as a blocking call) before proceeding - easily affected by hardware, software and network failures, resulting in delayed messages and traffic backups - if hardware capacities are exceeded information is typically lost - Example: chat application 2.Asynchronous Communication: all parties are peers and can send messages at will. Does not require real-time acknowledgement of messages. Requester can continue with other processing once it sends the message (known as a non-blocking call) - Example: . Even though your client may not be running on your PC, people can still send multiple messages to you. - Example: internet-based purchase ring tone system -> return feedback to browser, mobile phone turned off/no signal?

Slide 16 Using messaging for exchanging data provides for: EE557: Server-Side Development Java Message Service (JMS) - Easy integration of incompatible systems - Asynchronous communications - One-to-many communications - Guaranteed messaging - Transactional messaging (all or none, commit/abort) JMS supports two message models known as Point-to-Point (PTP) and Publish/Subscribe (Pub/Sub) Both models can deliver messages synchronously or asynchronously

Slide 17 Sends messages to a receiver on a one-to-one basis, such as in instant messaging, or sending an order to another system Message delivered to a queue -> processed on FIFO basis Only one receiver can process each message (regardless of number of receivers) Receiver can look through messages in a Queue (eg. To count them) but must process them FIFO EE557: Server-Side Development Point-to-Point Model (PTP)

Slide 18 Publish/Subscribe Model Applications can publish messages on a one-to-many or many-to-many basis. Eg. Sending news stories to interested parties, stock prices to traders Messages are published to a Topic -> one or more publishers can publish messages to a Topic -> clients must subscribe to receive messages -> typically must be subscribed in advance If no clients subscribed, messages are typically destroyed EE557: Server-Side Development

Slide 19 JMS API Programming Model Firstly, we set up a QueueConnectionFactory or a TopicConnectionFactory for use in our JMS applications We achieve this by using the Sun Application Server Admin Console (or whatever console is appropriate for the application server we are using). The steps to add the ConnectionFactory are detailed in the notes At beginning of JMS application, we perform a JNDI API lookup of the connection factory. Eg. Context ctx = new InitialContext(); QueueConnectionFactory queueConnectionFactory = (QueueConnectionFactory) ctx.lookup(“myQueueConnectionFactory”); EE557: Server-Side Development

Slide 20 We also need to define a ‘destination’, which will be either a Queue or a Topic. It defines the target of messages it produces and the source of messages it consumes Again we create this resource using the Admin Console In our Java application we perform a JNDI lookup for our destination: Queue myQueue = (Queue) ctx.lookup(“MyQueue”); Topic myTopic = (Topic) ctx.lookup(“MyTopic”); Obtain a QueueConnection/TopicConnection to the provider by using the QueueConnectionFactory or TopicConnectionFactory Obtain a QueueSession/TopicSession with the provider by using the QueueConnection/TopicConnection EE557: Server-Side Development JMS API Programming Model

Slide 21 JMS API Programming Model EE557: Server-Side Development Create a QueueSender or QueueReceiver (TopicPublisher or TopicSubscriber) via the QueueSession (TopicSession) for the required Queue (Topic) Send and/or receive messages (Publish and/or subscribe messages) Close the QueueConnection (automatically closes QueueSender/Receiver, and the QueueSession). For Pub/Sub, close the TopicConnection, TopicPublisher/Subscriber and TopicSession

Slide 22 JMS API Programming Model EE557: Server-Side Development

Slide 23 JMS Messages Typically formatted data (such as a request, event or status) passed between applications. Message can contain simple or complex data types, including Serializable Java objects JMS message is made up of 1 required component and 2 optional: - A header (required) – used for identifying and routing messages, setting expiration,priority etc. – many settable by clients - Properties (optional) – extra header information - A body (optional) – one of 5 different formats ByteMessage,ObjectMessage,TextMessage,StreamMessage and MapMessage (hashtable type) message = queueSession.createTextMessage(); for (int i = 0; i < NUM_MSGS; i++) { message.setText("This is message " + (i + 1)); System.out.println("Sending message: " + message.getText()); } EE557: Server-Side Development

Slide 24 Point-to-Point Example SimpleQueueSender.java SimpleQueueReceiver.java EE557: Server-Side Development Publish/Subscribe Example SimpleTopicPublisher.java SimpleTopicSubscriber.java TextListener.java