Web Applications Engineering: Wrap-up

Transcription

1 Web Applications Engineering: Wrap-up Dr. Moshe Chai Barukh Service Oriented Computing Group, CSE, UNSW Week 12 M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 1 / 55

2 Acknowledgements Contents from this slides has been reused from Dr. H. Paik. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 2 / 55

3 Internet: IP (the address); TCP (communication, port numbers); DNS (Domain names); M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 3 / 55

4 Web: HTTP (hypertext transport); URL (Uniform Addressing); HTML (hypertext markup); Web Browsers and Web Servers M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 4 / 55

5 Web Applications: Dynamic interactions, changing states, getting things done!! M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 5 / 55

6 Developing a Web application Client-side programming - HTML/CSS, JavaScripts Server-side programming - Many solutions. Essentially it is a programming framework for processing HTTP dynamically. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 6 / 55

7 Separating Data from Presentation: XML <?xml version="1.0"?> <?xml-stylesheet type="text/xsl" href="staffcard.xsl"?> <staff> <name>helen Paik</name> <title>lecturer, UNSW</title> <extension>54095</extension> <photo src="me.gif" /> </staff> e.g., M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 7 / 55

8 Also worth mentioning that XML... is a well-supported standard data format (W3 standard) has free and standard parser support (SAX and DOM interfaces) has definition and validation support (e.g., Document Type Definition) has standard query languages (XPath, XQuery) has standard transformation language (XSLT) has many applications (SVG, MathML, CML, etc.) In many ways, Web applications and XML are inseparable. e.g, think of configuration files, development languages themselves, data exchange formats, and more. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 8 / 55

9 Servlets Java-based solution for server-side programming. Servlet Container manages the life-cycle of servlets (servlet config and context objects). Container does not exist load class Servlet Class Instantiate (constructor runs) init() Servlet Object constructor, init() service() Servlet (initialised) called once in the servlet's life destroy() service() destroy() handle client requests doget(), dopost(), etc. Each request runs in a separate thread. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week 12 9 / 55

10 Servlets: Web application contains... addressbook Web application: M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

11 Servlets: Parameter Data and Query Strings Query string? Parameters? Does order of parameters matter? How do you pass a String (including space and quotes) as arg s value? HttpServletRequest methods for accessing parameter data? M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

12 Servlets: Forms HTML forms elements are used to send parameters. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

13 Servlets: HTTP GET and POST POST (implications on the server-side?) GET (implications on the server-side?) M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

14 Servlets: Sessions HTTP is stateless... Issue Welcome Start Session Welcome Servlet Create a Journey object for the user Display Choices Menu Servlet Add Choice to Journey Show Journey so far Control Servlet Close Session Enough Servlet M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

15 Servlets: Sessions Use of Cookies (JSESSIONID), URL re-writing... User request response Travel-Application WelcomeServlet request response (sessid=50) request (sessid=50) response (sessid=50) request (sessid=50) response MenuServlet ControlServlet EnoughServlet (In the servlet container) SessionTable s25 user1 s29 user2 s36 user3 s50 user4 new entry for the new user SessionData id attribute address s25 s29 s36 s50 "JourneyFlag" "Queue" "Patron" "JourneyFlag" Memory jny2 obj jny obj SA WA Note: Cookies have more generic usage than just for sessions! M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

16 Servlets: Attributes Servlet Servlet read read write Context Attributes DB Connection ConcurrentUsers 42 Admin read read (HeadFirst, p.187) JSP Everyone in the application has access Session Attributes Servlet Servlet read write Shopping Cart A UserName Helen read JSP Accessible to only those with access to a specific HttpSession Servlet write Request Attributes OptionChoice Dark Beer read JSP Accessible to only those with access to a specific (Http)ServletRequest M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

17 JSP Presentation layer technology - should not be used for coding business logic. page directive include taglib JSP elements scripting action template (HTML bits...) declaration scriptlet expression standard custom Use less scripting more actions (e.g., using beans), EL (expression language), standard libraries like JSTL. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

18 DB layer (Data is important!) JDBC: java.sql.* SQL Query Java Program Driver Results DBMS JVM JDBC M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

19 DB layer: DAO Patterns DAO implementation: Cars CarNr Make Cost YPZ400 Ford 50 YPZ412 Ford 80 YPZ600 Mazda 80 WPZ600 BMW 100 WPZ610 BMW 200 WPZ620 BMW 250 PPZ410 Benz 250 PPZ420 Benz 350 PPZ430 Ford 150 YPZ420 Honda CarDTO carnr make cost CarDAOImpl. // plus Setter and Getter methods for these properties <<interface>> CarDAO List findall() { List findall() JDBC connect select * from cars create CarDTOs return CarDTO list } - Client Code - CarDAO.findAll() Loop display individual CarDTO M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

20 DB layer: ORM Mapping ORM (Object-Relational Mapping): Various paradigm mismatch problems (object world vs. relational/entity world) We want to call car.save(), rather than writing insert into statement Database JDBC Mappings Hibernate Configuration Client Code Java Objects What does Hibernate do for you? M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

21 MVC pattern It is the design pattern that glues your application together. Browser response request Container 1 Servlet (Controller) 4 2 JSP (View) 3 JavaBean (Model) 5 Data request Server Key: having a controller M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

22 A scenario: Building ShipFast.com Say you own a delivery service company and want to go online. Your business partners are online retail companies. Purpose of moving the operation online is (roughly) to allow your business partners to send the delivery requests online, calculate the quote and send it back to your partner notify the shipment to your partner when it is done KennyCD.com Customer KennyCD.com Site ShipFast.com Internet Business System Internet Business System M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

23 A Generic e-commerce Architecture A system typically consists of three layers and security layers. HTTP/ HTML Firewall Presentation Layer Firewall Proprietary Component Protocol Business Layer Database Access API Database Layer Each layer in the diagram has a purpose, architecture and an API. There are two leaders among the providers of this architecture and development frameworks: J2EE and Microsoft.NET M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

24 A Typical e-commerce Architecture Presentation Tier: responsible for working with clients (accepts HTTP request, returns HTML as response). Different browsers have different display capabilities. Presentation tier should deal with tailoring HTML to the specific client browser type (including mobile devices) Business Tier: responsible for business logic, typically this layer has packaged components working through well-defined interfaces (J2EE: EJB,.NET:COM+). It requires resources such as database connections, transaction management, etc. These resource requirements normally make it difficult to support a large number of clients. The presentation layer communicates with the business tier through a method transport protocol (eg., J2EE: RMI/IIOP,.NET: DCOM or SOAP) Database Tier: responsible for storing data. Communication between Database Tier and Business Tier use a specific API (J2EE: JDBC,.NET: ADO.NET) M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

25 ShipFast.com with.net Compare this to the generic architecture previously shown: presentation layer business layer HTTP/ HTML Firewall ASP.NET Firewall DCOM, MSMQ or SOAP COM+ using Visual Studio.NET.NET enterprise servers ADO.NET SQL Server or other ADO.NET compliant DB database layer M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

26 ShipFast.com with J2EE Compare this to the generic architecture and.net previously shown: HTTP/ HTML Firewall presentation layer JSP Firewall RMI / IIOP JMS or SOAP business layer EJB or JavaBeans JDBC J2EE services Any JDBC compliant DB database layer M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

27 Why Web Services? Companies rely on technologies to create efficiencies and expand market opportunities. More and more companies collaborate with a wider circle of suppliers, service providers and strategic partners. These companies must integrate their disparate applications. eg., Amazon.com Web services E-commerce services (third party suppliers): integrated through Amazon.com s ecommerce API which is based on Web Services Coding for Fun (an implementation example): com/coding4fun/archive/2006/10/31/ aspx M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

28 Going back to ShipFast.com KennyCD.com Customer KennyCD.com Site Business System (.NET) ShipFast.com KennyCD.com Customer TomBooks.com Customer Internet TomBooks.com Site Business System (PHP) Some Other Site Internet Business System (J2EE) Business System (J2EE) how can you communicate with KennyCD.com and many others? integration of heterogeneous business layers that talk different protocols and have different data type representation should be able to access remote functionality without being tied to specific languages or platforms M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

29 Existing technologies for accessing remote functionality Traditional Remote Procedure Calls (RPC):.NET Distributed COM (Component Object Model) J2EE Enterprise JavaBeans Java RMI and the list goes on... Need one idea to rule them all. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

30 Web Services Key concept: Allow applications to share data and invoke capabilities from other applications Without regard to how those applications were built, what operating system or platform they run on, and what devices are used to access them. Can be called across platforms and operating systems, regardless of programming language. Key facts: A standardised way of application-to-application communication based on XML open standards (ie., SOAP, WSDL and UDDI) over an Internet protocol backbone. Major developers include: Apache, IBM, HP, Sun and Microsoft M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

31 A bit about SOAP In late 1990, Microsoft started to think that their remote object access technology COM/DCOM is weak and that they need something that is cross-platform and naturally integrated with the Internet environment. With their.net initiative, they started developing a data transmit protocol called SOAP (Simple Object Access Protocol). The protocol is based on XML and uses HTTP, FTP and SMTP (Simple Mail Transfer Protocol) as a data transfer protocol. Microsoft perfected the SOAP standard, they open-sourced this by giving it to W3C. W3C made SOAP an official standard for XML messasging With other vendors following this standard, the way we access remote objects may finally become standardised... M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

32 SOAP and Web Services SOAP is a protocol for moving data across the Internet. Web services are the remote objects. They use SOAP to transmit data to and from client (client can also be a Web service) So, SOAP is a part of what makes Web Services possible, but that is not the complete picture of Web Services. Web service implementation platform providers: Microsoft.NET (locked with one Web server, IIS) Various Java implementations J2EE platforms (Jboss, Websphere, WebLogic) Apache Axis M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

33 Web Services Conceptual Architecture (IBM) Service Registry Service Description Find Publish Service Requestor Bind Service Provider Service Service Description M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

34 Web Services Conceptual Architecture (IBM) Three roles: service provider: develops an electronic service and registers its description at a publicly accessible service registry. service registry: hosts web services service requestor: query the registry to find an electronic service that meets his or her requirements. A binding occurs between the service provider and the service requestor. Main Web Services Standards: For service registry: UDDI, Universal Description, Discovery and Integration ( For service description: WSDL, Web-services Description Language ( For messages: SOAP, Simple Object Access Protocol ( M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

35 Interactions between WS and Client The web service provider declares his services within the UDDI register. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

36 Interactions between WS and Client The client looks for a Web service in the UDDI register Downloads the Web service s WSDL to build or generate a proxy (stub) for the web service M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

37 Interactions between WS and Client The client invokes the Web service through the user of the proxy via SOAP M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

38 XML Messaging Using SOAP M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

39 Simple Object Access Protocol (SOAP) A SOAP message is an XML document with predefined elements It also defines data encoding rules <?xml version= 1.0 encoding= UTF-8?> <SOAP-ENV:Envelope xmlns:soap-env=" xmlns:xsi=" xmlns:xsd=" <SOAP-ENV:Body> <ns1:dogooglesearch xmlns:ns1="urn:googlesearch" SOAP-ENV:encodingStyle=" <key xsi:type="xsd:string"> </key> <q xsi:type="xsd:string">shrdlu winograd maclisp teletype</q> <start xsi:type="xsd:int">0</start> <maxresults xsi:type="xsd:int">10</maxresults> </ns1:dogooglesearch> </SOAP-ENV:Body> </SOAP-ENV:Envelope> Specification: M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

40 Binding SOAP with a Transfer Protocol SOAP binding describes how a SOAP message is carried in a transport protocol (eg., HTTP, SMTP or FTP). For example, to bind SOAP to HTTP: A SOAP request is wrapped inside an HTTP POST The HTTP POST request specifies at least two HTTP headers: Content-Type and Content-Length. Content-Type: defines the MIME type for the SOAP message and the character encoding (optional) used Content-Length: specifies the number of bytes in the body of the SOAP request or response. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

41 An example of SOAP Binding over HTTP Here is a request to a web service for the current price of stock DIS: POST /StockQuote HTTP/1.1 Host: Content-Type: text/xml; charset="utf-8" Content-Length: nnnn SOAPAction: "Some-URI" <SOAP-ENV:Envelope xmlns:soap-env=" SOAP-ENV:encodingStyle=" <SOAP-ENV:Body> <m:getlasttradeprice xmlns:m="some-uri"> <symbol>dis</symbol> </m:getlasttradeprice> </SOAP-ENV:Body> </SOAP-ENV:Envelope> M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

42 An example of SOAP Binding over HTTP And here is the response from the service: HTTP/ OK Content-Type: text/xml; charset="utf-8" Content-Length: nnnn <SOAP-ENV:Envelope xmlns:soap-env=" SOAP-ENV:encodingStyle=" <SOAP-ENV:Body> <m:getlasttradepriceresponse xmlns:m="some-uri"> <Price>34.5</Price> </m:getlasttradepriceresponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope> M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

43 An example of SOAP Binding over SMTP To: From: Reply-To: Date: Tue, 15 Nov :27: Message-Id: MIME-Version: 1.0 Content-Type: text/xml; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE <?xml version=3d"1.0" encoding=3d"utf-8"?> <SOAP-ENV:Envelope SOAP-ENV:encodingStyle=3D" xmlns:soap-enc=3d" xmlns:soap-env=3d" xmlns:xsd=3d" xmlns:xsi=3d" <SOAP-ENV:Body> <m:echostring xmlns:m=3d" <inputstring>get your SOAP over SMTP here!</inputstring> </m:echostring> </SOAP-ENV:Body> </SOAP-ENV:Envelope> M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

44 Web Services Description Web Service Description is a machine-processable specification of the Web service s interface, written in Web Service Description Language (WSDL). Specification: The Web Services Description Language (WSDL) uses XML syntax. It describes a service in terms of the operations that make up the service, the messages that each operation requires, and the parts from which each message is composed. WSDL is used by the client to generate a proxy (stub) to the Web service. The proxy is then acts as a go-between between the WS and the client. This is usually done by a tool. M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

45 Web Services Description Definition Types Element Messages Part PortType Operation Input Output Binding Service soap:binding operation documentation port soap:address soap:operation Input Output M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

46 Google Web Service Google offers a web service that enables programmatic access to its search engine Three individual operations are provided: porttype of the Web service <porttype name="googlesearchport"> <operation name="dogetcachedpage"> <input message="typens:dogetcachedpage"/> <output message="typens:dogetcachedpageresponse"/> </operation> <operation name="dospellingsuggestion"> <input message="typens:dospellingsuggestion"/> <output message="typens:dospellingsuggestionresponse"/> </operation> <operation name="dogooglesearch"> <input message="typens:dogooglesearch"/> <output message="typens:dogooglesearchresponse"/> </operation> </porttype> How could we make use of these operations? M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

47 Google Web Service Suppose we want to produce an html file that provides an information link to each city whenever a city name is found in a document. The endelement() method in an SAX implementation. public void endelement(string uri, String localname, String qname) throws SAXException { try { if (localname.equals("person")) { Person = ec.tostring(); out.write("<tr><td>"+person+"</td>"); holcount = 0; } if (localname.equals("year")) { Year = ec.tostring(); if (holcount==0) out.write("<td>"+year+"</td>"); else out.write("<tr><td> </td><td>"+year+"</td>"); holcount++; } if (localname.equals("city")) { City = ec.tostring(); out.write("<td>"+city+"</td>"); String cityref = citygoogle.findcityref(city); out.write("<td><a href= "+cityref+" >" +cityref+"</a></td></tr>"); } } M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

48 Google Web Service This code performs a Google search for the city. import com.google.soap.search.*; public class citygoogle { public static String findcityref(string City) { try { GoogleSearch s = new GoogleSearch(); s.setkey("fqzjxy+rqqo7d0hynway+xqn5keahfpl"); s.setquerystring(city); GoogleSearchResult r = s.dosearch(); GoogleSearchResultElement[] elements = r.getresultelements(); if(r.getstartindex() > 0) { return (elements[0].geturl());// first URL from Google } else { return ("No results."); } } catch(exception e) { return ("Problem searching: " + e.getmessage()); } } // End of findcityref } M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

49 Going back to ShipFast.com Application integration using SOAP as a common message format. KennyCD.com Customer KennyCD.com Customer TomBooks.com Customer Internet KennyCD.com Site Business System (.NET) TomBooks.com Site Business System (PHP) Some Other Site SOAP/HTML Internet SOAP/HTML SOAP/HTML ShipFast.com Business System (J2EE) Business System (J2EE) M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

50 Web2.0 Defining Web 2.0 (Tim O Reilly, Web 2.0 is about using the Web as platform for: delivering software as a continually-updated service that gets better the more people use it, consuming and remixing data from multiple sources, including individual users, while providing their own data and services in a form that allows remixing by others, creating network effects through an architecture of participation, and going beyond the page metaphor of Web 1.0 to deliver rich user experiences e.g., Web 1.0 Web 2.0 DoubleClick Google AdSense Ofoto Flickr Britannica Online Wikipedia personal websites blogging screen scraping web services M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

51 Mashup Mashup is one of the good examples of Web2.0 in action... A Web application building technique that combines content from more than one source into an integrated experience Frequently implemented with Ajax from existing Web services (Google, Google Maps, Yahoo, Flickr, YouTube, etc.) Users can mix many services for unexpected/creative usages M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

52 Mashup - examples - Uses Google Map API and Property Data M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

53 Mashup This mashup uses APIs from: Amazon ecommerce, Flickr, Yahoo Search, Yahoo Term Extraction M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

54 Mashup APIs: Grouper Video + Yahoo Video Search + YouTube M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55

55 Mashup Widgets or M. C. Barukh, H. Paik (CSE, UNSW) COMP9321, 15s1 Week / 55