1. 1/30/20161 Introduction to Web Services Bina Ramamurthy bina@cse.buffalo.edu

2. 1/30/20162 Topics for Discussion HTTP : Hyper Text Transfer Protocol HTML: Hyper Text Markup Language XML: eXtensible Markup Language Resource references on the web Web services SOAP: Simple Object Request Protocol REST: Representational State Transfer Summary

3. HTTP Protocol for communication among web entities. It is a standard from IETF (Internet Engineering Task Force) and W3C: (World Wide Web Consortium) Request-response model for client-server systems HTTP operates by sending requests with operations to be performed on resources referred by Uniform Resource Identifiers (URI) Request methods are: HEAD, GET, POST, PUT, DELETE, TRACE,… PATCH (just a few standard commands) 1/30/20163

4. HTML Hyper text mark-up language Standard markups for structural organization of web pages Example: File System FileSys FileSystemOct21.ppt 1/30/20164

5. HTML over HTTP 1/30/20165 Web Browser Web server http://www.cse.buffalo.edu/faculty/bina Web Browser Request: Get http:… Response: index.html browser interpretation of index.html

6. 1/30/20166 XML XML is a markup language, developed by W3C (World Wide Web Consortium), mainly to overcome the limitations of HTML. But it took a life of its own and has become a very popular part of distributed systems. We will examine its definition, associated specifications (DTD, XSLT etc.), Java APIs available to process XML, protocols and services based on XML, and the role XML plays in a distributed computing environment.

7. 1/30/20167 First Look at XML It has no predefined tags. Such as in HTML Domains may specify their own set of standard tags It is stricter. Most html document have errors and the browser have to built to take care of these. On the other hand XML has a strict syntax. There is a notion of validity and A notion of well-formed.

8. 1/30/20168 An Example: Memo See the two documents enclosed: one in html and the other in XML formats. Observe the meaningful tags in XML. Compare it to a class definition: it looks like a class with data definitions and accessors (tags).

9. 1/30/20169 Memo.html vs memo.xml <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"> memo.html Hello World Bina CSE486 DS Students Wake up everyone BR - Hello World bina CSE486 DS Students Wake up everyone br

10. XML SOAPXMLHTTP/OthersTCP/IPREST 1/30/201610

11. XML parsing Lets understand XML parsing. Reference: http://java.sun.com/developer/technical Articles/xml/mapping/index.html http://java.sun.com/developer/technical Articles/xml/mapping/index.html Mapping/parsing is similar to compiling: if it is not valid or well formed, the parser is going to complain Lets look at some examples starting from the very beginning. 1/30/201611

12. 1/30/201612 XML to SOAP Simple xml can facilitate sending message to receive information. The message could be operations to be performed on objects. Simple Object Access Protocol (SOAP) Representational State Transfer (REST) is an architectural pattern on HTTP’s methods

13. 1/30/201613 SOAP Request 827635

14. 1/30/201614 SOAP Reply Toptimate 3-Piece Set 827635 3-Piece luggage set. Black Polyester. 96.50 true

15. 1/30/201615 SOAP  Web Services (WS)  SOA Read this paper: http://www.w3.org/DesignIssues/WebServic es.html

16. 1/30/201616 WS Stack Network XML-based Messaging Service Description Service Publication Service Discovery Service Flow HTTP, FTP, MQ Email, IIOP SOAP WSDL UDDI WSFL Security Management Quality of Service

17. 1/30/201617 WS Interoperability Infrastructure Network XML Messaging Service Description WSDL SOAP HTTP Do you see any platform or language dependencies here?

18. 1/30/201618 Summary We looked at foundational concepts supporting web services: XML, SOAP, WSDL and Web Services standards. We also illustrated the concepts using sample programs. We will discuss REST-based web services and WDSL in the next lectures.