02267: Software Development of Web Services

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1 02267: Software Development of Web Services Week 1 Hubert Baumeister huba@dtu.dk Department of Applied Mathematics and Computer Science Technical University of Denmark Fall 2013

2 Contents Course Introduction Course Goal Practical Information Distributed IT Service Oriented Architecture Web Services

3 What is this Course About? Web Services & Service Oriented Architecture 5 ECTS points Complementary courses 02221/02222 on distributed systems

4 Goals of this course Knowledge about What are Web services and Service-Oriented Architecture (SOA) Technologies and standards for Web services e.g. XML, SOAP, WSDL,... Web service extensions Able to evaluate When to use Web services and SOA What are the problems when using Web services and what are possible solutions Able to do Implementation of Web services (simple and composite) including writing of XML Schema documents (XSD), WSDL, BPEL

5 Topics not addressed in this course Web services are basically a computer to computer technology using technologies also used with Web applications Therefore, the following topics won t be addressed in this course HTML, Content Management Systems, JSON, Javascript, JSP, ASP, Python, Perl, How servelets work, MS-Sharepoint, API s for social networking (i.e. OpenSocial) or location aware services, OAuth Other topics not addressed in the course Connection to databases (e.g. JDBC), Programming languages like Java or C#

6 Course Prerequisites Programming language: Java Operating system knowledge Examples and exercises use Unix (Linux / FreeBSD) or Windows Software needs to be installed Shell commands; Shell-scripts need to be written or adapted Basic knowledge of Internet technologies: XML, HTML, Sockets, TCP,...

7 Practical Information I Workload: 5ECTS = 9 hours / week 90min lecture (2 * 45min + 10min break) 90min tutoring sessions 5 hours self study Additional reading tasks You need to work on the exercises outside of the tutoring sessions Lectures 8:30 10:15 on Monday Tutoring sessions 10:15 12:00 in E-Databar: Rooms 003 and 015 in Building 341 Exercises are not mandatory but help prepare for the exam project

8 Practical Information II How to reach me Room: 303B/058 Course Web Page Software Java 6/7 (JDK), OpenESB 2.3 (Netbeans (IDE) and Glassfish (Application Server))

9 Grading 1. Project work 5 weeks (week 44 49) Teams of 4 6 (Team building week 44 (participation is mandatory)) Implementing Web services (simple and composite) Writing a report 2. Project presentation by the project teams Project presentation ( 10min) + questions: total 45 min Dates Monday Wednesday week 51 ( )

10 Literature Michael P. Papazoglou, Web services: Principles and Technolgoy, Pearson Education Limited, 2008 plus additional literature throughout the course

11 Example: Purchase Order The customer wants to purchase some goods (via the Internet) 1. Customer contacts the supplier and orders the goods 2. Sales department check with credit card department if credit is okay 3. Sales department check with inventory department if the goods are on stock 4. Sales department informs the billing department to bill the customer 5. Sales department informs the shipment department to send out the goods 6. Shipment department sends the goods to customer 7. Shipment department informs the billing department to send the invoice 8. Billing department sends the invoice to the customer

12 Classical distributed IT (I) Purchase order is a business process involving different IT systems Components in an IT infrastructure Legacy systems Application server Database server Web server Clients: Web browser, thin client, fat client Goal Automation of business processes Business processes span all of these systems Different IT system use different technologies How to connect all these parts in a uniform way technically and semantically?

13 Classical distributed IT (II) Problems Different technologies CORBA, EJB,.NET, COM/DCOM No well defined interfaces Ad-hoc combination

14 Classical distributed IT (III) Solution Unifying view representing IT to the outside IT world Service-Oriented Architecture (SOA) Use Internet standards Web service

15 Example: Purchase Order II The customer wants to purchase some goods (via the Internet) 1. Customer contacts the supplier s Web site and orders the goods 2. The Web site uses the process sales service to actually order the goods 3. The process sales service contacts the credit card service to check the customer s credit 4. The process sales service calls the check inventory service to check if the goods are on stock...

16 Example: Purchase Order III The IT systems of each department offer services simple (Web) services The purchase order business process is itself a service offered to the customer which uses the services of the other IT systems composite (Web) service

17 Global Computing Challenge (I) IT integration between IT systems of different companies Business to Business Loose coupling In addition to the problems of a distributed IT infrastructure: Firewalls: block most of TCP/IP ports for security reasons

18 SOA (Service Oriented Architecture) Automate business processes within a company across companies Services (SOA) Web standards (e.g. XML, HTTP,... )

19 Service-Oriented Architecture (SOA) A set of principles for organising the software Not restricted to the use of Web services Web services OSGi services Grid services Cloud services...

20 SOA Principles (I) Loose coupling Services represent self contained units of logic (one function or a set of functions) which are relatively independent Resusability Discoverablity :Service Registry :Client :Service Provider

21 SOA Principles (II) Abstract service description (independent of implementation) Encapsulation (autonomy and abstraction) Compositionality And additional for Web services Based on open standards Vendor neutral / vendor diversity

22 Service invocation vs. function call Function call Within the same process Function is always available Takes almost no time Focus on single calls Service invocation Across processes, computers, networks Takes time (several magnitudes more than a function call) May fail Several service invocation may form a dialog

23 Service invocation vs. function call Function call Within the same process Function is always available Takes almost no time Focus on single calls Fine grained Tight coupling Simple data as parameters Service invocation Across processes, computers, networks Takes time (several magnitudes more than a function call) May fail Several service invocation may form a dialog Coarse grained Loosely coupled Complex data, documents, as parameters

24 Web Services Solutions for the global computing problem Firewalls Communication via HTTP using XML messages SOAP Different technologies n interfaces (x, y Web services) instead of n 2 for x y. Use of Internet standards

25 Integration Scenario

26 Basic idea of Web services Exchange of messages Messages are encoded using XML SOAP Using standard protocols to transport messages HTTP, SMTP,... Message can be sent: One-way: Call the service, but don t expect an immediate answer asynchronous messaging Request / response: Call the service and wait for the response most common style synchronous messaging

27 The history of Web services Internet (70 s, 80 s) Web (90 s) Extensible Markup Language (XML) (98) Simple Object Access Protocol (SOAP) (2000) Description of the REST architecture principle behind the HTTP protocol (Roy Fielding) (2000) Web Service Description Language (WSDL) (2001)

28 Success of Web services... SOAP is based on XML SOAP messages have a simple structure: <soapenv:envelope> <soapenv:body> <ns1:srrequest> <ns1:action>register</ns1:action> <ns1:student> <ns1:name>søren Helmersen</ns1:name> </ns1:student> </ns1:srrequest> </soapenv:body> </soapenv:envelope> SOAP messages are transported by HTTP or SMTP

29 ... Consequences... It is easy to generate SOAP messages Only a XML parser is needed for parsing the messages Web server technology can be reused for Web services (e.g. cgi-bins and servlets) Easy to provide Web services in any programming language Easy to use Web services in any programming language and operating system

30 ... But Message contents / data encoding is not standardised WSDL and XML Schema help with that Simple messageing model: Support needed, e.g., for Security Meta information (Authorization, Authentification, Dialogs,... )...

31 Demo: A simple Web service 1. Creating a simple HelloWorld Web service in Java prepending Hello to its input 2. Deploying the Web service on a Web server (GlassFish) 3. Calling the Web service from Java 4. Calling the Web service from Ruby

32 What we are going to study in this course Message structure: SOAP Description of Web services: WSDL (Web Service Description Language) week01/wsdl.wsdl Discovery of Web services: UDDI (Universial Description, Discovery, and Integration), WSIL (Web Service Inspection Language)

33 Web service composition and... How is a Web service constructed from others Issues Long running business processes Transaction: What to do when something goes wrong Compensation Handler

34 ... Web service coordination How do different Web services play together Planned Orchestration Web service Composition Ad-hoc: Each participant has to follow rules Choreography

35 Security Problem: In principle SOAP messages can be read by anybody and modified by anyone One possibility is that the transport layer ensures privacy and authenticy HTTPS Other possibility: SOAP message itself contains security features WS-Security Message parts can be encrypted Message parts can be signed week01/security.xml What parts need to be encrypted and signed? Other security properties: Trust,...

36 WS-* Standards: Addressing, Reliable Messaging,Policy,... There are hundreds of standards addressing shortcomings of the simple WS model Addressing SOAP messages itself do not contain information about to whom the message is addressed or from whom the message is sent Reliable Messaging Reliability depends partly on the transport protocol (e.g. HTTP partly reliable, SMTP not reliable: messages can be lost) Policy What properties has a Web service: Performance, Cost, support for WS-security, WS-Addressing, e.t.c.

37 Contents of the course 1. Introduction to Web services and SOA 2. Basic technologies: XML, XML Schema, Basic Web service technology: SOAP, Describing Web services: WSDL 5. Development of Web Services: Bottom up, top down development, generating compositions from coordinations, Finding Web services: UDDI, WSIL, RESTful Web services 8. Composing Web services: BPEL 9. Coordinating Web services: WS-Coordination, WS-CDL,... Long running transactions: WS-AtomicTransaction, Compensation, Security: WS-Security,......

02267: Software Development of Web Services

02267: Software Development of Web Services Week 1 Hubert Baumeister huba@dtu.dk Department of Applied Mathematics and Computer Science Technical University of Denmark Fall 2016 1 Contents Why Services?