Web Services
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This document provides an overview of web services, including RESTful and SOAP-based services. It discusses key concepts such as APIs, URIs, HTTP methods, XML/JSON data formats. For RESTful services, it covers the main design principles of being stateless, using explicit HTTP methods, and having directory-like URIs. For SOAP-based services, it describes the roles of SOAP, WSDL, and UDDI in defining and discovering services. The document also provides examples and comparisons of RESTful and SOAP-based approaches.
Web Services
- 1. Web Services Web Technology - 2ID60 26 November 2013 Katrien Verbert Natasha Stash George Fletcher
- 2. Plan for today • • • • • • Recap: Web fundamentals APIs, Web Services Restful services SOAP-based services Comparison Tutorial • JAX-WS: Building SOAP-based services in Java • JAX-RS: Building RESTful services in Java PAGE 4
- 3. Recap: Web Fundamentals Key Architectural Components • Identification: URI • Interaction: HTTP • Standardized Document Formats: HTML, XML, JSON, etc. PAGE 5
- 4. URIs / resources • URIs identify interesting things • documents on the Web • relevant aspects of a data set • HTTP URIs name and address resources in Web based systems • a URI names and identifies one resource • a resource can have more than one name − http://foo.com/software/latest − http://foo.com/software/v1.4 PAGE 6
- 6. Plan for today • • • • • • Recap: Web fundamentals APIs, Web Services RESTful services SOAP-based services Comparison Tutorial • JAX-WS: Building SOAP-based services in Java • JAX-RS: Building RESTful services in Java PAGE 8
- 7. APIs What is an API? and Why do we need APIs? PAGE 9
- 8. (Web) APIs • Application Programming Interface • Specifies how software components communicate with each other • e.g., Java API, 3rd party library APIs • usually come with documentation • Web API: specify how applications communicate with other over the Web (HTTP, URI, XML, etc.) PAGE 10
- 9. Web Services, Web Applications and APIs (Application Programming Interface) • Web Applications == Web Services == Web APIs ? PAGE 11
- 10. Web Services, Web Applications and APIs (Application Programming Interface) • Web Applications are designed to be accessed by end users through Web client software • Web Services are intended to be used by other software applications • Web APIs ≈ Web Services PAGE 12
- 11. Web Services • “Web Services” “Web APIs” • Build on the design principles and architectural components of the Web • Provide certain operations • Exchange structured data in standard formats (JSON, XML, etc.) PAGE 13
- 12. Web Services Example operations: • Publish image on Flickr • Order a book at Amazon • Post a message on your friend’s Facebook wall PAGE 14
- 13. What Are Web Services? PAGE 15
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- 17. What Are Web Services? • W3C definition: • A software system designed to support interoperable machine-to-machine interaction over a network... PAGE 19
- 18. Web Services Use • Connect existing software • Reusable application components PAGE 20
- 19. Major classes of Web Services • Big Web Services (L. Richardson and S. Ruby) • RESTful (REST-compliant) Web Services PAGE 21
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- 22. Overview • • • • • Introduction RESTful services SOAP-based services Comparison Tutorial • JAX-WS: Building SOAP-based services in Java • JAX-RS: Building RESTful services in Java PAGE 24
- 23. A RESTful Web service... • ... exposes its data and functionality through interlinked Web resources identified by URI. • ... is more data-centric, and less functionality-centric (as opposed to SOAP services). • ... embeds functionality of the service in the uniform HTTP interfaces for interaction: GET, PUT, DELETE, POST. • ... uses HTTP as the application protocol instead of SOAP PAGE 25
- 24. Four basic design principles • • • • Use HTTP methods explicitly. Be stateless. Expose directory structure-like URIs. Transfer XML, JavaScript Object Notation (JSON), or both. PAGE 26
- 25. Use HTTP methods explicitly • One-to-one mapping between • create, read, update, and delete (CRUD) operations • and HTTP methods. • According to this mapping: • • • • To create a resource on the server, use POST. To retrieve a resource, use GET. To change the state of a resource or to update it, use PUT. To remove or delete a resource, use DELETE. PAGE 27
- 26. Example: HTTP GET request GET /users/Robert HTTP/1.1 Host: myserver Accept: application/xml PAGE 28
- 27. Example: HTTP PUT request PUT /users/Robert HTTP/1.1 Host: myserver Content-Type: application/xml <?xml version="1.0"?> <user> <name>Bob</name> </user> PAGE 29
- 28. Be stateless Stateful design Stateless design PAGE 30
- 29. Expose directory structure-like URIs http://www.myservice.org/discussion/topics/{topic} http://www.myservice.org/discussion/{year}/{day}/{month}/{topic} http://www.myservice.org/discussion/2008/12/10/{topic} PAGE 31
- 30. Transfer XML, JSON, or both <?xml version="1.0"?> <discussion date="{date}" topic="{topic}"> <comment>{comment}</comment> <replies> <reply from="joe@mail.com" href="/discussion/topics/{topic}/joe"/> <reply from="bob@mail.com" href="/discussion/topics/{topic}/bob"/> </replies> </discussion> PAGE 32
- 31. Tools and frameworks • Ruby on Rails -- a framework for building RESTful Web applications – http://www.rubyonrails.org/ • Restlet -- framework for mapping REST concepts to Java classes http://www.restlet.org • Django - framework for building RESTful Web applications in Python • JAX-RC specification (http://jsr311.java.net/) -provides a Java API for RESTful Web Services over the HTTP • RESTEasy (http://www.jboss.org/resteasy/) - Jboss project that provides various frameworks for building RESTful Web Services and RESTful Java applications. PAGE 33
- 32. Overview • • • • • Introduction Restful services Big web services Comparison Tutorial • JAX-WS: Building SOAP-based services in Java • JAX-RS: Building RESTful services in Java PAGE 34
- 33. Big web services • SOAP (Simple Object Access Protocol) • WSDL (Web Services Description Language) • UDDI (Universal Description, Discovery, and Integration) PAGE 35
- 35. What is SOAP • • • • • • • SOAP used to stand for Simple Object Access Protocol SOAP is a communication protocol SOAP is designed to communicate via Internet SOAP is based on XML SOAP is simple and extensible SOAP is platform and language independent SOAP is a W3C standard PAGE 37
- 36. SOAP Message Structure SOAP Envelope SOAP Header header block SOAP Body body block <?xml version='1.0' ?><env:Envelope xmlns:env=" http://www.w3.org/2003/05/soap-envelope"> <env:Header> ... </env:Header> <env:Body> ... <env:Fault> ... </env:Fault> </env:Body> </env:Envelope> PAGE 38
- 37. SOAP Example: RPC-Style Request Message <?xml version='1.0' ?> <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"> <env:Body> <ts:getPrice xmlns:ts="http://travelagency.example.org/wsdl/trips" s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding"> <ts:departing>Amsterdam (Schiphol)</ts:departing> <ts:arriving>Saint-Petersburg (Pulkovo)</ts:arriving> <ts:departureDate>01-05-2010</ts:departureDate> <ts:/getPrice> </env:Body> </env:Envelope> Request <?xml version='1.0' ?><env:Envelope xmlns:env=" Response http://www.w3.org/2003/05/soap-envelope"> <env:Body> <ts:getPriceResponse xmlns:ts="http://travelagency.example.org/wsdl/trips" s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding" > <ts:price>180.00</ts:price> </ts:getPriceResponse> </env:Body> </env:Envelope> PAGE 39
- 38. SOAP HTTP Binding: SOAP HTTP Post Usage POST /pricesService/getPrice HTTP/1.1 Host: http://travelagency.example.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version='1.0' ?> <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"> <env:Body> <ts:getPrice xmlns:ts="http://travelagency.example.org/wsdl/trips"> <ts:departing>Amsterdam (Schiphol)</ts:departing> <ts:arriving>Saint-Petersburg (Pulkovo)</ts:arriving> <ts:departureDate>21-04-2010</ts:departureDate> <ts:/getPrice> </env:Body> </env:Envelope> PAGE 40
- 39. SOAP HTTP Binding: SOAP Response HTTP/1.1 200 OK Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn <?xml version='1.0' ?> <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"> <env:Body> <ts:getPriceResponse xmlns:ts="http://travelagency.example.org/wsdl/trips"> <ts:price>180.00</ts:price> </ts:getPriceResponse> </env:Body> </env:Envelope> PAGE 41
- 41. What is WSDL • • • • WSDL stands for Web Services Description Language WSDL is used to describe and locate Web Services WSDL is based on XML WSDL is a W3C standard PAGE 43
- 42. WSDL • Describes three fundamental properties • What a service does • • How a service is accessed • • Operations (methods) provided by the service Data format and protocol details Where a service is located • Address (URL) details PAGE 44
- 43. WSDL Document Structure WSDL Specification abstract part types messages operations Main structure of WSDL document <definitions targerNamespace= ... > <types>definition of types...</types> <message>definition of a message...</message> port types <portType>definition of a port</portType> concrete part bindings service port <binding>definition of a binding...</binding> <service> <port>...</port> </service> </definitions> PAGE 45
- 44. WSDL Document Example: Abstract Part <message name="itineraryMsg"> <part name="departing" type="xs:string"/> <part name="arriving" type="xs:string"/> <part name="departureDate" type="xs:date"/> </message> <message name="itineraryRespMsg"> <part name="price" type="xs:string"/> </message> <portType name="pricesPT"> <operation name="getPrice"> <input message="itineraryMsg"/> <output message="itineraryRespMsg"/> </operation> </portType> PAGE 46
- 45. Operation Types Type Definition One-way The operation can receive a message but will not return a response Requestresponse The operation can receive a request and will return a response Solicit-response The operation can send a request and will wait for a response Notification The operation can send a message but will not wait for a response PAGE 47
- 46. Example: One-Way Operation <message name="newPrices"> <part name="departing" type="xs:string"/> <part name="arriving" type="xs:string"/> <part name="departureDate" type="xs:date"/> <part name="price" type="xs:string"/> </message> <portType name="pricesPT"> ... <operation name="setPrice"> <input message="newPrices"/> </operation> </portType > PAGE 48
- 47. WSDL Document Example: Concrete Part <service name="pricesService"> <port name="getPriceRPCPort" binding="ts:b1"> <soap:address location="http://travelagency.example.org/pricesService"> </port> </service> xmlns:ts='http://travelagency.example.org/wsdl/trips' PAGE 49
- 49. What is UDDI • UDDI stands for Universal Description, Discovery and Integration • UDDI a standard for publishing and discovering Web services • UDDI is a specification for a distributed registry of Web services • UDDI is built upon standards such as HTTP, XML, XML Schema, SOAP, WSDL • UDDI can communicate via SOAP, CORBA, Java RMI Protocol • UDDI uses WSDL to describe interfaces to Web Services PAGE 51
- 50. Ways to Use UDDI Registry • White pages – name, address, contact person, Web site • Yellow pages – types of business, locations, products, services, categorizations • Green pages – technical information about business services, pointers to WSDL descriptions of the services PAGE 52
- 51. UDDI Data Model: UDDI Core Data Types Example: http://www.tutorialspoint.com/uddi/uddi_data_model.htm PAGE 53
- 52. UDDI Data Model: tModel example <?xml version="1.0"?> <tModel tModelKey="”> <name>http://www.getquote.com/StockQuoteService-interface</name> <description xml:lang="en">…</description> <overviewDoc> <description xml:lang="en”>WSDL Service Interface Document </description> <overviewURL> http://www.getquote.com/services/SQSinterface.wsdl#SingleSymbolBinding </overviewURL> </overviewDoc> <categoryBag> <keyedReference tModelKey="UUID:C1ACF26D-9672-4404-9D70-39B756E62AB4” keyName="uddi-org:types" keyValue="wsdlSpec"/> <keyedReference tModelKey="UUID:DB77450D-9FA8-45D4-A7BC-04411D14E384” keyName="Stock market trading services” keyValue="84121801"/> </categoryBag> </tModel> PAGE 54
- 53. UDDI: Programmatic Interfaces • UDDI Inquiry Interface: – find_business, find_service, find_tModel, find_binding, find_relatedBusiness – get_businessDetail, get_serviceDetail, get_bindingDetail, get_tModelDetail • UDDI Publisher Interface: – save_business, save_service, save_binding, save_tModel – delete_business, delete_service, delete_binding, delete_tModel – ...! PAGE 55
- 54. Big Web Services Examples • http://www.xmethods.com • http://www.programmableweb.com/ PAGE 56
- 55. Web services enable 1. 2. 3. 4. data exchange between various applications and different platforms to resolve interoperability issues applications to function between two different operating systems server all of the above PAGE 57
- 56. Which of the following is used to locate and describe web services? 1. 2. 3. 4. SOAP Web page WSDL UDDI PAGE 58
- 57. Overview • • • • • Introduction Restful services SOAP-based services Comparison Tutorial • JAX-WS: Building SOAP-based services in Java • JAX-RS: Building RESTful services in Java PAGE 59
- 58. Big Web Service Operations vs RESTful Web Service URIs Big WS operations RESTful WS URIs getAllUsers() http://example.com/users/ " getUserById(String id) http://example.com/users/id/{user-id} getUserByName(…), addUser(…) removeUser(…), updateUser(…) http://example.com/users/name/{user-name} PAGE 60
- 59. Big Web Services versus REST • A SOAP service has a single endpoint • that handles all the operations • therefore it has to have an application-specific interface. • A RESTful service has a number of resources • so the operations can be distributed onto the resources • and mapped to a small uniform set of operations. PAGE 61
- 60. Comparison: Big Web Services vs RESTful Web Services • Big Web Services pros: – protocol transparency and independence – existence of tools to hide the complexity – security • Big Web Services cons: – – – – – rudimentary processing protocol complexity heavyweight architecture do not get the benefits of resource-oriented services opaqueness PAGE 62
- 61. Comparison: Big Web Services vs RESTful Web Services • RESTful Web Services pros: – – – – – – simplicity lightweight infrastructure addressability uniform interface scalability of stateless RESTful Web Service improved performance using JSON • RESTful Web Services cons: – – – – bound to one protocol: HTTP only POST and GET can be used in XHTML form dealing with large input data - malformed URI security issues PAGE 63
- 62. Sources • Cesare Pautasso,Olaf Zimmermann,Frank Leymann (2008) RESTful Web Services vs. Big Web Services: Making the Right Architectural Decision. Proc. of the 17th International World Wide Web Conference (WWW2008), Bejing, China, April 2008. • Alex Rodriguez. (2008). RESTful Web services: The basics. Available at: http://www.ibm.com/developerworks/webservices/library/wsrestful/ • Cesare Pautasso and Erik Wilde. Design Principles, Patterns and Emerging Technologies for RESTful Web Services. http://dret.net/netdret/docs/rest-icwe2010/ • Bernhard Hasl. RESTful web service APIs http://courses2.cit.cornell.edu/info4302_2012fa/lectures/week7/ INFO_CS4302_Lecture12.pdf PAGE 64