MTAT Enterprise System Integration. Lecture 3: Web Services SOAP & REST

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1 MTAT Enterprise System Integration Lecture 3: Web Services SOAP & REST Luciano García Bañuelos luciano.garcia ät ut.ee

2 Web Services Web services is an effort to build a distributed computing platform for the Web. Goals Enable universal interoperability. Widespread adoption, ubiquity: All major industrial actors are involved Supported also by academic actors 2

3 WS: Architectural principles Organization/Querying UDDI Service directory Discovery Advertisement Service description WSDL? Consumer Binding & Invocation Interaction SOAP Service provider 3

Invocation Description Organization/Querying WSDL UDDI

4 Web Services stack Composition Ad hoc aggregation Orchestration WS-BPEL Choreography WS-CDL Advertisement & discovery Binding & Invocation Description Organization/Querying WSDL UDDI Interaction SOAP XML encoding Transport Sync: HTTP, FTP Async: SMTP,JMS 4

5 RPC: Elements of implementation Call Execution Return Client Service 5

6 RPC: Elements of implementation Call Param msg marshalling Param msg unmarshalling Block Return Resume Result msg unmarshalling Activate Result marshalling Client Result msg reception Param msg sending Param msg reception Result msg sending Service 6

7 WSDL Acronym for Web Service Definition Language XML-based, extensible language for: Describing service interfaces Specifying binding details ð In a platform-independent way Emerged as a de facto standard, now endorsed by the W3C 7

8 WSDL document <definitions> <types> definition of types... </types> <message> definition of messages... </message> Abstract Description <porttype> <operation>... </operation> <operation>... </operation> </porttype> <binding> definition of bindings... </binding> <service> <port>... </port> <port>... </port> </service> </definitions> Grounding Description 8

9 WSDL elements porttype operation inmessage outmessage SOAP stub Port (e.g. Binding SOAP Service CORBA stub Port Binding IIOP 9

10 WSDL: Types and Messages WSDL Example <definitions name="sales" targetnamespace=" xmlns=" xmlns:salesx=" <import namespace=" location="salesx.xsd"/> <message name="rfqmsg"> <part name="payload" element="salesx:rfq"/> </message> <message name="quotemsg"> <part name="payload" element="salesx:quote"/> </message> <message name="ordermsg"> <part name="payload" element="salesx:order"/> </message> <message name="cancelordermsg"> <part name="payload" element="salesx:cancelorder"/> </message> <message name="rejectrfqmsg"> <part name="payload" element="salesx:rejectrfq"/> </message> Imported Schema 10

11 WSDL: PortTypes and Operations WSDL Example <porttype name="providerpt"> <operation name="rfq"> <input message="tns:rfqmsg"/> One-way Operation </operation> <operation name="order"> <input message="tns:ordermsg"/> </operation> <operation name="cancelorder"> <input message="tns:cancelordermsg"/> Two-Way Operation, also with fault </operation> </porttype> <operation name="rfq"> <input message="tns:rfqmsg"/> <porttype name="requesterpt"> <operation name="quote"> <output message="tns:rfqackmsg"/> <input message="tns:quotemsg"/> <fault name="cannotunderstandrfq" message="tns:rfqfaultmsg"/> </operation> <operation name="rejectrfq"> </operation> <input message="tns:rejectrfqmsg"/> </operation> </porttype> 11

12 WSDL: Bindings WSDL Example <binding name="providerptbinding" type="tns:providerpt"> <soap:binding style="document" transport=" <operation name="rfq"> <soap:operation style="document" soapaction="rfq"/> <input> <soap:header message="tns:replytoheader" part="replyto" use="literal"/> <soap:header message="tns:messageidheader" part="messageid use="literal"/> <soap:body use="literal"/> </input> </operation>... </soap:binding> </binding> 12

13 WSDL: Services WSDL Example <service name="salesbp"> <port name="providerptport" binding="tns:providerptbinding"> <soap:address location=" </port> URI where the provider is accessible </service> <service name="requesterptservice"> <port name="requesterptport" binding="tns:requesterptbinding"> <soap:address location=" </port> </service>... </definitions> The requester s location is set on the fly in the SOAP header 13

14 Developing Web Services using WSDL Contract-first: WSDL wsdl2java wsdl.exe Application dependent Application dependent Marshalling/ Unmarshalling (SOAP msg) Marshalling/ Unmarshalling (SOAP msg) Client (Java) Application independent Communication middleware Application independent Communication middleware Service (C#) 14

15 Developing Web Services using WSDL Application-first: WSDL wsimport wsgen Application dependent Marshalling/ Unmarshalling (SOAP msg) Application dependent Marshalling/ Unmarshalling (SOAP msg) Java application with annotations Client (Java) Application independent Communication middleware Application independent Communication middleware Service (Java) 15

Example: Web Service @WebService public class ItemDAOwsdl { @EJB ItemDAO itemdao; Hint: Implement the web service as a façade for your business logic @WebMethod

16 Example: Web public class ItemDAOwsdl ItemDAO itemdao; Hint: Implement the web service as a façade for your business public List<Item> getallitems() { return itemdao.getallitems(); public Item getitem(@webparam(name = "id") int id) { return itemdao.getitem(id); } 16

Example: Web Service Client public static void main(string[] args) throws Exception { ItemDAOwsdlServiceLocator a = new ItemDAOwsdlServiceLocator();

17 Example: Web Service Client public static void main(string[] args) throws Exception { ItemDAOwsdlServiceLocator a = new ItemDAOwsdlServiceLocator(); ItemDAOwsdl w = a.getitemdaowsdlport(); List<Item> list = w.getallitems(); for (Item i : list) System.out.println(i.getColor() + " as a " + i.getname()); } 17

18 WS-* in Action (runtime) Phase 1 Serialize (obj > XML) XML SOAP request XML Phase 2 Deserialize (XML > obj) SOAP message SOAP message Requester Provider Proxy object Web XML Web service object Client Web Server XML XML Phase 4 Deserialize (XML > obj) SOAP message SOAP response SOAP message Phase 3 Serialize (obj > XML) 18

19 SOAP Used to be Simple Object Access Protocol, but no longer an acronym SOAP envelope: <Envelope xmlns=" envelope"> <Header>...</Header> <Body>...</Body> </Envelope> 19

20 Example 1 <env:envelope xmlns:env=" envelope" xmlns:w=" xmlns:n=" <env:header> <w:ticket>54b42cf401a</w:ticket> <n:token> <n:value> </n:value> <n:issuer> </n:token> </env:header> <env:body> <w:buy> <w:product>light gadget</w:product> <w:amount>430</w:amount> </w:buy> </env:body> </env:envelope> 20

21 Envelope Headers Encryption information Access control Routing Auditing Data extensions INITIAL SENDER INTERMEDIARY INTERMEDIARY INTERMEDIARY ULTIMATE RECEIVER 21

22 Example 1 <env:envelope xmlns:env=" envelope" xmlns:c=" xmlns:c=" <env:header> <c:encoding env:role=" env:mustunderstand="true"> gzip+base64 </c:encoding> <r:route env:relay="true" env:role=" envelope/role/next"> <r:node> </r:node> <r:node> </r:node> </r:route> </env:header> <env:body> H4sICACI/0EAA3EA80jNycnXUSjPL8pJUeQCABinVXsOAAAA </env:body> </env:envelope> 22

23 SOAP data encoding name Zacharias Doe Jane Dow name spouse spouse father name John Doe mother father family name Jack Doe 23

24 SOAP data encoding (cont.) <family xmlns:env=" envelope" xmlns:enc=" encoding" env:encodingstyle=" encoding" xmlns=" <name>jack Doe</name> <father enc:id="1"> <name>john Doe</name> <father> <name>zacharias Doe</name> </father> <spouse enc:ref="2"/> </father> <mother enc:id="2"> <name>jane Dow</name> <spouse enc:ref="1"/> </mother> </family> 24

25 WSDL & SOAP Bindings RPC Request/Response model Body contains one element named after the operation Document Payload semantics Partners decide upon XSD of the message being exchanged Encodings Encoded Data encoding explicitly specified in the message exchanged Data types explicitly specified Literal Only values are included RPC/Encoded RPC/Literal Document/Encoded Document/Literal 25

26 Examples <soap:envelope> <soap:body> <mymethod> <x xsi:type="xsd:int">5</x> <y xsi:type="xsd:float">5.0</y> </mymethod> </soap:body> </soap:envelope> Document/literal RPC/encoded <soap:envelope> <soap:body> <xelement>5</xelement> <yelement>5.0</yelement> </soap:body> </soap:envelope> 26

27 Additional WS-* Specifications WS-Addressing: Defines SOAP headers for: Including sender, return addresses and message IDs Including references to related messages (can be useful to relate a request and a reply) WS-Security: Defines extensions to SOAP for: propagation of security tokens which securely identify and authenticate clients, message integrity via XML Signature, message confidentially via XML Encryption. WS-ReliableMessaging Extensions for reliable delivery of messages (exactly-once delivery) 27

28 REST Acronym for Representational State Transfer Introduced/defined in 2000 by Roy Fielding in his Doctoral Dissertation BTW, Fielding is one of the principal authors of HTTP specification versions 1.0 and 1.1 REST is an architectural style The Web is an example of a distributed system using this style REST is NOT a standard NOR a product (e.g. Web Framework) 28

29 Why the Web architecture (REST)? Scalable Fault-tolerant Recoverable Secure Loosely coupled Precisely the set of characteristics we would like to see in Enterprise Software Systems! 29

30 Web Fundamentals To embrace the Web, we need to understand how it works The Web is a distributed hypermedia model It doesn t try to hide that distribution from you! Our challenge: Figure out the mapping between our problem domain and the underlying Web platform 30

31 Richardson Maturity Framework What are the (conceptual) components of the Web? Hypermedia HTTP URI Interaction model Traversal of hyperlinks Interaction protocol Methods: GET, POST, PUT, DELETE, etc. Status codes: 200 Ok, 404 Not found, etc. Resource identifier e.g., Representational_State_Transfer 31

Status Codes } 1xx - Metadata } 2xx Everything s fine } 3xx

32 Richardson s Maturity Level 2 Multiple URIs, multiple HTTP verbs, and HTTP Status Codes } HTTP verbs } GET, POST, PUT, DELETE } HTTP Status Codes } 1xx - Metadata } 2xx Everything s fine } 3xx Redirection } 4xx Client did something wrong } 5xx Server did a bad thing 32

33 CRUD Resource Lifecycle The resource is created with POST It s read with GET And updated via PUT Finally it s removed using DELETE 33

Read with GET GET /orders/1234 200 OK <order /> Ordering

34 Read with GET GET /orders/ OK <order /> Ordering Client 404 Not Found Ordering Service 500 Internal Error 34

GET JAX-RS Implementation @Path("/") public class OrderingService { @GET @Produces( application/xml")

getDatabase().getOrder(orderId); if (order!= null) { return xstream.

35 GET JAX-RS public class public String getorder(@pathparam("orderid") String orderid) { try { Order order = OrderDatabase.getDatabase().getOrder(orderId); if (order!= null) { return xstream.toxml(order); } else { throw new WebApplicationException(404); } } catch (Exception e) { throw new WebApplicationException(500); } } // Remainder of implementation omitted for brevity } 35

36 Acknowledgements My slides are based on material by Møller & Schwatzbach Jim Webber ( Sam Guinea (polimi) Text books An introduction to XML and Web Technologies Møller & Schwatzbach, Addison-Wesley 2006 REST In Practice ( Jim Webber, Savas Parastatidis, and Ian S. Robinson O Reilly Media

MTAT Enterprise System Integration

MTAT Enterprise System Integration MTAT.03.229 Enterprise System Integration Lecture 10: WSDL/SOAP Web services Luciano García-Bañuelos University of Tartu The picture Enterpriseso2ware Presenta,on Presenta,on Integra,onlayer Applica,onlogic