Co-Dependencies of Concepts

1. Co-Dependencies of Concepts CIS 340

2. What Does It Mean? CIS 340

3. What Does It Mean? CIS 340

4. Service-Orientation Principles • Reuse • Blocks of logic, mutually sought by many • Statelessness • Should not be required to manage the state of interactions • Sessions; users • “statefulness”  tight coupling • Loose coupling • Emergent property of statelessness; autonomy; abstraction • Autonomy • Bounded & focused; independence • Abstraction • External visibility == service description • May be composed • Small logics may be combined into larger ones • Does notimply forfeiture of loose coupling, autonomy, or abstraction • Discoverability • Registry of service descriptions

5. What is WSDL • Web Service Description Language. • An XML language used to describe and locate web services. • Written in XML. • Describe functionality of a web service • Specify how to access the service (binding protocol, message format, and etc.) • Not a W3C standard yet. • Version 1.1 released March 2001 • Working draft of Version 1.2 released July 2003

6. WSDL Introduction • WSDL contains information about the interfacesemantics and ‘administrivia’ of a call to a Web Service • Once you develop a Web Service you publish its description and a link to it in a UDDI repository so that potential users can find it • When someone wants to use your service, they request the WSDL file in order to find out the location of the service, the function calls and how to access them • Then they use this information in your WSDL file to form a SOAP request to the computer

7. Why Use WSDL? • WSDL uses XML to describe interfaces • Programming language independent way to do this. • So you can use (for example) C# programs to remotely invoke java programs. • Consider Web browsers and Web servers: • All web browsers work pretty well with all web sites. • You don’t care what kind of web server Amazon.com uses. • Amazon doesn’t care if you use IE, Mozilla, Konqueror, Safari, etc. • You all speak HTTP. • WSDL (and SOAP) are a generalization of this.

8. Working of WSDL (with Java)

9. Working of WSDL contd. • A client can invoke a web service using SOAP, HTTP GET/POST and MIME. • WSDL Document Structure • <definition> - Root element • <types> - Provides data type definitions • <message> - Represents the abstract definition of the data being transmitted • <portType> - Defines a set of abstract operations • <binding> - Specifies concrete protocol and data format specifications for the operations and messages defined by a particular portType • <port> - Specifies an address for a binding • <service> - Used to aggregate a set of related ports.

10. Namespace • The XML namespace prefix are used to indicate the namespace of the element being defined • All WSDL elements belong to the WSDL namespace, defined as http://schemas.xmlsoap.org/wsdl/ • For WSDL SOAP binding, http://schemas.xmlsoap.org/wsdl/soap/ • For WSDL HTTP GET and POST binding, http://schemas.xmlsoap.org/wsdl/http/ • For WSDL MIME binding, http://schemas.xmlsoap.org/wsdl/mime/

11. Service • A service groups a set of related ports together • Let is consider an example of a Web Service and the GetTemperature method as an operation on that service. <definitions name=‘weatherservice’ xmlns=‘http://schemas.xmlsoap.org/wsdl/’> <type> <xsd:schema … /> </type> <service name=‘WeatherService’ > … </service> </definitions>

12. Port • A port defines an individual endpoint by specifying a single address for a binding <port name=‘WeatherSoapPort’ binding=‘wsdlns:WeatherSoapBinding’ > <soap:address location=‘http://localhost/demos/wsdl/devx pert/weatherservice.asp’ /> </port> • Each port has a unique name and a binding attribute • A web service may be accessible on many ports • A port MUST NOT specify more than one address • A port MUST NOT specify any binding information other than address information

13. Message • A message is protocol independent • There is an input or request message, which is sent from the client to the service, and there is a output or response message, which is sent back the opposite way • Each <message> element contains one or more <part> elements. • <part> element corresponds to the parameter or a return value in the RPC call. • The part name order reflects the order of the parameters in the RPC signature.

14. Message contd. <message name=‘Weather.GetTemperature’ > <part name=‘zipcode’ type=‘xsd:string’ /> <part name=‘celsius’ type=‘xsd:boolean’ /> </message> <message name=‘Weather.GetTemperatureResponse’ > <part name=‘Result’ type=‘xsd:float’ /> </message>

15. Operations and PortType • Operation defines which message is the input and which message is the output • A collection of all operations exposed by the web service is called a portType <portType name=‘WeatherSoapPort’> <operation name=‘GetTemperature’ parameterOrder=‘zipcode celsius’> <input message=‘wsdlns:Weather.GetTemperature’ /> <output message=‘wsdlns:Weather.GetTemperatureResponse’ /> </operation> <!– other operations  </portType>

16. Operations and PortType • WSDL has four transmission primitives that an endpoint can support: • One-Way – The endpoint receives a message <wsdl:input> • Request-response – The endpoint receives a message and sends a correlated message <wsdl:input>,<wsdl:output>,<wsdl:fault> • Solicit-response – The endpoint sends a message and receives a correlated message <wsdl:output>, <wsdl:input>, <wsdl:fault> • Notification – The endpoint sends a message <wsdl:output>

17. Binding • Binding mechanism is used to attach a specific protocol, data format or structure to an abstract message , operation or endpoint • Binding MUST specify exactly one protocol • Binding MUST NOT specify address information • Extensibility elements are commonly used to specify some technology specific binding <binding name=‘WeatherSoapBinding’ type=‘wsdlns:WeatherSoapPort’ > … </binding>

18. SOAP Binding • <soap:binding> - Signifies that the binding is bound to the SOAP protocol format: Envelope, Header and Body <binding …> <soap:binding transport=“uri”? Style=“rpc|document”?> </binding> • <soap:operation> - Provides information for the document as a whole <binding …> <operation …> <soap:operation soapAction=“uri”? Style=“rpc|document”?> </operation> </binding>

19. SOAP Binding contd. • <soap:body> - Specifies how the message parts appear inside the SOAP Body element <input> <soap:body parts=“nmtokens”? use=“literal|encoded”? encodingStyle=“uri-list”? Namespace=“uri”?> </input> • <soap:fault> - Specifies the contents of the contents of the SOAP fault <fault> <soap:fault name=“nmtoken” use=“literal|encoded” encodingStyle=“uri-list”? Namespace=“uri”?> </fault>

20. SOAP binding contd. • <soap:header> and <soap:headerfault> - Allow headers to be defined that are transmitted inside the Header element of the SOAP Envelope <input> <soap:header message=“qname” part=“nmtoken” use=“literal|encoded”? encodingStyle=“uri-list”? Namespace=“uri”?> <soap:headerfault message=“qname” part=“nmtoken” use=“literal|encoded”? encodingStyle=“uri-list”? Namespace=“uri”?> </input> • <soap:address> - Used to give a port an address (a URI) <binding …> <soap:address location=“uri” /> </binding>

21. The Main Structure of WSDL <definition namespace = “http/… “> <type> xschema types </type> <message> … </message> <port> a set of operations </port> <binding> communication protocols </binding> <service> a list of binding and ports </service> <definition>

22. Types • <types> define types used in message declaration • XML Schema, DTD, and etc. • XML Schema must be supported by any vendor of WSDL conformant products.

23. <types> <schema targetNamespace="http://example.com/stockquote.xsd" xmlns="http://www.w3.org/2000/10/XMLSchema"> <element name="TradePriceRequest"> <complexType> <all> <element name="tickerSymbol" type="string“ minOccur = “1” maxOccur=“10”/> <element name = “payment”> <complexType> <choice> <element name = “account” type=“string”> <element name = “creditcard” type=“string”> </choice> </complexType> </element> </all> </complexType> </element> </schema> </types>

24. WSDL Messages • The <message> element defines the data elements of an operation. • Each messages can consist of one or more parts. The parts can be compared to the parameters of a function call in a traditional programming language.

25. <message name="GetLastTradePriceInput"> <part name="body" element="TradePriceRequest"/> </message> <message name="GetLastTradePriceOutput"> <part name="body" element="TradePrice"/> </message>

26. WSDL Ports • The <portType> element is the most important WSDL element. • It defines a web service, the operations that can be performed, and the messages that are involved. • The <port> defines the connection point to a web service, an instance of <portType>. • It can be compared to a function library (or a module, or a class) in a traditional programming language. Each operation can be compared to a function in a traditional programming language.

27. <portType name="StockQuotePortType"> <operation name="GetLastTradePrice"> <input message="tns:GetLastTradePriceInput"/> <output message="tns:GetLastTradePriceOutput"/> </operation> </portType>

28. Operation Types • The request-response type is the most common operation type, but WSDL defines four types: • One-way: The operation can receive a message but will not return a response • Request-response: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 • -- v 1.2 addition • request – multiple response …

29. One way and Notification Example <portType name=“RegisterPort"> <operation name=“register"> <input name=“customerInfo" message=“RegInfo"/> </operation> <operation name = “register Response”> <output name = “response” message=“ResponseInfo”/> </operation> </portType >

30. Binding • Binding defines how message are transmitted, and the location of the service.

31. <binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType"> <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/> <operation name="GetLastTradePrice"> <soap:operation soapAction="http://example.com/GetLastTradePrice"/> <input> <soap:body use="literal"/> </input> <output> <soap:body use="literal"/> </output> </operation> </binding>

32. <service name="StockQuoteService"> <documentation>My first service</documentation> <port name="StockQuotePort" binding="tns:StockQuoteBinding"> <soap:address location="http://example.com/stockquote"/> </port> </service>

33. A Very Simple Example: Echo public class echoService implements echoServiceInterface{ public String echo(String msg) { return msg; } public static void main(String[] args) { new echoService().echo(“hello”); } }

34. The Echo Interface /** * All implementers of this interface must * implement the echo() method. */ public interface echoServiceInterface { public String echo(String toEcho); }

35. Now Use Echo As A Remote Service • We can take the previous Java program and deploy it in Tomcat as a service. • Clients can then invoke the echo service. • WSDL tells them how to do it. • Clients don’t need to know anything about the service implementation or even language. • WSDL is the latest IDL • DCE and CORBA IDL were two older examples. C# Client WSDL SOAP(Echo “hello”) “hello” WSDL Tomcat+ Axis+Echo

36. The Main Structure of WSDL <definition namespace = “http/… “> <type> xschema types </type> <message> … </message> <port> a set of operations </port> <binding> communication protocols </binding> <service> a list of binding and ports </service> <definition>

37. What Does echoServiceInterface Look Like In WSDL? <?xml version="1.0" encoding="UTF-8" ?> <wsdl:definitions targetNamespace="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:apachesoap="http://xml.apache.org/xml-soap" xmlns:impl="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" xmlns:intf="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">   <wsdl:types /> <wsdl:message name="echoResponse">   <wsdl:part name="echoReturn" type="xsd:string" />   </wsdl:message> <wsdl:message name="echoRequest">   <wsdl:part name="in0" type="xsd:string" />   </wsdl:message> <wsdl:portType name="Echo"> - <wsdl:operation name="echo" parameterOrder="in0">   <wsdl:input message="impl:echoRequest" name="echoRequest" />   <wsdl:output message="impl:echoResponse" name="echoResponse" />   </wsdl:operation>   </wsdl:portType>

38. What Does This Look Like In WSDL? <wsdl:binding name="EchoSoapBinding" type="impl:Echo"> <wsdlsoap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http" /> <wsdl:operation name="echo">   <wsdlsoap:operation soapAction="" /> <wsdl:input name="echoRequest">   <wsdlsoap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" namespace="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" use="encoded" />   </wsdl:input> <wsdl:output name="echoResponse">   <wsdlsoap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding namespace="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" use="encoded" />   </wsdl:output>   </wsdl:operation>   </wsdl:binding> <wsdl:service name="EchoService"> <wsdl:port binding="impl:EchoSoapBinding" name="Echo">   <wsdlsoap:address location="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" />   </wsdl:port>   </wsdl:service> </wsdl:definitions>

39. Did I Write That WSDL by Hand? • Are you kidding? • It was automatically generated by axis. Most other Web service tools will do the same. • See other tutorial for generated WSDL. • We will go through the construction, though, for understanding.

40. WSDL Parts • Types • Used to define custom message types • Messages • Abstraction of request and response messages that my client and service need to communicate. • PortTypes • Contains a set of operations. • Operations organize WSDL messages. • Operation->method name, PortType->java interface • Bindings • Binds the PortType to a specific protocol (typically SOAP over http). • You can bind one PortType to several different protocols by using more than one port. • Services • Gives you one or more URLs for the service. • Go here to execute “echo”.

41. Echo Service WSDL, Section by Section

42. The WSDL Schema • See http://www.w3.org/TR/wsdl for the official recommendation. • The full WSDL schema is given here. • We focus on a specific example.

43. Front Matters <?xml version="1.0" encoding="UTF-8" ?> <wsdl:definitions targetNamespace="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:apachesoap="http://xml.apache.org/xml-soap" xmlns:impl="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" xmlns:intf="http://grids.ucs.indiana.edu:8045/GCWS/services/Echo" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">

44. Namespaces • The WSDL document begins with several XML namespace definitions. • Namespaces allow you to compose a single XML document from several XML schemas. • Namespaces allow you to identify which schema an XML tag comes from. • Avoids name conflicts. • As we will see, the Axis namespace generator went overboard. • Not all of these are used.

45. Namespace Quiz • What is the default namespace of our XML doc? • What does <wsdl:definitions …> mean? • What does xmlns:xsd=http://www.w3.org/2001/XMLSchema mean? • Is http://www.w3c.org/2001/XMLSchema a URI or a URL? • What is the target namespace of this document? • What is the target namespace used for?

46. Quiz Answers • http://schemas.xmlsoap.org/wsdl/ • This means <definitions> belongs to the schema named http://schemas.xmlsoap.org/wsdl/, labeled wsdl: in this doc. • It means that elements from the XML schema that appear in this WSDL document will be labled by <xsd:…> • Technically, it is used here as a URI; that is, it is a structured name. The URL does exist, however. • Recall URLs are special cases of URIs. URIs are names/identifiers. URLs also have a specific location on the web. • http://grids.ucs.indiana.edu:8045/GCWS/services/Echo • The target namespace is the namespace that will be used when we validate the document. • Note this isn’t used in our document since we define no complex types of our own. • See next section.

47. WSDL Types

48. WSDL Types • EchoService just has string messages. • So no special types definitions are needed in our WSDL. • Strings are an XML schema built-in type. • See earlier XML lectures.

49. Schema Built In Types

50. When Would I Need A Type? • Any time your Web Service needs to send data formatted by anything other than XML built-in types, you must define the type in WSDL. • Example: Arrays are not built-in types! • Arrays of strings, ints, etc., must be defined in the WSDL <type></type> structure.