T110 5140 Network Application Frameworks and XML Web

T-110. 5140 Network Application Frameworks and XML Web Services and WSDL 02. 04. 2007 Sasu Tarkoma Based on slides by Pekka Nikander

What is WSDL? n n WSDL: Web Service Description Language An XML language used to describe and locate web services u u u n n Commonly used to describe SOAP-based services W 3 C standard (work in progress) u u u n location of web service methods that are available data type information and XML messages Initial input: WSDL 1. 1 as W 3 C Note Current version 2. 0 (Candidate Recommendation) Some differences between 1. 1 and 2. 0 WSDL 1. 1 in WS-I Basic Profile 1. 0 and 1. 1.

WSDL Document Elements (v. 1. 1. ) n n n <types> - data type definitions <message> - Abstract definition of the data being transmitted <port. Type> - A set of abstract operations <binding> - Concrete protocol and data format specifications for the operations and messages defined by a particular port. Type. Endpoint type. <port> - An address for binding. Endpoint instance. <service> - A set of ports.

WSDL Overview <definitions>: ROOT WSDL element <types>: The data types that are used <message>: What messages are transmitted? <port. Type>: The supported operations <binding>: The binding to concrete protocols <service>: Reference to actual location

A WSDL Document n n A WSDL document contains two parts Abstract part u n Concrete part u n Interfaces, types, messages Binding to conrete protocol and encoding May be published separately u u Interfaces agreed between many companies Each company published their own implementation in UDDI and import the abstract interface.

Mapping SOAP to WSDL 6

Message Styles n n n The WSDL 1. 1 specification defines two SOAP message styles Determined in binding Document u u u n <soap: Body> contains one or more child elements called parts There are no SOAP formatting rules for what the <soap: Body> contains preferred, loose coupling, easy validation RPC u u u <soap: Body> contains an element with the name of the method or remote procedure being invoked This element in turn contains an element for each parameter of the procedure less popular today, tighter coupling

The main structure (v. 1. 1) <definitions namespace = "http: //. . "> <types>XML Schema types</types> <message>. . </message> <port. Type>a set of operations</port. Type> <binding>Communication protocols</binding> <service>A list of binding and ports</service> </definitions>

Types n n <types> define data types used in message declaration For platform neutrality, WSDL uses XML Schema syntax to define data u u XML Schema must be supported by any vendor of WSDL conformant products Other kinds of type definitions also possible F u Possible interoperability issues If the service uses only XML Schema built-in simple types, such as strings and integers, the types element is not required

WSDL Messages n The <message> element defines the data elements of an operation u u n n n the name of the message contains zero or more message part elements The parts can be compared to the parameters of a function call in a traditional programming language All parts are typed by an XML Schema type V. 2. 0 changes: message element is not used, replaced by patterns

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

Operation Types (v. 1. 1) n n n 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 endpoint sends an output message and then receives an input message. Notification: The operation can send a message but will not wait for a response v. 2. 0 changes: abstract message patterns

Example <port. Type name="Stock. Quote. Port. Type"> <operation name="Get. Last. Trade. Price"> <input message="tns: Get. Last. Trade. Price. Input"/> <output message="tns: Get. Last. Trade. Price. Output"/> </operation> </port. Type>

One way and Notification Example <port. Type name="Register. Port"> <operation name="register"> <input name="customer. Info" message="Reg. Info"/> </operation> <operation name="register. Response"> <output name="response" message="Response. Info"/> </operation> </port. Type>

Putting it together Source: http: //msdn. microsoft. com/

WSDL 2. 0 n n 3 specifications Part 1: Core u n Part 2: Message Exchange Patterns u n Predefined types of interactions Part 3: Bindings u n Abstract interfaces, independent of protocol and encoding SOAP and HTTP/MIME binding Lot’s of changes from 1. 1

Changes from 1. 1 to 2. 0 n n Adding further semantics to the description language. Removal of message constructs. These are specified using the XML schema type system in the types element. No support for operator overloading. Port. Types renamed to interfaces. Support for interface inheritance is achieved by using the extends attribute in the interface element. n Ports renamed to endpoints. n Abstracted message patterns

WSDL 2. 0 Conceptual Model Source: http: //webservices. xml. com/pub/a/ws/2004/05/19/wsdl 2. html

Message Exchange Patterns MEP Description Fault in-only Single input message No robust-in-only Single input message Trigger In-out Input message + output message Replace out-only Single output message No robust-only-out Single output message Trigger out-in Output followed by input msg Replace out-optional-in Output followed by an opt. Input Trigger in-optional-out Input followed by an opt. Output Trigger

Implementations n Microsoft. NET u n Java API for XML-based RPC (JAX-RPC) u n n SOAP 1. 1, WSDL 1. 1 Java API for XML Registries (JAXR) Apache Axis u u u n SOAP 1. 1, WSDL 1. 1 Tools for automatically creating WSDL to/from Java SOAP 1. 1 and 1. 2, WSDL 1. 1, JAX-RPC 1. 0 Axis 2 supports WSDL 2. 0 component model IBM Websphere, BEA Web Logic, SAP Net. Weaver, …

Uses of WSDL documents n Description of service interfaces u Compile-time F u Run-time F n Developer uses WSDL before service deployment Client downloads WSDL description and uses the info it provides to execute the service As a side-effect u u u Developers can use WSDL to speed up the development of code WSDL Java code Java interfaces WSDL

Summary n n Deferred binding, using Web, composition Some details and conventions still unclear u n Possible interoperability issues Parts hard to understand u u Namespaces Schemas Differences between versions Document vs. RPC SOAP style F F Also literal vs. encoded More about this next week