INFOSYS 290, Section 3, Fall 2005, Web Services: Concepts, Design and Implementation Adam Blum Lecture 2: Describe and Invoke - SOAP and WSDL

Today’s Content SOAP Comparison with other distributed technologies –Corba –DCOM –Java RMI WSDL Web services survey –SalesForce sforce –Siebel –Xmethods examples

Service Broker Basic SOAP Message Exchange Service Consumer Service Provider http transport SOAP message WSDL describing service SOAP message http transport client service registry find publish DESCRIBE INVOKE SOAP SenderSOAP Receiver SOAP Sender SOAP Receiver

SOAP Body SOAP Message SOAP header SOAP envelope Header block Header data Header data Header data Body child element

Sample SOAP Message T14:00:00-05:00 Pick up Mary at school at 2pm

Conversational Message Exchange buyer seller message broker RFQ QuoteResponse Award

Conversational SOAP Message Exchange: A Request – – – SanDisk – SecureDigital memory – 1GB – – 100 –

Conversational Exchange: A Response – env:mustUnderstand=“true”> – – KingMax – SecureDigital memory – 1GB – 9000KB/s – Memories Unlimited – KM-SD1000 – 100 –

Conversational Exchange: Completion – – – KM-SD1000 – 50 –

Remote Procedure Calls To invoke RPC –Address of target SOAP node –Method name –Identities and values of arguments –Separation of arguments identifying target of RPC versus data Plus values of properties for binding (e.g. GET, POST) –Optional header data

RPC Invocation g

RPC Result 5 <s:shipOrderResponse env:encodingStyle=“ encoding” encoding xmlns:rpc=“ xmlns:s=“ s:status confirmed $20.00

SOAP Faults Place faults inside env:Body elements In single env:Fault env:Node identifies node which generated fault –Absence indicates “ultimate recipient” env:Code –env:Value –env:Subcode env:Reason –env:Text env:Detail –Application specific

SOAP Fault Example – – env:Sender – » rpc:BadArguments – – Processing error – Chyba zpracování – Unknown destination 999 – –

SOAP Faults on MustUnderstand env:MustUnderstand Header not understood En-tête non compris

SOAP Processing Model SOAP messages are sent from one sender node passing through zero or more intermediaries Three roles –next: each SOAP intermediary or end destination must act in this role –none: SOAP nodes must not act in this role –ultimateReceiver: destination acts in this role Header blocks targeted to specific roles using Role attribute If mustUnderstand=“true” SOAP receiver must understand or generate SOAP fault Header blocks processed by intermediaries are generally removed before forwarding –Override with relay attribute –Allows targeting of headers to specific intermediaries (but mustUnderstand would then generally be turned off)

SOAP Extensibility in Practice – dhw6weiurU982ndya73jdVBGt d79HID7ghd652ad2 – 10 –...

SOAP Processing: Header Blocks, MustUnderstand and Relay – – –......

SOAP Bindings specify how SOAP messages may be passed from one SOAP node to another using an underlying protocol provides a serialized representation of the message provides a mechanism to support features needed by SOAP applications (security, reliability, etc...) describes the features it provides

SOAP HTTP Binding Example POST /Reservations HTTP/1.1 Host: marketplace.example.org Content-Type: application/soap+xml; charset="utf-8" Content-Length: nnnn –

SOAP SMTP Binding Example From: To: Subject: RFQ: Memory purchase Date: Thursday, September Message-Id: Content-Type: application/soap+xml

SOAP Remoting Architecture Server object implementation application level Client application code Server skeleton XML unmarshaller Client stub XML marshaller TCP/IP socket remoting architecture level wire protocol level http protocol http server http server body envelope header

So What’s Different? Open format usable from any platform Easy to understand and debug Stable supported interfaces Standards enable “expose service once” and have multiple consumers –versus typical point to point integration efforts Easy for intermediaries to process messages and add value –Routing and delivery –security –management and monitoring –schema and service design – acceleration Easy to extend with additional semantics

CORBA Server object implementation application level Client application code Server skeleton Corba runtime Implementation repository Client stub Corba runtime Implementation repository ORB TCP/IP socket

CORBA Dynamic Invocation Server object implementation application level Client application code Server skeleton Corba runtime Implementation repository Client stub Corba runtime Implementation repository ORB TCP/IP socket binding method Remoting architecture level Wire protocol level

CORBA Scalability –Stateful programming model - –Shared activation + Performance –CORBA is only intermediary until object obtained (allowing direct client-server interaction) + –Binary transport + Activation –Sophisticated four policy activation methods + State Management –Provides state management with a connection-oriented protocol + Garbage Collection –Implemented on per ORB vendor basis –No concept of distributed memory management Security –Just uses SSL -

DCOM and DCE RPC Server object implementation application level Client application- code Server stub COM runtime Client proxy COM runtime SCM RPC channel binding method Remoting architecture level Wire protocol level registry OXID Resolver Ping client/server

DCOM Object Creation Server object implementation application level Client application- code Server stub COM runtime Client proxy COM runtime SCM RPC channel binding method Remoting architecture level Wire protocol level registry OXID Resolver Ping client/server

DCOM Object Invocation Server object implementation application level Client application- code Server stub COM runtime Client proxy COM runtime SCM RPC channel binding method Remoting architecture level Wire protocol level registry OXID Resolver Ping client/server

DCOM Comparison Scalability –Not scalable due to garbage collection and connection overhead –All clients involved in call required to send pings to servers at two minute intervals Performance –Many roundtrips to activate and use remote object Activation –Client obtains reference to remote object’s class object through local SCM from remote SCM –Client creates instances of remote objects through its proxy State Management –DCOM goal: location transparency –Makes it very difficult to have a stateless model User interface IFaces Iteration IFaces Garbage Collection –After three ping fails, server cleans up resources for objects owned by remote client Security –Provides authentication, authorization and identity –Many authentication methods

Java RMI Server object implementation application level Client application- code Server skeleton Remote Reference Layer Client stub Remote Reference Layer Transport Layer binding method remoting architecture level wire protocol level Transport Layer TCP/IP Socket RMI Registry

JRMP signature (JRMI) version protocol SingleOpProtocol StreamProtocol MultiplexProtocol Message (serialized arguments based On Java’s Object Serialization Protocol)

RMI Comparison Scalabilitiy –Good overall –Registry could be bottleneck Performance –Fairly high –Use from Java applets in browser cause conversion to http –expensive Activation –Stub can be download over the network –Lazy activation and selection of specific server instances –Allows automatic instantiation of objects based on methods faulting and the fault resolution process instantiating the remote object State Management –Provides both connection-oriented and connectionless protocols (good!) Garbage Collection –Distributed reference counting (like CORBA, DCOM) –Reference to remote objects is considered lease on object, which must be periodically renewed Security –Strong security –Must have security credentials to perform dynamic class loading

SOAP Comparison Scalability –Very scaleable especially over http if request/response model is maintained Performance –Degraded by XML overhead –But if you’re interoping between architectures anyway that overhead isn’t unreasonable Activation –Beyond SOAP’s scope State Management –Stateless if over http Garbage Collection –Beyond scope Security –https/SSL - not ideal for routability of course –WS-Security Other Disadvantages –No true standard serialization method –Multiple copies of objects transported Other Advantages –Encouragement of loose coupling (both physical and interface) –Protection of apps from changes in standards –Truly vendor-agnostic

Web Services Description Language Provides a model and an XML format for the “contract” of a web service Separates abstract service description from both concrete network protocol and message format Describes data types used in messages Messages are defined as aggregation of typed parts Operations are message exchange patterns supported by the web service PortTypes are named collections of operations

WSDL Components Types– a container for data type definitions using some type system (such as XSD). Message– an abstract, typed definition of the data being communicated. Operation– an abstract description of an action supported by the service. Port Type–an abstract set of operations supported by one or more endpoints. Binding– a concrete protocol and data format specification for a particular port type Port– a single endpoint defined as a combination of a binding and a network address. Service– a collection of related endpoints.

WSDL Specification types message operation porttype operation binding service port

An Example - WSDL Types

WSDL Operations

WSDL Bindings, Services, Ports My first service

Import for Types

WSDL Binding maps the abstract service functionality to a specific network protocol and message format defines: –the communication protocol to use –how service interactions are accomplished using this protocol –the address to communicate with Three bindings are defined in the WSDL spec: –SOAP binding – HTTP binding – SMTP binding

WSDL Binding Example: One-way Over SMTP – – – – – –

Request-Response RPC Over HTTP – – – > My first service

Web Services Client Tools –MindReef –AboveAll

Web Services Survey XMethods examples –Focus on “informational web services” Business APIs –SalesForce –Siebel CRM OnDemand –PayPal

Course Project Goal –Build “web service consuming” client applications from desktops and mobile devices Requirements –Use an “informational” web service Has QCUD (Query, Create, Update and Delete operations) –Consume web service from AboveAll or Visual Studio for desktop –Consume WS from GoodAccess Web Services or Visual Studio from mobile device –Optionally write or enhance a backend web service Possibly as a “proxy web service” layer on top of original web service Only if previous steps are achieved –Demo to class –Write up as three page paper including: architecture and UI design Team size –Two people per project Proposal –Due next week: September 8, 2005

References Specs –SOAP Specification, –WSDL Specification, –UDDI Specification, Tools –Visual Studio, –Microsoft Web Services Enhancements

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