Web Services

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Web Services

Index- Overview

- SOAP- WSDL- UDDI- Performance

basado en UPC-DAC/FIB-AAD Jordi Torres; v2.0-05/04

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Web Services

What are web services? - Web services are modular web applications that

provide data and services to other applications over the web

- Web services apply web technologies such as HTTP and XML to the concepts of distributed computing technologies such as CORBA and DCOM

- Aplicaciones auto-contenidas, auto-escritas que pueden ser publicadas, localizadas e invocadas a través de la Web

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Web Service Examples

A stock quote service. A weather service, a map service, a web

search service… - any composition of Web services.

e.g. Dollar Rent-A-Car- Create standard interfaces so business

partners could tap into the company's car reservation system.

Google, Amazon, …http://www.google.com/apis/

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What are Web Services? Today’s web:

- Web designed for application to human interactions• Information sharing: a distributed content library. • Built on very few standards: http + html• Shallow interaction model: very few assumptions

made about computing platforms.- Enabled B2C e-commerce.- Non-automated B2B interactions.

“Web services” is an effort to build a distributed computing platform for the Web.- Services available via the Web.- Meant mainly for application to application

communication (as opposed to users directly)Enables Business-to-Business transactions.

- E.g., a web service is contacted on a URL using the SOAP protocol over HTTP.

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Complete picture of distributed applications

(using WS)

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Core technologies used for WS

XML SOAP

- Simple Object Access Protocol - a framework for exchanging XML-based information in a

network - the currently most hyped XML/Web service technology

WSDL - Web Service Description Language - an XML-based language for describing network services - WSDL descriptions of capabilities and locations of services - like an interface description language for Web services - communication using SOAP or direct HTTP

UDDI - Universal Description, Discovery, and Integration- provides a registry mechanism for clients and servers to

find each other - uses SOAP for communication

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Otra definición

Programas accesibles en Internet que exponen su funcionalidad recibiendo/enviando mensajes SOAP a través de HTTP(s) y describen su interfaz en WSDL

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The Web Services Stack

ServicePublication/Discovery

ServicePublication/Discovery

ServiceDescription

ServiceDescription

XML MessagingXML Messaging

Transport NetworkTransport Network

UDDI

WSDL

SOAP

HTTP, SMTP, MQSeries, etc.

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What is SOAP?

SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment using XML.

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The Simple Object Access Protocol (SOAP)

XML-based protocol for messaging and

RPC

- Can works on top of existing transports

• HTTP, SMTP, FTP, MQSeries

Use of XML schema for encoding typed

values

Language independent

- Generation of SOAP messages available in

popular programming language

• C, Java, Perl

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SOAP: FORMATO GENERAL

Envelope

Body

HeaderHeader Key

Header Key

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SOAP: Formato general

SOAP especifica el formato de mensajes

Envelope: datos globales (codificación, espacio de nombres, ...)contiene: header (opcional) + body (obligatorio)

Body:contiene datos en formato XMLHeader: contiene meta-informaticón

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Sample HTTP Interaction

(C) Prof. Dr. Frank Leymann, IBM

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HTTP POST: Invoking Code

(C) Prof. Dr. Frank Leymann, IBM

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A Simple SOAP RPC( SOAP Message Embedded in HTTP Request)

POST /StockQuote HTTP/1.1Host: www.stockquoteserver.comContent-Type: text/xml; charset="utf-8"Content-Length: nnnnSOAPAction: "Some-URI"

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"> <SOAP-ENV:Body> <m:GetLastTradePrice xmlns:m="Some-URI"> <symbol>DIS</symbol> </m:GetLastTradePrice> </SOAP-ENV:Body></SOAP-ENV:Envelope>

Object Endpoint

Method nameInput parameter

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A simple soap response( SOAP Message Embedded in HTTP Response)

HTTP/1.1 200 OKContent-Type: text/xml; charset="utf-8"Content-Length: nnnn

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/> <SOAP-ENV:Body> <m:GetLastTradePriceResponse xmlns:m="Some-URI"> <Price>34.5</Price> </m:GetLastTradePriceResponse> </SOAP-ENV:Body></SOAP-ENV:Envelope>

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(three) standard aspects of SOAP

Overall message format A SOAP message is an envelope containing

zero or more headers and exactly one body.

The SOAP encoding rules defines a serialization mechanism that can be used to exchange instances of application-defined datatypes. ( based on XSD)

The SOAP RPC representation defines a convention that can be used (optional) to represent remote procedure calls and responses (if not, message-oriented style)

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Working example: A soap request

POST /servlet/rpcrouter HTTP/1.1

Host: www.messages.com

Content-Type: text/xml; charset="utf-8"

Content-Length: nnnn

SOAPAction: ""

<SOAP-ENV:Envelope

xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"

<SOAP-ENV:Body>

<ns1:getMessage xmlns:ns1="urn:NextMessage"

SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">

<UserID xsi:type="xsd:string">JDoe</UserID>

<Password xsi:type="xsd:string">0JDOE0</Password>

</ns1:getMessage>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

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Working example: soap response

HTTP/1.1 200 OK



<SOAP-ENV:Envelope>


<SOAP-ENV:Body>



<return xsi:type="xsd:string">Call mom!</return>

</ns1:getMessage>

</SOAP-ENV:Body>


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SOAP Endpoint Reference

POST /servlet/rpcrouter HTTP/1.1

Host: www.messages.com



SOAPAction: ""

<SOAP-ENV:Envelope


<SOAP-ENV:Body>



<UserID xsi:type="xsd:string">JDoe</UserID>

<Password xsi:type="xsd:string">0JDOE0</Password>

</ns1:getMessage>

</SOAP-ENV:Body>


85.34.235.95 80/servlet/rpcrouter/getMessage

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SOAP client-server interaction

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The Apache eXtensible Interaction System (AXIS)

A very flexible SOAP engine from Apache- Open and pluggable architecture

- Design to cope with various deployment configuration

• From very simplistic to highly sophisticated configurations

The Java Web Services facility (JWS)- Drop-in development

• Simplest and quickest way to deploy a Java-base Web Service

• Rename source file from xxx.java to xxx.jws

• Drop xxx.jws into JWS directory

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APIs de Java

SAAJ (SOAP with Attachment API for Java)tratar mensajes SOAP como objetos Java

JAX-RPC (Java API for XML based RPC)WSDL/XML <-> Java

API para cliente: WSDL, Invocación, proxy dinámico

JWSDLacceso a descripciones WSDL

JAXR (Java API for XML registries)acceso a registros de servicios Web

...

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Creación de un Servicio Web

Utilizar JWS- Con limitaciones (no package, ...)

WSDD (Web Service Deployment Descriptor)

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Creación de un cliente

1. Acceder a WSDLhttp: ....Calculator.jws?wsdl -> almacenar Calculator.wsdl

2. Generar stubsjava org.apache.axis.wsdl.WSDL2Java –p Calculator Calculator.wsdl

3. Clases generadas ls Calculator/ *.java

4. Compilar javac Calculator/ *.java

5. Compilar cliente javac ClienteCalculator.java

6. Ejecutar cliente java ClienteCalculator

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What is WSDL?

• WSDL describes network services by using an XML grammar.

• A WSDL document has a role similar to an IDL file in CORBA or the Remote Interface in a Java RMI implementation.

SOAP specifies the communication between a

requester and a provider

WSDL describes the services offered by the provider (an “endpoint”)

and might be used as a recipe to generate the proper SOAP messages to access the services.

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(using WS)

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WSDLservice

port

binding

port types

message

operation

types

1-M

1-1

1-1

1-M

1-M

1-M

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Types: xSchema definition of data

Port Types

Service

Port

Binding

Operations

Messages

Types

<types><schema

targetNamespace="http://example.com/stockquote.xsd"xmlns="http://www.w3.org/2000/10/XMLSchema"><element name="TradePriceRequest">

<complexType><element name="tickerSymbol" type="string"/>

</complexType></element><element name="TradePrice">

<complexType><element name="price" type="float"/>

</complexType></element>

</schema></types>

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Messages: meaningful collections of Types

Port Types

Service

Port

Binding

Operations

Messages

Types

<message name="GetLastTradePriceInput"><part name="body" element="xsd1:TradePriceRequest"/>

</message>

<message name="GetLastTradePriceOutput"><part name="body" element="xsd1:TradePrice"/>

</message>

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Operations: available Methods

Port Types

Service

Port

Binding

Operations

Messages

Types

<operation name="GetLastTradePrice"><soap:operation

soapAction="http://example.com/GetLastTradePrice"/><input>

<soap:body use="literal"/></input><output>

<soap:body use="literal"/></output>

</operation>

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Port Types: XML in/out for specific methods

Port Types

Service

Port

Binding

Operations

Messages

Types

<portType name="StockQuotePortType"><operation name="GetLastTradePrice">

<input message="tns:GetLastTradePriceInput"/><output message="tns:GetLastTradePriceOutput"/>

</operation></portType>

Maps Operations to Messages

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Binding: Maps Protocols to Methods (Http, etc.)

Port Types

Service

Port

Binding

Operations

Messages

Types

<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>

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Port: Maps URLs to Methods

Port Types

Service

Port

Binding

Operations

Messages

Types

<port name="StockQuotePort" binding="tns:StockQuoteBinding"><soap:address location="http://example.com/stockquote"/>

</port>

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Service: Packages ports & bindings

Port Types

Service

Port

Binding

Operations

Messages

Types

<service name="StockQuoteService"><documentation>My first service</documentation><port name="StockQuotePort"

binding="tns:StockQuoteBinding"><soap:address

location="http://example.com/stockquote"/></port>

</service>

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Document structure of WSDL

<definitions> element: the root of any WSDL - The name attribute specifies the name of

the Web Service (usually it corresponds to the file name).

- it contains a set of namespace definitions that are used throughout the document.

- ...

<definitions name ='weatherservice‘

xmlns='http://schemas.xmlsoap.org/wsdl/'>……

</definitions>

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<definitions> contains other elements- elements

• types• messages• portType• bindings• services• ...

- Each element within the document may contain a <documentation> element to provide some human readable explanation of the element that is specified.

- In addition, all the elements contain an attribute “name” serving as an identifier.

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Document structure of WSDL <types> element

- Provide data types definitions- All data type definitions relevant for sending

and receiving the messages described - The specification suggests using XML

schema definitions.

<types><schema

targetNamespace="http://add.fib.upc.es/symbol.xsd"xmlns="http://www.w3.org/2000/10/XMLSchema">

<element name="exampleType">...</element>...

</schema></types>

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<message> element- specifiy the data that will be communicated

between a requester and a service- may appear multiple times and consists of a

name and one or more <part> elements. - The parts specify the contents of the

message.<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>

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<operation> element- In order to tie the defined messages

together as a request-response pair corresponding to a method call.

- An operation specifies which message is the input and which message is the output.

<operation name='GetTemperature'>

<input message='wsdlns:Weather.GetTemperature' />

<output message='wsdlns:Weather.GetTemperatureResponse' />

</operation>

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<portType> element- The collection of all operations (i.e.

methods) exposed by your service

<portType name='WeatherSoapPort'> <operation name='GetTemperature'> <input message='wsdlns:Weather.GetTemperature' /> <output

message='wsdlns:Weather.GetTemperatureResponse' /> </operation>

 </portType>

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<binding> element- to bind the operation to the SOAP protocol.

The elements presented so far described our operation in a generic way (Nothing has been said about a concrete implementation).

- Next to a name attribute it contains a type attribute that references a portType and provides predefined binding for protocols such as SOAP, HTTP, and MIME.

<binding name='WeatherSoapBinding' type='wsdlns:WeatherSoapPort' >

…. </binding>

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<binding> element (cont)- Binding to SOAP

Inside the <binding> element you have a WSDL SOAP extension element called <soap:binding> which is used to specify the transport protocol you’re using (SOAP can be used over HTTP, SMTP, or possibly any other transport) and the style of request (rpc and document are the two styles).

<soap:binding style='rpc'

transport='http://schemas.xmlsoap.org/soap/http' />

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Document structure of WSDL <binding> element (cont)

• Then for each operation that this service exposes, you specify the value of the SOAPAction that is used for the HTTP header of SOAP message

<binding name='WeatherSoapBinding' type='wsdlns:WeatherSoapPort' > <soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/http' /> <operation name='GetTemperature' > <soap:operation soapAction='http://tempuri.org/action/Weather.GetTemperature'

/>....

</operation> </binding>

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Document structure of WSDL <binding> element (cont)

• There has to be at least one binding for every portType.

• In order to specify how the input and output messages of this operation are encoded, there is an operation element having three subelements: input, output, and fault. Each operation corresponds to an operation in the portType element.

<binding name='WeatherSoapBinding' type='wsdlns:WeatherSoapPort' > <soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/http' /> <operation name='GetTemperature' > <soap:operation soapAction='http://tempuri.org/action/Weather.GetTemperature' /> <input> <soap:body use='encoded' namespace='http://tempuri.org/message/'

encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/> </input> <output> <soap:body use='encoded' namespace='http://tempuri.org/message/'

encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/> </output> </operation> </binding>

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<service> and <port> element- A service is a set of related ports.

- The binding is specified within the port element.

- In order to bind to the SOAP protocol a <soap:address> is defined.

• It contains a name and a location that defines an address of the same type as the transport specified in the soap:binding element. That means that we have to define a HTTP address.

See the Web Service Example

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WSDL Structure Overview

portType- Abstract definition of

a service (set of operations)

Multiple bindings per portType:- How to access it

Ports- Where to access it

Service

Port(e.g. http://host/svc)

Binding(e.g. SOAP)

Abstract interface

portType

operation(s)

inMesage outMessage

Port

Binding

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WSDL Example:

float Weather::GetTemperature(String zipCode, bool celsius)

{

if (celsius)

return 21.7;

else

return 71.06;

}

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WSDL Example: Defining Services

You can think of the class as the Web service and the GetTemperature method as an operation on that service. To describe this service, you use the WSDL <service> element.

<definitions name ='weatherservice‘

xmlns='http://schemas.xmlsoap.org/wsdl/'> <service name='WeatherService' >

……</service>

</definitions>

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WSDL Example: Defining Services (cont.)

Each service is defined using a service element. Inside the service element, you specify the different ports on which this service is accessible.

The port definition would be like this:

<port name='WeatherSoapPort' binding='wsdlns:WeatherSoapBinding' >

<soap:address

location='http://localhost/demos/wsdl/devxpert/weatherservice.asp' />

</port>

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WSDL Example: Defining Services (cont.)

A Web service does not have to be exposed using SOAP. For example, if your Web service is exposed via HTTP GET, the port element would contain an <http:address/> element similar to this:

<http:address location="http://localhost/demos/wsdl/devxpert/weatherGET.asp"/>

A Web service may be accessible on many ports. For example, you might make your service available via SOAP and HTTP GET and possibly even via SMTP. For this Web service, you would have three ports each one with a different name.

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WSDL Example: What’s Your Message? (cont.)

To use Web services in a remote procedure call (RPC) model, there are two messages you must describe.

To describe the message structures, you use the WSDL <message> element. Each <message> contains zero or more <part> elements. A <part> corresponds to a parameter or a return value in the RPC call.

<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>

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WSDL Example: Port Types and Operations

An operation specifies which message is the input and which message is the output like this:

<operation name='GetTemperature'>

<input message='wsdlns:Weather.GetTemperature' />

<output message='wsdlns:Weather.GetTemperatureResponse' />

</operation>

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WSDL Example: Port Types and Operations (cont.)

The collection of all operations (i.e. methods) exposed by your service is called a portType and is defined using the WSDL <portType> element like this:

<portType name='WeatherSoapPort'> <operation name='GetTemperature'> <input message='wsdlns:Weather.GetTemperature' /> <output

message='wsdlns:Weather.GetTemperatureResponse' /> </operation>

 </portType>

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WSDL Example: Binding It All Together

We are now making a transition from abstract data types, messages, and operations to concrete physical representation of messages on the wire. To define the concrete aspects of operations, you use the WSDL <binding> element:

<binding name='WeatherSoapBinding' type='wsdlns:WeatherSoapPort' >

…. </binding>

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WSDL Example: Binding It All Together (cont.)

Inside the <binding> element you have a WSDL SOAP extension element called <soap:binding> which is used to specify the transport protocol you’re using (SOAP can be used over HTTP, SMTP, or possibly any other transport) and the style of request (rpc and document are the two styles). For example:

<soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/

http' />

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Then for each operation that this service exposes, we specify the value of the SOAPAction HTTP header :

<binding name='WeatherSoapBinding' type='wsdlns:WeatherSoapPort' > <soap:binding style='rpc'

transport='http://schemas.xmlsoap.org/soap/http' /> <operation name='GetTemperature' > <soap:operation

soapAction='http://tempuri.org/action/Weather.GetTemperature' />....

</operation> </binding>

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SOAP client-server interaction

(rep)

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Finally, we must specify how the input and output messages of this operation are encoded, the complete binding looks like this:

<binding name='WeatherSoapBinding' type='wsdlns:WeatherSoapPort' > <soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/http' /> <operation name='GetTemperature' > <soap:operation soapAction='http://tempuri.org/action/Weather.GetTemperature' /> <input> <soap:body use='encoded'

namespace='http://tempuri.org/message/' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/>

</input> <output> <soap:body use='encoded'

namespace='http://tempuri.org/message/' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/>

</output> </operation> </binding>

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What is UDDI?

Universal Description, Discovery, and Integration (UDDI) is a standard designed to provide a searchable directory of businesses and their Web Services.

Thus, it represents the service broker that enables service requesters to find a suitable service provider.

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(using WS)

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What is UDDI?

To get access to the UDDI services, the UDDI directory exposes a set of APIs in the form of a SOAP-based Web Service.

UDDI APIs - Publication API - Authenticated set of

operations that allow organizations to publish businesses, services, service type specifications

- Inquiry API - Non authenticated public set of operations that allows users to extract information out of the UDDI registry.

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What is UDDI?

UDDI classifies businesses and services according to standard taxonomies

Why Classification ?- Searches based on keywords alone, could return a

large set of hits for a particular search- Classification of services and businesses allows to

perform better searches

Registry Data• White Pages• Yellow Pages• Green Pages• ServiceType Registrations

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What is UDDI?(In many ways UDDI is designed like a phone book)

White Pages- contains business name, text description, contact info and other

related info.

- contains classification information about the business entity and

types of the services the entity offers. Searches can be performed to locate businesses which service a particular industry or product category, or that are located within a specific geographic region.

Green Pages- contains information about how to invoke the offered services.

• If a business entity were to offer its catalog online, its Green pages entry would have a reference to its catalog URL

Yellow Pages

Green Pages

White Pages

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Web Service Deployment

Remote UDDIWeb Service

Registry

Deploy ApplicationAs Service

ServiceProvider

WSDL FileGeneration and

Registration

WriteApplication

StartListener

WSDL

SOAP Request

1

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Dynamic Service Invocation

Remote UDDIWeb Service(Registry)

AutomaticService

Selection

Service Requestor

DynamicClient Code Generation

AutomatedWeb Service

Lookup

Web ServiceInvocation

SOAP Request

(SOAP Response)

SOAP Request

SOAP Response

1

Remote Web service

Publish Web Service

2

3

4

5

WSDL(s)

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Business registry nodes- http://uddi.microsoft.com- http://uddi.ibm.com- http://uddi.<companyname>.com- ...

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Web Services Performance

New technologies are often marketed with grand promises to solve business problems, but ... PERFORMANCE?

Performance criteria- simultaneous requests, - latency in responding to requests,- levels of operational degradation due to increases

in transaction loads.- ...

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Web service component stack

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Impact of parsing and marshalling

(source: http://www-106.ibm.com/developerworks/library/ws-best9)

Web Services

Documents

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