What are Web Services? Definition of web service A web service is a distributed unit of business logic that can be accessed over Internet standard web.

What are Web Services?

Definition of web service A web service is a distributed unit

of business logic that can be accessed over Internet standard web protocols, such as HTTP and that uses XML for sending and receiving messages.

Client Web Service Business Logic

Network Call

Goals of Web Services

To solve interoperability in a platform-neutral way and remove all that mismatches that exist between the various vendors.

To create an abstraction layer between heterogeneous nodes on the network.

To be highly accessible to all platforms through the use of Internets protocols and XML.

To enable interoperability between any type of system.

To provide a solution to bypass firewalls, thus allowing any client to access a remote services.

To take advantage of reduction in communication and server costs.

To advocate designing software as a set of distributed services rather that a component run within a singles process.

Web pages Vs Web servicesCharacteristics Web pages Web services

Transport mechanism

HTTP, SMTP, FTP HTTP, SMTP, FTP

URLs Yes Yes

Message Format HTML XML

Information Type Embedded Data Structured Data

Interactive Yes (DHTML) No

Remote application Communication

No Yes

Platform Neutral Yes Yes

Deployed environment

Web/Application server

Web/Application server

Distributed Model Client/Server P2P

Web service Technology Stack

Discovery

Description

Messaging

Transport

Network

UDDI, DISCO, WSIL, ebXML

WSDL, RDF, ebXML

SOAP, XML-RPC (XML)

HTTP, SMTP, FTP

TCP/IP, UDP

Layer Protocol/ Standard

UDDI : Universal Description Discovery and IntegrationDISCO : Web Service Discovery Tool WSIL : Web Services Inspection LanguageRDF : Resource Description FrameworkUDP : User Datagram Protocol

Web services Architecture

Provider The provider is essentially the company offering a set of

Web Services. Consumer The consumer in P2P model is essentially a client that

can do 2 things; discover and consume set of web services.

Registry This is essentially an XML base repository for business

entities and list of published services offered by organizations.

Consumer Registry

Provider

1. publish

2. Discover

3. Bind

Web Service Development Life-Cycle

Design

Implementing &Test

Describe

Deploy

Publish

Maintain

Web Service Development Life-Cycle

Design Figure out what kind of Web Services want to build. Whether

legacy business logic is to be expose or new code should be created or several existing web services should be aggregated to coordinate a business process etc. Decide what kind of tool kits to use and which protocols should be used.

Implementing and Test Create a Web Service server using selected tool kit. Test

interoperability issues between the various toolkits, ex : both PHP and other platforms.

Describe and Deploy Create a description document using WSDL and deploy the

service on server. Publish (Optional) Optionally, your organization may wish to publish your web

service to a UDDI registry. Maintain Ensuring the application is performing, is secure, and that

the developers may implement new features and bug fixes as required.

HTTP

Hyper Text Transfer ProtocolHTTP 1.0HTTP 1.1The default mechanism of

communication for the World Wide Web.

HTTP 1.0 Header

Request Header GET /index.php HTTP/1.0Response Header HTTP/1.0 200 OK Date : Fri, 09 August 2008 11:53:56

GMT Content Length : 152 Content-Type : text/html

HTTP 1.1 Header

Request Header GET /index.php HTTP/1.1 Accept : image/gif, image/jpeg, */* Accept-Language : en-us Accept-Encoding : gzip, deflate User-Agent : Mozilla/4.0 (compatible; MSIE

6.02; windows NT) Host : www.domain.com:80 Connection : Keep-Alive

HTTP 1.1 Header

Response Header HTTP/1.1 200 OK Date : Fri, 09 August 2008 11:53:56 GMT Server : Apache X-Powered-By: PHP/4.4.9 Last-Modified : Thu, 08 August 2008 11:53:56

GMT Content Length : 152 Connection : close Transfer-Encoding : chunked Content-Type : text/html

HTTP methods

Get Post Head The client sends a HEAD request when it wants to see only

the headers of a response, such as Content-Type or Content-Length.

Put Allows a client to place a file on the server and is similar to

sending a file by FTP. Delete The DELETE operation allows a client to remove a

document or Web page from the server. Options The OPTIONS request determines which HTTP methods

the server supports and returns an appropriate header. Trace A TRACE returns the headers sent with the TRACE request

to the client, so that they can be used in debugging.

HTTPS

HTTPS (HTTP over SSL or HTTP Secure) is the use of Secure Socket Layer (SSL) or Transport Layer Security (TLS) as a sub layer under regular HTTP application layering.

HTTPS encrypts and decrypts user page requests as well as the pages that are returned by the Web server.

The use of HTTPS protects against man-in-the-middle attacks.

HTTPS was developed by Netscape.

XML-RPC Overview

XML-RPC Client XML-RPC Server

Web Browser

HTTP

Client make request to the server and fetches request

Browse interacts with HTML based application

Client make request to the server and fetches request

Server receives request and renders response

for client to fetch

•XML-RPC is a remote procedure call protocol encoded in XML•First web service protocol•Use HTTP POST method

XML-RPC Request

POST /web_service_api/xmlrpc_server.php HTTP/1.1User-Agent: PHP/xmlrpc_clientHost: www.domain.comContent-Type: text/xmlContent-Length: 189Connection: Close

<?xml version="1.0" encoding="iso-8859-1"?><methodCall><methodName>hello</methodName><params> <param> <value> <string>XML-RPC</string> </value> </param></params></methodCall>

XML-RPC Request Header

The first linePOST /web_service_api/xmlrpc_server.php HTTP/1.1

The general format is [method][responder][protocol]

The method used here is HTTP POSTThe responder defines how the remote

device should handle the request. Where PHP is concerned, this will be the location and name of the XML-RPC server script

In the protocol field, defined the version of the HTTP using (HTTP 1.0 or HTTP 1.1)

XML-RPC Request Header (Cont)

On the second line User-Agent: PHP/xmlrpc_client

The user agent as a string that identifies the XML-RPC client

Third line Host: www.domain.com

This is used to identify the server to which the request is being sent.

Optionally we can specify a port number hereHost: www.domain.com:8080

XML-RPC Request Header (Cont)

Combining the first and third lines, we have the complete path to our server:www.domain.com/web_service_api/

xmlrpc_server.php On the line four and five, defines the

Content-type, text/xml, and the length of the data being sent to tell the server how much data to except.

XML-RPC Request Header (Cont)

Finally we have the header: Connection: Close

HTTP 1.1 allows for the possibility of the HTTP connection remain open, so we can submit further request. However, a PHP script expecting an FEOF will be waiting indefinitely for the response to finish.

The Payload

The payload contained within a single XML structure: <methodCall>. In side the method call, the method name want to use

along with any associated parameters.<?xml version="1.0" encoding="iso-8859-1"?><methodCall>

<methodName>hello</methodName><params> <param> <value> <string>XML-RPC</string> </value> </param></params>

</methodCall>

XML-RPC ResponseHTTP/1.1 200 OKConnection: Close Content-Length: 189Content-Type: text/xmlDate: Wed, 12 Feb 2006 13:43:03 GTMServer: domain.com/PHP_XMLRPC_SERVER

<?xml version="1.0"?><methodResponse><params> <param> <value> <string>Hello XML-RPC</string> </value> </param></params></methodCall>

XML-RPC data types - Scalars

Data Type XML Tag Example Values

Four-byte signed integer

<i4> or <int> -234, 1435

Boolean <boolean> 0(false) or 1(true)

ASCII String <string> Hello World!

Double precision floating point

<double> -43.342

ISO 8601 Format Date

<dateTime.iso8601>

20060212T12:00:00

Base64-encoded binary

<base64> eW3434DSgDG#$

XML-RPC data types - Arrays

An array are all ways contains a single <data> element, which it self can contains multiple values of any type.<params>

<param> <value>

<array> <data>

<value><double>1.4</double></value> <value><double>3.4</double></value>

</data> </array>

</value> </param>

</params>

XML-RPC data types - Struts Which allow us to constructs similar to an associative array

of named keys and element in PHP.<params> <param> <value> <struct> <member> <name>name</name> <value> <string>John</string> </value> </member> <member> <name>age</name> <value><int>23</int></value> </member> </struct> </value> </param></params>

XML-RPC Fault Response

<?xml version="1.0"?><methodResponse> <fault> <value> <struct> <member> <name>faultCode</name> <value><int>4</int></value> </member> <member> <name>faultString</name> <value><string>Too many parameters.</string></value> </member> </struct> </value> </fault> </methodResponse>

• Contains fault code and fault string to identify the errors.• No global list if error messages.• Its up to the developer to assign the fault codes and corresponding fault strings

XML-RPC Introspection Methods

system.listMethods() – Lists currently registered methods

system.describeMethods() – Describes the available methods in detail

system.methodHelp() – Return documentation for a specified methid

systen.methodSignature() – Returns signature for a specific method

system.getCapabilities() – Lists server capabilities

What is SOAP?

SOAP stands for Simple Object Access Protocol SOAP is a communication protocol SOAP is for communication between

applications SOAP is a format for sending messages SOAP communicates via Internet SOAP is platform independent SOAP is language independent SOAP is based on XML SOAP is simple and extensible SOAP allows you to get around firewalls SOAP is a W3C recommendation

SOAP vs XML-RPC

Everything that XML-RPC can do, SOAP does as well.

XML-RPC is much simpler SOAP makes it easier to exchange more

complex documents. SOAP runs over many protocols: HTTP, SMTP, FTP, … SOAP allows developers to create their

own types using XML schemas.

SOAP Message Skelton

<?xml version="1.0"?><soap:Envelopexmlns:soap="http://www.w3.org/2001/12/soap-envelope"soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">

<soap:Header>...</soap:Header>

<soap:Body>... <soap:Fault> ... </soap:Fault></soap:Body>

</soap:Envelope>