Web Services XML-RPC, SOAP, REST Advanced Web-based Systems | Misbhauddin

Advanced Web-based Systems | Misbhauddin

Web ServicesXML-RPC, SOAP, REST


PHP ScenarioWeb Server

HTTP Request

HTTP ResponseClient

exec w/environ

html

PHPCompiler

SQL

Database

SAME AS CGI

<?php $con = mysqli_connect($host, $user, $pwd, $db); $query = “SELECT name FROM user”; $result = mysqli_query($con,$query); $name = mysqli_fetch_array($result)[0];?><html><head><title>Test PHP Page</title></head><body> <h1>Welcome Mr. <?php echo $name; ?></h1>…….

Presentation+

Business Logic+

Data (SQL)=

All messed up


RIA Scenario

Web Server

XMLHTTP Request

XML Response

Browser

QUERY_STRING

XMLData

Server-Side Technology

SQL

Database

JavaScript

Update (HTML)

Presentation&

Visualization

BusinessLogic

Data &Models

Components of Data ExchangeTwo applications want to share data over the Internet• Initiating Action: Things don’t happen without any reason. A triggering

mechanism is needed.• Automatic: started at a fixed time (chron job, feed exchange)• User Initiated: form submission

• Data Format: Data needs to be stored and transferred in a format understood by both applications.

• Data Transfer Mechanism: Process to transfer the data over the internet


Data Transfer Mechanism• Selecting a proper protocol and data interchange format to pass data between

your app is one of the most important decisions to make during the development process• Common and widely used protocols• XML-RPC• SOAP• REST

• All of these protocols transport data over the HTTP protocol• XML-RPC & SOAP are XML-based• REST works both with JSON or XML



Web Services

• Web services are web application components• Unlike traditional client / server model (web server / web page system)• Does not provide user with a GUI• Share business logic, data and processes through a programmatic interface

across a network• The applications interface, not the users

Client / Server Web Services


Web Services

• Allow different applications from different sources to communicate with each other• Are not tied to any one operating system or programming language• Do not require the use of browsers or HTML• Web services are sometimes called application services


XML-RPC

• A set of implementations that allow software running on disparate operating systems, running in different environments to make procedure calls over the Internet• Remote procedure calling using HTTP as the transport and XML as the encoding

<methodCall> <methodName>sample.sumAndDifference</methodName> <params> <param><value><int>5</int></value></param> <param><value><int>3</int></value></param> </params></methodCall>


Simple Object Access Protocol (SOAP)• SOAP relies exclusively on XML to provide messaging services• The XML used to make requests and receive responses in SOAP can become

extremely complex• Technologies in SOAP

• WSDL - Web Services Description Language• UDDI - Universal Description, Discovery and Integration

SOAP


• Messaging protocol that allows programs that run on different operating systems

• Communicate using HTTP & XML

• Specifies how to encode HTTP Header and XML Data


WSDL

• It is written in XML• It is an XML document• It is used to describe Web services• It is also used to locate Web services

<definitions> <types> data type definitions........ </types>

<message> definition of the data being communicated.... </message>

<portType> set of operations...... </portType>

<binding> protocol and data format specification.... </binding></definitions>


WSDL<message name="getTermRequest"> <part name="term" type="xs:string"/></message>

<message name="getTermResponse"> <part name="value" type="xs:string"/></message>

<portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation></portType>

glossaryTerms is a function library, "getTerm" is a function with "getTermRequest" as the input parameter, and getTermResponse as the return parameter

UDDI• Is a directory service where businesses can register and search for Web services• Discover the right business from the millions currently online• Reaching new customers and increasing access to current customers• Solving customer-driven need to remove barriers • Describing services and business processes programmatically in a single, open,

and secure environment


Saudi Airlines

Fly Dubai

Ticket Rate

Register

Register

Travel AgenciesFind Airline Interface

UDDI

SOAP Building Blocks• A SOAP message is an ordinary XML document containing the following elements:• An Envelope element that identifies the XML document as a SOAP message• A Header element that contains header information• A Body element that contains call and response information• A Fault element containing errors and status information


<?xml version="1.0"?><soap:Envelope xmlns: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>

SOAP Envelope Element• It is a required element• It is the root element of a SOAP message• It defines the XML document as a SOAP message


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

</soap:Envelope>

Namespace• Defines the Envelope as a

SOAP Envelope• Same as <!DOCTYPE html>

Encoding Style• Defines the data types

used in the document• Included as a URI

SOAP Envelope Element• It is a required element• It is the root element of a SOAP message• It defines the XML document as a SOAP message


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

</soap:Envelope>

Namespace• Defines the Envelope as a

SOAP Envelope• Same as <!DOCTYPE html>

Encoding Style• Defines the data types

used in the document• Included as a URI

SOAP Body Element• Contains the actual SOAP message


<soap:Body> <m:GetPrice xmlns:m="http://www.panda.com/prices"> <m:Item>Apples</m:Item> </m:GetPrice></soap:Body>

<soap:Body> <m:GetPriceResponse xmlns:m="http://www.panda.com/prices"> <m:Price>1.90</m:Price> </m:GetPriceResponse></soap:Body>

Request

Response


<message name="getPriceRequest"> <part name="Item" type="xs:string"/></message><message name="getPriceResponse"> <part name="Price" type="xs:double"/></message><portType name="glossaryPrice"> <operation name="getPrice"> <input message="getPriceRequest"/> <output message="getPriceResponse"/> </operation></portType> <binding type="glossaryTerms" name="b1"> <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" /> <operation> <soap:operation soapAction="http://example.com/getPrice"/> <input><soap:body use="literal"/></input> <output><soap:body use="literal"/></output> </operation></binding>


SOAP

Advantages• Platform and language

independent• Simplified communication

through proxies and firewalls• Work with different transport

protocols – HTTP, SMTP ….

Disadvantages• Slower than other protocols• Uses verbose XML• Not used for event notifications• Firewall latency• Different level of support based

on the programming language (PHP, JAVA, Python, .Net)

REST


• Representation State Transfer• Set of architectural principles – data transmitted over

HTTP• Focus on design rules for stateless service• Each resource is represented using a unique URI• Representation of the resource is returned• With each representation, client can transfer state

REST


• RESTful web services are completely stateless• Good caching infrastructure over the HTTP GET method• Well used for restricted profile devices such as mobile and PDA

(SOAP has more headers and not very useful)• Simpler than SOAP

URLS


• Identify the things that you want to operate on – meaning RESOURCES

• A web page is a type of resource

/professors List of all professors at CCSIT

/professors/Misbhauddin Identify professor named ‘Misbhauddin’

GET /professors/Misbhauddin HTTP/1.1 Host: kfu.edu.sa/ccsit

Resources are best thought of as nouns

Actions


• Lets say we want to add a new professor

Use a specific URL OR ……

Two ways

/professors/addUse HTTP Verbs

GET /professors/Misbhauddin HTTP/1.1 Host: kfu.edu.sa/ccsit

Not RESTful

HTTP Verbs


• HTTP verbs tell the server what to do with the data identified by the URL.

GET instructs the server to transmit the data identified by the URL to the client

PUT used when you wish to create or update the resource identified by the URL

DELETE used when you want to delete the resource identified by the URL of the request

POST used when the processing happen on the server

Representations


• The HTTP client and HTTP server exchange information about resources identified by URLs

• Typically resource is represented using JSON or XML• Example• Resource: person (Mohammed)• Service: contact information (GET)• Representation:• Name, address, phone number• JSON or XML format

REST Constraints


• The six constraints are:• Uniform Interface• Stateless• Cacheable• Client-Server• Layered System• Code on Demand (optional)

Uniform Interface | REST


• Defines the interface between the client and the server• Simplifies and decouples the architecture• Identification of resources; • Manipulation of resources through representations;• Self-descriptive messages;

• Fundamental to RESTful Design• HTTP Verbs: (GET, PUT, POST, DELETE)• URI (Resource Name)• HTTP Response (status, body)

Stateless| REST


• Server contains no client state• Each request contains enough context to process the

message• Self-descriptive messages;

• Any session state is kept on the client

Client-Server| REST


• Assume a disconnected system• Separation of Concern• Uniform Interface is the link between the two

Cacheable| REST


• Server responses (representations) are cacheable• Implicitly• Explicitly• Negotiated

Layered System| REST


• Client cannot assume direct connection to the server• Software or hardware intermediaries between the server

and the client• Improves scalability

Code on Demand| REST


• Server can temporarily extend the client• Transfer logic to client• Client executes logic• For example• JavaScript• Applets

• Optional


SOAP vs. REST

SOAP• Language, platform, and transport

independent (REST requires use of HTTP)• Works well in distributed enterprise

environments (REST assumes direct point-to-point communication)

• Standardized• Provides significant pre-build extensibility

in the form of the WS* standards• Built-in error handling• Automation when used with certain

language products

REST• No expensive tools require to interact

with the Web service• Smaller learning curve• Efficient (SOAP uses XML for all

messages, REST can use smaller message formats)• Fast (no extensive processing

required)• Closer to other Web technologies in

design philosophy


Recommended Reading

For the REST architecture

http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm

Documents

Web Services XML-RPC, SOAP, REST Advanced Web-based Systems | Misbhauddin