webservice

Web Service

what

1. service available over web
2. enables communication between application over the web
3. provides a standard protocol/format for communication
4. platform indenpendent communition
5. using web services two different applications can talk to each other and exchange data/information

how

• Server (Service Provider)
  • a web service provider develops/implements the application(web service) and make it available over the internet(web)
• Client (Service Consumer)
• Client —-REQUEST—-> Server
• Client <—RESPONSE—- Server
• Menium:HTTP/INTERNET
• FORMAT:XML/JSON
• two web service implements:
  1. SOAP (Simple Object Access Protocol)
  • Medium:HTTP(POST)
  • Format:XML
  2. REST (RE:presentational State Transfer)
  • Menium:HTTP(POST,GET,PUT,DELETE…)
  • Format:XML/JSON/TEXT/YAML…

WSDL & UDDI

Consumer need to know:

• what are the services available？
• what are the request and response parameters?
• how to call the web service?

Service Provider publishes an interface for his web services that describes all arrtibutes o fthe web serives

This is XML based interface and is called - WSDL

• WSDL: Web Services Description Language

A web service provider publishes his web service through wsdl on an online directory from where consumers can query and search the web services. This online directory/registry is called UDDI

• UDDI: Universal Description,Discovery and Integration
• is an XML based standard for publishing and finding web services

SOAP Web Services

A web service that compiles to the soap web services specifications is a soap web services

1. who defines and dictates these standards?

• W3C (World Wide Web Consortium)

2. what are these specifications/standards?

• Basic
  • SOAP
  • WADL
  • UDDI
• Extended
  • WS - Security
  • WS - Policy
  • …
• SOAP: Simple Object Access Protocol
  • All information/message exchange happens over a common format:XML
  • XML messges have a defined structure:SOAP MESSAGE
  • SOAP MESSAGE consist of:Envelop (Header Body)

Rest Web Services

what is REST

• REpresentational State Transfer

A Resource’s Representation is transferred between server and client

a web servie that communications/exchanges information between 2 applications using REST architecture/principles is called a Restful Web Service

what are the principles/constrains od REST architecture?

1. Uniform Interface
   1. Resource: everything is a resource
   2. URI: any resource/data can be accessed by a URI
   3. HTTP: make explicit use of HTTP methods

• Using HTTP Methods along with URI, we can access/modify any resource or resource information

  Request	Response
  Get http://example.com/employees	list of employees
  Get http://example.com/employees/10	detail of employee with id=10
  Post http://example.com/employees +Data of new employee	id of new employee
  Delete http://example.com/employees/10	deletes employee with id=10
  Put http://example.com/employees/10 +Data to be changed	modifies data for emplyee 10

2. Stateless
   • all client-server communitions are stateless
   • improves Web Service Performance
3. Cacheable
   • happens at client side
4. Layered System
   • multiple layers can exist between client and server,e.g. Proxies Gateways
   • improves performance and scalability
5. Code On Demand(Optional)
   • ability to download and execute code on client side

Authorization 授权 & Authentication 认证

• Auhthorizatin: what can you do or what access do you have?
• Authentication: who you are?
• Why do we have Authorization and NOT Authentication in API Request?

How to create API documentation through WSDL url?

How to compare two wsdl?