Web Services

Agenda

  • Introduction
  • Web Services
  • SOA
  • API
  • Restcountries API - Code
  • Spotify API - Code
  • ToDo FastAPI App - Demo
Tue Hellstern

Why We Need Software Architecture

Architecture-less software becomes unmanageable with time and hence enhance the maintenance cost drastically with every new iteration.

As each and every change becomes costlier, this approach is termed as Big Ball of Mud

In your programs, have you thought about Software Architecture?

If Yes, in what way?

If No, is it something you missed?

Architectural approaches

Over the years of evolutions in software design, developers have come up with different architectural approaches in order to avoid the issues of architecture less software design - Big Ball of Mud.

The most famous ones.

  • Layered Architecture
  • Tiered Architecture
  • Service Oriented Architecture (SOA)

Layered Architecture

This approach works on principle of separation of concerns.

Software design is divided into layer laid over one another. Each layer performs a dedicated responsibility.

Architecture divides the software into the following layers

  • Presentation Layer
  • Business Logic Layer
  • Data Link Layer

Layered Architecture

Advantages

  • Simpler to implement
  • Abstraction due to separation of concerns among layers
  • Isolation between layers
  • More manageable due to low coupling

Disadvantage

  • Less scalability
  • Monolith structure, lacking ease of modifications
  • Data has to flow from each layer one after another
Oracle

Tiered Architecture

Divided the software into into tiers based on client server communication principle.

Can have one, two of n-tiered system separating the responsibilities among data provider and the consumer.

Single Tiered System

In this approach, single system is responsible to work as client as well as server and can offer ease of deployment eliminating the need of Inter System Communications (ISC).

This system are suitable only for small scale single user application and should not be used for multi user complex applications.

2-Tiered System

This system consist of two physical machines

  • server
  • client

It provides isolation among the data management operations and data processing and representation operations.

  • Client holds Presentation, Business Logic and Data link layer.
  • Server holds the Data stores such as Databases

3-Tiered / n-Tiered System

Highly scalable both horizontally and vertically. Implementing n-tiered architecture is generally costlier but offer high performance. Hence it is preferred in large complex software solutions.

It can be combined with advanced Service Oriented Architectural style to generate highly sophisticated model.

It is recommended to use this architecture when the software is complex and requires performance as well as scaling as it can be a costlier approach in terms of resources as well as time.

Difference between Layers and Tiers

Layer
Layers are the logical separation of code

  • Presentation Layer or UI Layer
  • Business Layer or Business Logic Layer
  • Data Access Layer and/or Data Layer

Tiers
Tiers are the physical deployment of layers

  • Presentation Tier - UI Tier
  • The Application Tier or Business Tier
  • The Data Access Tier
  • The Database Tier – SQL Server, MySQL

Web Services

Web Services

There a different definitions to Web Services - W3C is using:

A web service is a software system designed to support interoperable 
machine-to-machine interaction over a network. It has an interface described 
in a machine-processable format (specifically WSDL). 

Other systems interact with the web service in a manner prescribed by its description 
using SOAP-messages, typically conveyed using HTTP with an XML serialization in 
conjunction with other web-related standards.

For many, web services are synonymous with SOA (Services Oriented Architecture) and primarily rely on standards such as XML-RPC and SOAP (Simple Object Access Protocol).

Web Services Assignment

What are Web Services?

Find 3 uses of web services

Web Service example - Dollar Rent Car

The frontend or presentation layer can be in different programming languages and still have the ability to communicate with the Web Service.

What are Web Services?

  • Web Services include any software, application, or cloud technology that provides standardized web protocols (HTTP or HTTPS) to interoperate, communicate, and exchange data messaging
  • Applications can be written in various languages and are still able to communicate by exchanging data with one another via a web service between clients and servers.

Summarize - Web Service

  • Is available over the Internet or private (intranet) networks
  • Uses a standardized XML messaging system
  • Is not tied to any one operating system or programming language
  • Is self-describing via a common XML grammar
  • Is discoverable via a simple find mechanism

Components - Web Services

The basic web services platform is XML + HTTP

All the standard web services work using the following components:

  • SOAP
    Simple Object Access Protocol
  • UDDI
    Universal Description, Discovery and Integration
  • WSDL
    Web Services Description Language

How does a Web Service work?

A Web Service enables communication among various applications by using open standards such as HTML, XML, WSDL, and SOAP

  • XML to tag the data
  • SOAP to transfer a message
  • WSDL to describe the availability of service

You can use C# to build a new Web Services on Windows that can be invoked from your web application that is based on JavaServer Pages (JSP) and runs on Linux.

XML

Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable.

The World Wide Web Consortium's XML 1.0 Specification of 1998 and several other related specifications—all of them free open standards — define XML.

WSDL

  • WSDL stands for Web Services Description Language
  • WSDL is used to describe web services
  • WSDL is written in XML
  • WSDL is a W3C recommendation from 26. June 2007

SOAP

  • SOAP stands for Simple Object Access Protocol
  • SOAP is an application communication protocol
  • SOAP is a format for sending and receiving messages
  • SOAP is platform independent
  • SOAP is based on XML
  • SOAP is a W3C recommendation

REST - Representational State Transfer

In 2000 Roy Thomas Fielding defines REST (REpresentational State Transfer), which is the software architectural style of WWW.

It consist of a coordinated set of architectural constraints applied to components, connectors, and data elements, within a distributed hypermedia system.

Performance, Scalability, Simplicity, Modifiability, Visibility, Portability and Reliability

REST - Definition

REST is intended to evoke an image of how a well-designed Web application behaves:

a network of web pages (a virtual state-machine), where the user progresses through 
an application by selecting links (state transitions), resulting in the next page 
(representing the next state of the application) being transferred to the user 
and rendered for their use.

Roy Fielding in his Ph.D. dissertation in 2000

REST style

REST can be described as Set of formal and informal guides to creating architectures — constraints

  • Client-server
  • Stateless
  • Cacheable
  • Uniform interface
  • Layered system
  • Code on demand (optional)

REST vs. SOAP - 1

https://youtu.be/bPNfu0IZhoE

SOAP Python Demo

SOA

SOA - Service Oriented Architecture

SOA can be described as an approach to the development process, which, based on the business, leads to the development, acquisition and use of IT solutions as a set of business support, reusable and flexible services.

  • SOA organize contexts in a vertical way
  • Multiples components can be part of the same service providing multiples capabilities (operations)
  • An SOA service is like a bounded context
  • SOA fosters reuse and composition inside the same domain
  • Each SOA service represents a group of smaller components
  • In SOA, it is common to see all services using the same technology stack and the same database technology

API

What is an API?

Find the best, in your opinion, description of an API

Come up with some examples of API's

What is an API?

API stands for Application Programming Interface

But what is a Interface?

Interfaces

Every device you use has some kind of interface.

We use these interfaces to get the device to do the thing we want.

We don't need to understand the underlying functionality.

Abstraction

API's provide a layer of abstraction for the user.

Abstraction hides everything but what is relevant to the user, making it simple to use.

An API is how applications talk to each other

API - Application Programming Interface

API is a software intermediary that allows two applications to talk to each other.

You can ask an API for data, and they API will return what you want, usually in the form of JSON or XML. You can then use the data in your application.

Every time you use an app like Facebook, send an SMS, or check the weather on your phone, you’re using an API.

API's as a way to serve your customers

Some companies are packaging API's as products.

  • Weather Underground sells access to its weather data API

    • www.wunderground.com

  • e-conomic has an API where the customers can access there data

    • www.e-conomic.com

When a company offers an API to their customers, it just means that they’ve built a set of dedicated URLs that return pure data responses — meaning the responses won’t contain the kind of presentational overhead that you would expect in a graphical user interface like a website.

OpenAPI

There is the OpenAPI Specification (OAS), a technical specification that describes certain APIs, and there is the OpenAPI Initiative (OAI), an organization that enables specifications like OAS to thrive.

www.openapis.org

What is the difference between a Web service and an API?

An API is an interface that allows you to build on the data and functionality of another application, while a web service is a network-based resource that fulfills a specific task.

Yes, there's overlap between the two:

  • All web services are API's
  • Not all API's are web services
  • Web services require a network. APIs can be on- or offline, web services must use a network
  • Web services are usually associated with SOA
  • API's are protocol agnostic. API's can use any protocols or design styles - Web services use SOAP, REST, UDDI, XML-RPC

FastAPI

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.7+ based on standard Python type hints.

Flask <> FastAPI

When to use Flask?

  • To develop web applications
  • To develop quick prototypes

When to use FastAPI?

  • To develop APIs from scratch
  • To lower the number of bugs and errors in code

Microservices, SOA, and API's combined

API DEMO

API - restcountries

Spotify API

Spotify provides software and app developers access to some of their data about users, playlists, and artists through a Web API.

Newscatcher

IBM - SOA

SOA for Dummies

Links