Service-Oriented Software

Michael Godwin Ben Miller

Neil Wilson Lingiie Ye

Introduction

•  Background of Service-Oriented Software

•  Service-Oriented Architecture (SOA)

• Where SOA is used

•  How you can create your own service

What is SOA? •  The future!! (arguably)

• Mash-up of multiple services in one site

•  Services are autonomous

•  Usually used in web-based software

•  Designed to meet users ever-changing needs

Advantages •  Simplifies understanding the software

•  Allows for simplified modifications •  Adding/removing services is easy •  Debugging services is easy

•  Centralized data

•  Versatility

•  High fault tolerance

Disadvantages

• Not suited for applications that require a lot of data transfer

•  Requires complex management infrastructure

•  Difficult to initially learn to create •  Consumes a lot of CPU time

SOA •  A Service Oriented Architecture aims create and use

small pieces of software to accomplish a greater goal

•  Services are the small pieces of software used as building blocks

•  A client is any piece of software that is written to use a service for some functionality

•  A registry is a server that hosts information about web services so that clients can find web services

SOA

Services •  Individual software systems that can be

queried by other software

•  Implementation has two parts:

•  The logic of the services

•  The service messaging system

•  Important to consider how a service will message a client

Service Design Principles

•  Services should be a small unit of software with a distinct goal or purpose

•  Allows for easier reuse

•  If you want your service to accomplish some significant task, consider writing more than one service

•  Decouple the Messaging and the logic as much as possible

•  If you change your service, you don’t want to break all of the clients that are designed to access your service

•  Implantation Details and Hosting Platform aren't important

Communication •  Communication is huge in SOA

• We have all of these services, how do they talk to clients?

•  Two different things need to be established:

•  How can we expose a services interface to clients in a convenient manner?

•  What is the format of messages sent to and from services?

Web Services Description Language (WSDL)

•  XML Language to describe a service’s interface

•  Standard document format, maintained by W3C

•  Client reads the WSDL file, and discovers:

•  What kind of requests can be sent to the service, and what the parameters and return type will be

•  Think function prototypes

•  What kind of messaging protocol must be used to send these requests

WSDL

SOAP Protocol •  An XML message protocol

•  Created by Microsoft in 1998

•  Standardize the messages sent between Client and Service

•  Can be used over any transfer protocol (HTTP, SMTP, TCP)

SOAP Protocol POST /InStock HTTP/1.1���

Host: www.example.org���Content-Type: application/soap+xml; charset=utf-8���Content-Length: nnn������< ?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:Body xmlns:m="http://www.example.org/stock">��� <m:GetStockPrice>��� <m:StockName>IBM</m:StockName>��� </m:GetStockPrice>��� </soap:Body>������< /soap:Envelope>

RESTful Web Services •  A design philosophy for creating web services

•  New Idea

•  RESTful web services have only been around since mid 2000’s

•  REST =

•  REpresentational

•  State

•  Transfer

•  REST was defined by Roy Fielding, Creator of HTTP, in 2000.

RESTful Web Services •  Key RESTful Concepts:

•  Separate the concerns of the client and the service

•  System should be stateless. No client information needs to be stored by the service

•  Must implement a uniform interface between client and server, usually uses HTTP’s methods (GET, POST, PUT, DELETE)

RESTful Web Services •  How does this actually work?

•  The service has some resources or data that it would like to expose to client systems

•  The web server is set up to give URIs to each of these resources or data

•  Eg: http://www.myservice.org/discussion/topics/1

•  A client may now retrieve that piece of information from the service by sending an HTTP GET request to that URI

•  The service sends back a very simple XML or JSON file containing only the information asked for

SOAP vs. RESTful Web Services

•  Current debate in development community

•  If im making a web service, should I use SOAP, or make it a RESTful web service?

SOAP vs. RESTful Web Services

•  RESTful Advantages:

•  Lightweight: No need for extensive XML Markup. Messages are much smaller.

•  Can return anything as a response message, so things like JSON can be used

•  No extensive toolkits are required to create

SOAP vs. RESTful Web Services •  SOAP Advantages:

•  Language, Platform and Transport independent

•  Built in error handling

•  Strong typing guarantees type security

•  Built to handle distributed computing enviroments

•  Robust tool support

•  Various security extensions have been developed for SOAP

SOAP vs. RESTful Bottom Line •  RESTful Web Services are easy to get off the ground

and provide most of the functionality of SOAP

•  If you can use RESTful, you probably should

•  SOAP still has uses

•  Non web based SOA systems

•  Distributed computing enviroments

•  Some critical security extensions

External Facing Services

•  Integration •  Available through public API

Google Translate API

GET https://www.googleapis.com/language/translate/v2?key=&source=en&target=de&q=Hello%20world

200 OK { "data": { "translations": [ { "translatedText": "Hallo Welt" } ] } }

The Cloud •  Storage

•  Computing (SaaS)

•  Servers

Case Study: eBay 2 500 000 000 Hits on a busy

day

2 000 000 000 000 000 bytes of data

6 000 000 lines of code

100 000 new lines of code every two weeks

30 000 software builds per week

Internal Facing Services

Case Study: eBay •  Helped to solve the complexity

issues •  Helped to solve many other

technical problems such as interoperation between C++ and Java

•  Greatest benefit was in management

Case Study: eBay •  Business Agility

o  Produced new features faster

o  Quicker response to change o  Easier integration with partners

•  Innovation o  Enabled internal and external innovation

•  Operational Excellence o  Reduced cost for new features o  Efficient resource utilization o  Reduced cost of failure

Benefits

Case Study: eBay Challenges

•  Learning Curve •  Governance •  Migration •  Deployment •  Metrics •  Integration Testing

Tech Talk •  Service is big on sharing, and sharing requires

adherence to standards.

•  SOA grants freedom to choose language.

•  All major languages have SOA libraries. •  Java SOAP: JAX-WS, JAX-PRC, Axis •  Java REST: RESTlet, Jersey •  C# SOAP: Web Reference, Service References •  C# REST: OpenRasta •  Python SOAP: SUDS, soaplib, pysimplesoap •  Python REST: built-in web libraries suffice (guide)

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Tech Talk

Die-hard Fundamentalist

DIY Vimer?

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Tech Talk • Many IDE have SOA development tools & plugins

•  Technologies change often, search for the latest

•  To get a quick start, finding a toolkit that has up-to-date documentation is important.

•  For this quick demo, I decided to use •  Java •  SOAP •  Oracle JDeveloper with JAX-WS

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Registry •  There are very few open registry for free-lance

developers to publish their services.

•  Large-corporations often host their own closed service registries.

•  Maybe open to the public to consume

•  But do not allow public publishing service

•  JDeveloper integrated WebLogic Server to host & test services locally.

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ESB • ESB - Enterprise service bus

• The prime duties of an ESB are:

•  Monitor and control routing of message exchange between services

•  Resolve contention between communicating service components

•  Control deployment and versioning of services

• Popular ESB: webMethods, Mule

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Publishing •  Since input parameters and return value will

be serialized into XML, their type must be •  Primitive types: int, float, double

•  Primitive type Wrappers: Integer, Double

•  Strings

•  A Java bean with a zero-argument constructor, with a pair of "get" and "set" methods for each property to be exposed.

•  Array of those types

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Publishing •  Bottom-up

•  Work with existing software, turn into services

•  Some say it’s better for updating legacy systems

•  Top-down •  Design and create interfaces first, then implement

•  Some say it promotes more reuse, but may require organization-wide change.

• On-going debate

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Bottom-up Code before

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Bottom-up Code after

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Testing with HTTP analyzer

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Bottom-up

Testing with HTTP analyzer

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Testing with HTTP analyzer

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Testing with HTTP analyzer

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Flow of Data

Top-down From WSDL, use wizard to generate code stub

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Top-down From WSDL, use wizard to generate code stub

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Top-down Implement method

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Consuming •  Discovering and binding of services

•  Technologies: UDDI, ebXML, WSIL

•  Facilitate discovery

•  Automated, and dynamic by using simple API

•  Example: JAXR - Java API for XML Registries

•  Tools generate local wrapper method/functions for the service

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Consuming Wizard to generate local wrapper methods

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Consuming Specify WSDL location – step may be automated

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Generated code

Consuming

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Consuming Using service by calling wrapper method

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Key Points to Remember •  Comm. Standards are important. (SOAP, REST)

•  Lots of technologies to choose from. There will be libraries to help you do SOA.

•  Provider vs. Registry vs. Consumer

•  Only use parameters that can be serialized to XML when creating services

•  Top-down vs. Bottom-up approach •  Service discovery & binding. Local wrapper.

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