Service-oriented architecture is not just changing how we approach application integration, but the mindset of software development as well.
Applications as we know them are becoming a thing of the past. In the future we will increasingly think of services and how those services are assembled to build complete "composite" applications that can be modified easily and quickly to adapt to a continually evolving business environment.
This is the vision of a standards-based service-oriented architecture (SOA), where the IT infrastructure is continuously adapted to keep up with the pace of business change.
Oracle is at the forefront of this vision, with the Oracle SOA Suite providing the most comprehensive, proven, and integrated tool kit for building SOA based applications.
This is no idle boast. Oracle Fusion Applications (the re-implementation of Oracle's E-Business Suite, Siebel, PeopleSoft, and JD Edwards Enterprise as a single application) is probably the largest composite application being built today and it has the Oracle SOA platform at its core.
Developers and architects using the Oracle SOA Suite, whether working on integration projects, building new bespoke applications, or specializing in large implementations of Oracle Applications will need a book that provides a hands-on guide on how best to harness and apply this technology. This book will enable them to do just that.
The initial section of the book is aimed at providing the reader with an overview of the Oracle SOA Suite and its various components, followed by a hands on introduction to each of them. This will provide the reader with a good feel for each of the components and how to use them.
Once the reader is familiar with various pieces of the SOA Suite and what they do, the next question will typically be:
What is the best way to combine/use all of these different components to implement a real world SOA solution?
Answering this question is the goal of the next section. Using a working example of an online auction site (oBay), it leads the reader through key SOA design considerations in implementing a robust solution that is designed for change. It explores topics such as:
How to design sustainable service contracts, that is, ones that easily accommodate future change.
How best to leverage functionality from existing systems when building business services, while still providing flexibility to plug in an alternate service provider at a later point.
What is the right way to implement new services.
When to use rules to implement specialized services for greater flexibility.
The use of different interaction patterns and when to use each one.
Strategies for data validation and error handling, whether system errors or business errors.
Key considerations when implementing "Human Workflow".
Before an application is complete and moves from development into production, it must also meet non-functional criteria such as security, availability, and scalability requirements. The final section addresses these issues and covers considerations such as the packaging, deployment, testing, security, and administration of composite applications as well as the overall deployment of the infrastructure. Topics addressed include:
Guidelines on packaging an application for easy deployment and movement from development to the test and production environments.
Tips on building automated test suites that start at the component level and allow for testing of individual components and the complete assembly.
Where are the most effective places to apply security and what options are available for securing the system.
The book is divided into three sections. Let us have a look at these three sections in detail.
This section provides an overview of the various components of the Oracle SOA Suite and gives the reader a fast-paced, hands-on introduction to each of the key components.
Chapter 1 gives an initial tour of the constituent parts, which make up the Oracle SOA Suite as well as detailing related elements of the Oracle Fusion Middleware stack and how they relate to the SOA Suite.
Chapter 2 provides an initial look at the Oracle BPEL Process Manager and Oracle Service Bus, by stepping us through the process of developing, deploying, and running our first service.
Chapter 3 looks at a number of key technology adapters and how we can use them to service enable existing systems.
Chapter 4 describes how we can use the Oracle Service Bus to build services that are implementation agnostic. Doing so allows us to change the service location, communication protocol, or even replace a service implementation with another, with no impact on the client.
Chapter 5 describes how we can use BPEL to assemble services to build composite services as well as how we can link together a number of services to build a long-running business process. It also introduces the concepts of synchronous and asynchronous services.
Chapter 6 looks at how human tasks can be managed through workflow activities embedded within a BPEL process.
One of the key motivations behind SOA is Agility, the ability of an organization to respond rapidly to changes in market conditions and hence gain a competitive advantage.
Chapter 7 introduces the concept of externalizing "decision points" in a BPEL process as business rules, allowing us to change the flow through a process without having to make any changes to the deployed process.
Chapter 8 examines how Business Activity Monitoring (BAM) can be used to give business users a real-time view into how the business process is performing.
This section uses the example of an online auction site (oBay) to illustrate how to use the various components of the SOA Suite to implement a real-world SOA based solution.
Each chapter covers a specific area that needs to be considered when developing a SOA based solution, such as the design of the service contract, validation, error handling, and message interaction patterns.
To highlight and demonstrate key design considerations, chapters use examples based on key parts of the oBay application to illustrate what's been covered, as well as providing a step-by-step guide on how to implement these techniques.
Chapter 9 introduces oBay and details the overall business requirements of the online auction site. Next, we present our outline for a typical SOA architecture, highlighting some of the key design considerations behind this. Finally, we use this to derive the overall architecture for oBay.
The first step in building a sustainable SOA based solution, that is, one that easily accommodates future change, is careful design of the service contracts. Chapter 10 gives guidance on designing these contracts and provides strategies for managing change when it occurs.
Once we know what service we require, we need to select the appropriate way of providing it. In Chapter 11, we examine different approaches to this, either through service enabling an existing application, using someone else's service, or building the service from scratch.
A common question with SOA is "Where do I put my validation?" At first glance this may seem like an obvious question, but once we consider the layered approach to SOA, it soon becomes clear that there are a number of choices each with their own advantages and disadvantages. Chapter 12 provides us with guidelines on where to put our validation and how to implement it.
Chapter 13 examines strategies for handling errors in SOA based systems. It covers system errors such as a network connection going down meaning a web service is temporarily unavailable, and business errors such as service being invoked with invalid data.
In every business process messages are exchanged between participants. So far, we have only looked at simple interactions, that is a single request followed by a reply, whether synchronous or asynchronous.
In Chapter 14, we look at messaging in a lot more detail. In particular, how we handle more complex interactions such as multiple requests and responses, unscheduled events, timeouts, and message correlation (both system and business).
In Chapter 15, we look at workflows involving complex chains of approval, including parallel approvers and the different options that are available. We also look at how we can use the Workflow Service API to integrate workflow into a user's existing user interface as an alternative to accessing it through the out of the box worklist application.
The Rules engine uses the Rete Algorithm, which was developed by researchers into Artificial Intelligence in the 1970s. In Chapter 16, we look at some of Rete's unique qualities, and how we can use them to implement particular categories of first class business services.
When we talk about web services, most people assume that we are going to bind (that is, connect to) the service using SOAP over HTTP. Indeed, this is often the case; however, Oracle SOA Suite supports binding to web services over multiple protocols. Chapter 17 looks at the different bindings supported and the various advantages they have, including better support for transactions and improved performance.
This final section covers other considerations such as the packaging, deployment, testing, security, and administration of composite applications as well as the overall deployment of the infrastructure.
Chapter 18 examines how to package up the various artifacts that make up a composite application in order to enable easy deployment into multiple environments such as test and production. We also look at suitable deployment topologies for the SOA Suite based on run-time requirements for high availability, disaster recovery, and scalability.
Chapter 19 looks at how to create, deploy, and run test cases that automate the testing of composite applications. Testing is dealt with at several levels: unit testing, component testing, and finally assembly testing.
Chapter 20 examines how we can centrally define policies that govern the operation of web services, such as security and access policies, auditing policies, and the management of service level agreements.
The primary purpose of the book is to provide developers and technical architects with a practical guide to using and applying the Oracle SOA Suite delivering real-world SOA based applications.
It is assumed that the reader already has a basic understanding of the concepts of SOA, as well as some of the key standards in this space, including web services (SOAP, WSDL), XML Schemas, and XSLT (and XPath).
In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.
Code words in text are shown as follows: "Each schema can reference definitions in other schemas by making use of the xsd:import directive."
A block of code will be set as follows:
<types>
<schema xmlns="http://www.w3.org/2001/XMLSchema">
<import namespace="http://xmlns.oracle.com/Echo"
schemaLocation="Echo.xsd"/>
</schema>
</types>When we wish to draw your attention to a particular part of a code block, the relevant lines or items will be made bold:
<types> <schema xmlns="http://www.w3.org/2001/XMLSchema"> <import namespace="http://xmlns.oracle.com/Echo" schemaLocation="Echo.xsd"/> </schema> </types>
New terms and important words are introduced in a bold-type font. Words that you see on the screen, in menus or dialog boxes for example, appear in our text like this: "clicking the Next button moves you to the next screen".
Feedback from our readers is always welcome. Let us know what you think about this book, what you liked or may have disliked. Reader feedback is important for us to develop titles that you really get the most out of.
To send us general feedback, simply drop an email to <[email protected]>, making sure to mention the book title in the subject of your message.
If there is a book that you need and would like to see us publish, please send us a note in the SUGGEST A TITLE form on www.packtpub.com or email <[email protected]>.
If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide on www.packtpub.com/authors.
Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.
Visit http://www.packtpub.com/files/code/3551_Code.zip to directly download the example code.
The downloadable files contain instructions on how to use them.
Although we have taken every care to ensure the accuracy of our contents, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in text or code—we would be grateful if you would report this to us. By doing this you can save other readers from frustration, and help to improve subsequent versions of this book. If you find any errata, report them by visiting http://www.packtpub.com/support, selecting your book, clicking on the let us know link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata are added to the list of existing errata. The existing errata can be viewed by selecting your title from http://www.packtpub.com/support.
Piracy of copyright material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works in any form on the Internet, please provide the location address or website name immediately so we can pursue a remedy.
Please contact us at <[email protected]> with a link to the suspected pirated material.
We appreciate your help in protecting our authors, and our ability to bring you valuable content.
You can contact us at <[email protected]> if you are having a problem with some aspect of the book, and we will do our best to address it.