Java IoT Authors: Yeshim Deniz, Elizabeth White, Roger Strukhoff, Liz McMillan, Pat Romanski

Related Topics: Java IoT

Java IoT: Article

SOA Web Services - Data Access Service

How to access relational data in terms of Service Data Objects

Service Data Objects (SDOs) have become a foundation technology for Service Oriented Architecture (SOA). Recently, BEA, IBM, Oracle, SAP, Iona, Siebel, and Sybase announced their support for an SOA-enabling framework specification named Service Component Architecture (SCA). SD O provides the primary data representation in this framework.

Although not addressed by the current SDO or SCA specifications, there's a definite need for a generic data access service that operates in terms of SDOs. The alternative to this service would be the tedious and error-prone development of a custom mapping between the back-end data representation and Service Data Objects.

The Relational Database Data Access Service (RDB DAS) obviates the need for this custom development by providing a robust data access utility built around SDO. Because of its tight integration with SDO, the RDB DAS is also a perfect solution for data access in an SCA-based application.

By employing the RDB DAS, applications avoid the details and complications of working directly with a relational database and also the complex transformation between relational rows/columns and Data Object types/properties.

Since the release of the specification in late 2003, SDO has proven itself a flexible and robust technology for data representation. Its inherent support for disconnected operations and heterogeneous data sources offers strong support for the needs of modern software architectures. For these reasons, SDO has found its way into several commercial products from major vendors and these same characteristics have led to its inclusion in SCA as a foundation technology.

SDO provides the general case mechanism for moving data around an SCA-enabled application. However, the reality is that most of this data must originate in some database at one edge of the application and be stored in some database at another edge. Unfortunately, database access isn't currently either SDO or SCA. (An early version SDO Data Access Service specification is in progress.)

This leaves the developer with a serious undertaking since there's a fundamental mismatch between the objects that an application works with and the tables and rows of a relational database that provide the persistent store for the object's state (see http://en.wikipedia.org/wiki/object-relational_impedance_mismatch).

For example, let's consider a simple query against a relational database for customers in a certain age range and their related orders.

An SDO-enabled application could most easily and naturally work with a normalized graph of Data Objects representing the query. Figure 1 illustrates this graph of connected Data Objects.

This in-memory graph of data objects brings to bear all of the capabilities of SDO.

  • It's a disconnected representation of the queried data
  • It provides simple traversal between related elements
  • It tracks all changes from its original form via the SDO change summary
  • It contains no redundant information
  • It's easily serialized to XML
But unfortunately the relational database returns a tabular representation of the query result complete with redundant customer information as shown in Figure 2.

The transformation required to convert from tabular format to a graph of interconnected data objects is complicated and the reverse (transforming graph changes to a sequence of SQL inserts/updates and deletes) is even more so.

Because of the difficulties inherent in the transformation between the database and the application object space, an application development project can easily spend a third of its development resources on functions related to moving object state in and out of the database.

Business application developers shouldn't be burdened with this task and should instead be allowed to focus on business functionality.

The RDB DAS offers a solution to the problems mentioned above by providing two major capabilities. The RDB DAS can:

  1. Execute SQL queries and return results as a graph of Data Objects
  2. Reflect changes made to a graph of Data Objects back to the database
Figure 3 illustrates these two capabilities in a typical client interaction. The client starts by reading a graph of data specified by some query. The client then makes modifications to the graph, possibly by adding elements, and then requests the DAS to push the changes back to the database.

The DAS provides an intuitive interface and is designed so that simple tasks are simple to complete while more complicated tasks are just a little less simple.

The application interface to the DAS is based on the familiar Command Pattern and interaction with the DAS consists of acquiring command instances and executing them (see Design Patterns by Erich Gamma, et al). The following example demonstrates the simplest possible read of data.

Command read = Command.FACTORY.createCommand("select * from CUSTOMER where ID = 10021");
DataObject root = read.executeQuery();

In this case the command is created programmatically from a Command factory and the only input necessary is the SQL SELECT statement. Executing the read command returns the root of the resulting data graph and data can be extracted from the graph using the SDO dynamic API.

String lastName = root.getString("CUSTOMER[1]/LASTNAME");

Pushing changes back to the database can be equally straightforward. Continuing with this example we can modify the customer object and then direct the DAS to send the modifications to the database. This line uses the SDO dynamic API to change the last name of the retrieved customer.

root.setString ("CUSTOMER[1]/LASTNAME", "Williams");

Now that we have a modified graph, we can synchronize the changes with the database by passing the data graph to an "apply changes command" and asking it to execute.

ApplyChangesCommand apply = Command.FACTORY.createApplyChangesCommand();

As you may have noticed, the read and write examples each required three lines of code (except the code to get the connection object). So those of you familiar with O/R frameworks might be asking yourself a few questions. What is going on here? Where did you define all the configuration data? I didn't see a deployment descriptor? Where is the object-relational mapping information? Where are the static domain classes like Customer? The answers to these questions are based on two significant SDO capabilities and one design philosophy:

  • Dynamic SDO
  • SDO Change History
  • DAS use of convention
Dynamic SDO
The reason you don't see a Customer interface or class used in this example is because the DAS can work with dynamic SDO data objects. This is a very powerful and often overlooked SDO capability.

Many applications today use the Transfer Object(TO) pattern to move data around tiers within an application (see Core J2EE Patterns by Deepak Alur, et al). Since these TOs typically have no behavior, there's little justification for Java interfaces and classes to implement the TO. These artifacts just represent more code to write, maintain, and manage.

One argument for TOs as Java interfaces/classes is the potentially cleaner API:

Static API
customer.setLastName("Williams") Dynamic API
customer.setString("lastName", "Williams")

However, the SDO dynamic API is straightforward and can even be simpler to read than a static equivalent. For example, we can use the SDO XPath capability to access properties like this:

amount = customer.getFloat("orders[17]/price");

The equivalent, with normal static Java APIs, would look something like this:

amount = ((Order)customer.getOrders().get(17)).getPrice();

The dynamic API can also be useful in applications where the data model is likely to change often during development. It lets developers use the full breadth of Data Object function without having to generate a new static model (Java classes and interfaces) every time a change is made.

SDO Change History
The change history feature of SDO data graphs is another reason that SDO data objects can be thought of as transfer objects on steroids. Not only do data objects provide a snappy dynamic API and XML serialization, SDO data objects also remember any changes that have been made to them.

The change history capability means that SDO data objects aren't dependent on a container or some persistence manager to track their state. In fact, since the change history is serialized along with the associated data objects, a graph of SDO data objects can flow through different tiers of a distributed application remembering all the changes that may occur along the way. Later, when it's time to reflect those changes back to the database, the DAS can process the change history and build the set of create/update/delete commands needed to flush the accumulated changes.

The Change History tracks changes made to all data object properties including fields and relationships. Using this information, the DAS can handle the complex task of reflecting object graph changes back to the database without exposing this complexity to users. The DAS translates object property changes into database column updates and object relationship changes into database foreign key updates.

Use of Convention over Configuration
The DAS makes use of convention to simplify the programming model. For instance, in the simple read example above we have this statement to access the last name of a customer:

String lastName = root.getString("CUSTOMER[1]/LASTNAME");

Notice the path name: "CUSTOMER[1]/LASTNAME". This suggests that there is an SDO Type named CUSTOMER with a property named LASTNAME. If you remember, the command used to read this data was created like this:

Command read = Command.FACTORY.createCommand("select * from CUSTOMER where ID = 10021");

The RDB DAS, by convention, creates an SDO Type for each database table represented in the query result. In addition, it creates a property for each table column represented in the query result. In the absence of any additional configuration data, the names of these Types and Properties will exactly match the names of the database Tables and Columns. So given the SELECT statement above and the knowledge that the CUSTOMER table has a column named LASTNAME, we can assume that the data graph returned will be populated with instances of Type CUSTOMER that have a property LASTNAME. This capability is made possible by using the metadata associated with the ResultSet returned from the query execution.

If the application developer wants the names of Types and Properties to vary from the names of the Tables and Columns then he or she can override this convention with a bit of configuration. We'll get into the details of providing configuration to the DAS a little later.

Another bit of convention that this example demonstrates is exploited when flushing graph changes to the database:

ApplyChangesCommand apply = Command.FACTORY.createApplyChangesCommand();

In the absence of instruction (configuration) to do otherwise, the DAS will scan the change history and generate the create/update/delete (CUD) statements necessary to flush the changes to the database. Since we just changed a single property of a single data object, the change history processing produces a single statement to be executed:

update CUSTOMER set LASTNAME = 'Williams' where ID = 10021

More Stories By Kevin Williams

Kevin Williams is a software developer with IBM and is leading IBM’s participation in the DAS subproject of the Apache Tuscany incubator.

More Stories By Brent Daniel

Brent Daniel is a software developer with IBM. He currently works on a JDBC data mediator service for WebSphere Application Server.

Comments (4) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

Most Recent Comments
Augustine J. Cannata 09/20/06 11:32:55 AM EDT

what about stored procedures?

n d 08/27/06 03:31:45 PM EDT

Service Data Objects (SDOs) have become a foundation technology for Service Oriented Architecture (SOA). Recently, BEA, IBM, Oracle, SAP, Iona, Siebel, and Sybase announced their support for an SOA-enabling framework specification named Service Component Architecture (SCA). SD O provides the primary data representation in this framework.

n d 08/27/06 12:15:18 PM EDT

Service Data Objects (SDOs) have become a foundation technology for Service Oriented Architecture (SOA). Recently, BEA, IBM, Oracle, SAP, Iona, Siebel, and Sybase announced their support for an SOA-enabling framework specification named Service Component Architecture (SCA). SD O provides the primary data representation in this framework.

n d 08/27/06 11:33:13 AM EDT

Service Data Objects (SDOs) have become a foundation technology for Service Oriented Architecture (SOA). Recently, BEA, IBM, Oracle, SAP, Iona, Siebel, and Sybase announced their support for an SOA-enabling framework specification named Service Component Architecture (SCA). SD O provides the primary data representation in this framework.

@ThingsExpo Stories
Digital Transformation: Preparing Cloud & IoT Security for the Age of Artificial Intelligence. As automation and artificial intelligence (AI) power solution development and delivery, many businesses need to build backend cloud capabilities. Well-poised organizations, marketing smart devices with AI and BlockChain capabilities prepare to refine compliance and regulatory capabilities in 2018. Volumes of health, financial, technical and privacy data, along with tightening compliance requirements by...
As IoT continues to increase momentum, so does the associated risk. Secure Device Lifecycle Management (DLM) is ranked as one of the most important technology areas of IoT. Driving this trend is the realization that secure support for IoT devices provides companies the ability to deliver high-quality, reliable, secure offerings faster, create new revenue streams, and reduce support costs, all while building a competitive advantage in their markets. In this session, we will use customer use cases...
Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life settlement products to hedge funds and investment banks. After, he co-founded a revenue cycle management company where he learned about Bitcoin and eventually Ethereal. Andrew's role at ConsenSys Enterprise is a mul...
DXWorldEXPO LLC announced today that "Miami Blockchain Event by FinTechEXPO" has announced that its Call for Papers is now open. The two-day event will present 20 top Blockchain experts. All speaking inquiries which covers the following information can be submitted by email to [email protected] Financial enterprises in New York City, London, Singapore, and other world financial capitals are embracing a new generation of smart, automated FinTech that eliminates many cumbersome, slow, and expe...
DXWorldEXPO | CloudEXPO are the world's most influential, independent events where Cloud Computing was coined and where technology buyers and vendors meet to experience and discuss the big picture of Digital Transformation and all of the strategies, tactics, and tools they need to realize their goals. Sponsors of DXWorldEXPO | CloudEXPO benefit from unmatched branding, profile building and lead generation opportunities.
The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
DevOpsSummit New York 2018, colocated with CloudEXPO | DXWorldEXPO New York 2018 will be held November 11-13, 2018, in New York City. Digital Transformation (DX) is a major focus with the introduction of DXWorldEXPO within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of bus...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, we provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading...
Cloud Expo | DXWorld Expo have announced the conference tracks for Cloud Expo 2018. Cloud Expo will be held June 5-7, 2018, at the Javits Center in New York City, and November 6-8, 2018, at the Santa Clara Convention Center, Santa Clara, CA. Digital Transformation (DX) is a major focus with the introduction of DX Expo within the program. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive ov...
DXWordEXPO New York 2018, colocated with CloudEXPO New York 2018 will be held November 11-13, 2018, in New York City and will bring together Cloud Computing, FinTech and Blockchain, Digital Transformation, Big Data, Internet of Things, DevOps, AI, Machine Learning and WebRTC to one location.
DXWorldEXPO LLC announced today that ICOHOLDER named "Media Sponsor" of Miami Blockchain Event by FinTechEXPO. ICOHOLDER give you detailed information and help the community to invest in the trusty projects. Miami Blockchain Event by FinTechEXPO has opened its Call for Papers. The two-day event will present 20 top Blockchain experts. All speaking inquiries which covers the following information can be submitted by email to [email protected] Miami Blockchain Event by FinTechEXPO also offers s...
Dion Hinchcliffe is an internationally recognized digital expert, bestselling book author, frequent keynote speaker, analyst, futurist, and transformation expert based in Washington, DC. He is currently Chief Strategy Officer at the industry-leading digital strategy and online community solutions firm, 7Summits.
Digital Transformation and Disruption, Amazon Style - What You Can Learn. Chris Kocher is a co-founder of Grey Heron, a management and strategic marketing consulting firm. He has 25+ years in both strategic and hands-on operating experience helping executives and investors build revenues and shareholder value. He has consulted with over 130 companies on innovating with new business models, product strategies and monetization. Chris has held management positions at HP and Symantec in addition to ...
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...
Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities - ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups.
The standardization of container runtimes and images has sparked the creation of an almost overwhelming number of new open source projects that build on and otherwise work with these specifications. Of course, there's Kubernetes, which orchestrates and manages collections of containers. It was one of the first and best-known examples of projects that make containers truly useful for production use. However, more recently, the container ecosystem has truly exploded. A service mesh like Istio addr...
Predicting the future has never been more challenging - not because of the lack of data but because of the flood of ungoverned and risk laden information. Microsoft states that 2.5 exabytes of data are created every day. Expectations and reliance on data are being pushed to the limits, as demands around hybrid options continue to grow.
Business professionals no longer wonder if they'll migrate to the cloud; it's now a matter of when. The cloud environment has proved to be a major force in transitioning to an agile business model that enables quick decisions and fast implementation that solidify customer relationships. And when the cloud is combined with the power of cognitive computing, it drives innovation and transformation that achieves astounding competitive advantage.
Poor data quality and analytics drive down business value. In fact, Gartner estimated that the average financial impact of poor data quality on organizations is $9.7 million per year. But bad data is much more than a cost center. By eroding trust in information, analytics and the business decisions based on these, it is a serious impediment to digital transformation.
With tough new regulations coming to Europe on data privacy in May 2018, Calligo will explain why in reality the effect is global and transforms how you consider critical data. EU GDPR fundamentally rewrites the rules for cloud, Big Data and IoT. In his session at 21st Cloud Expo, Adam Ryan, Vice President and General Manager EMEA at Calligo, examined the regulations and provided insight on how it affects technology, challenges the established rules and will usher in new levels of diligence arou...