Why the Data Management Service is useful

The Data Management Service lets you reduce the amount of code required to write a rich Internet application. You can write most of the code in a declarative style in XML. Using the Data Management Service, you can quickly and easily build and maintain applications, and enhance collaboration between programmers and designers. This method also provides features such as on-demand paging, synchronization of data between client, server, and other clients for improved access to information and collaboration. You can also make data available offline. The Data Management Service is built on the LiveCycle Data Services ES message-based framework, a flexible, efficient and scalable framework that integrates seamlessly with existing J2EE and ColdFusion server environments.

When you use the Data Management Service, changes to data at the Flex client side are automatically sent to the Data Management Service running in your application server. The Data Management Service then passes the changes to your business layer or directly to your persistence layer, which are data access objects (DAOs) with straight JDBC calls, Hibernate, Java Persistence API (JPA), or any other solution. By using the Data Management Service, you can avoid writing data synchronization code in your Flex client application.

Depending on the type of application you are building, the Data Management Service can save you from having to write a great deal of client-side code in the following scenarios:

• Keeping track of all the items created, updated, and deleted by the user at the client side.
• Keeping track of the original value of the data as initially retrieved by the client. The persistence layer often needs the original value to implement optimistic locking.
• Making a series of RPC calls to send changes (creates, updates, deletes) to the middle tier.
• Handling the conflicts that arise during this data synchronization process.

Comparing the Data Management Service and RPC approaches

The Data Management Service uses an approach to data that is fundamentally different from the remote procedure call (RPC) approach. Unlike the RPC approach, the Data Management Service supports automatic and manual synchronization of a common set of data on multiple clients and server-side data resources. The client automatically tracks changes made to these objects and can apply those changes on the server objects. The server can then update any clients viewing these same objects. It also supports offline client-side data persistence.

Flow of data between clients and the server

The Data Management Service uses the LiveCycle Data Services ES message-based framework, which passes data messages between Flex client applications and the Data Management Service. Data Management Service client applications act as both message producers and consumers that send data to a Data Management Service destination and subscribe to the destination to receive data updates.

The primary client-side object you use with the Data Management Service is the DataService component. You can create a DataService component in MXML or ActionScript, and call methods on a Data Management Service destination. The DataService component performs activities such as filling client-side objects with data from remote data resources, committing data changes to the server, and detecting data synchronization conflicts. For more information, see Data Management Service clients.

Changes to data on the client are tracked and sent to the Data Management Service destination when you choose to commit them. If successfully applied, they are propagated to other clients.

The following image shows the flow of data between a back-end data resource and an ArrayCollection object that a DataService component manages in a Flex application: