Welcome!

Adobe Flex Authors: Matthew Lobas, PR.com Newswire, Shelly Palmer, Kevin Benedict

Related Topics: Adobe Flex

Adobe Flex: Article

End-to-End Rapid Application Development with Data Services & Adobe Flex

Excerpts from Chapter 6 of Rich Internet Applications With Adobe Flex & Java

The simplest way to explain Flex Data Services (FDS) is to compare them with Flex Remoting. Simply put, FDS addresses only a subset of operations facilitated via Flex Remoting - result set requests. However, whereas Flex Remoting enables one-way requests, FDS combines one-way requests with the publish/subscribe mechanism so that besides the original result set FDS sends the client live updates produced by other clients of the same destination. And there's one more dimension in which Data Services depart from Flex Remoting - support for hierarchical collections, but we won't be covering that subject in this book.

In other words, FDS resolves the task of programming data collaboration: Several users may edit different rows and columns of the "same" DataGrid and see each other's changes automatically pushed by the server. Now, what if they overlap each other's work? In terms of FDS that's called a conflict and the FDS API provides for flexible conflict resolution, which may require the user's intervention.

An FDS destination can be configured for working with the data that is persisted to a data store as well as supporting scenarios that persist the data in the server's memory. To that end, FDS provides Java and ActionScript data adapters that are responsible for reading and updating a persistent data store according to its type. In this chapter we'll focus on use cases involving Java adapters.

Flex Data Services & Automation: Problem Statement & Solution
Robust in enabling collaborative manipulation of data, FDS demands a substantial development effort in case of persistent data stores. In particular, you need to build:

  • A Java Data Access Object class that implements retrieve, update, delete, and insert of the data;
  • Java Data Transfer Objects (DTO);
  • A matching ActionScript data transfer object class;
  • A configuration file, which registers identity columns of the result set and, optionally, argument types for every retrieval method and other parameters.
We just mentioned four classes/files containing hard-coded names of the fields and there are more. To function properly, these hard-coded values have to be kept in sync, which is an additional maintenance effort whenever the data structures change.

Addressing this complexity, the main idea of this chapter is not to cover every twist of the FDS API, but rather automate the development effort that FDS takes for granted. We'll start with a "manual," albeit simplified, example of using DataServices. Then we'll introduce you to the methodology of complete code generation based on the pre-written XSL templates and FDS-friendly XML metadata, which will be extracted from the annotated Java abstract classes.

This methodology is fully implemented in DAOFlex - an Open Source utility that's a complementary addition to this book. We'll gradually introduce this tool by leading you through a process of creating the most comprehensive template that generates a complete DataServices Data Access Object DAO. Finally, we'll show you how to run and customize DAOFlex in your development environment so that writing and synchronizing routine DataServices support classes becomes a task of the Ant building tool and not yours!

A "Manual" FDS Application
Let's handcraft the application presented in Figure 6.1. This application displays a Panel with a scrollable DataGrid that we consciously did not size in the horizontal dimension, so that all columns can be viewed without shrinking. The database result set is ultimately produced by the following SQL query that will use a bound variable in place of the question mark:

    select * from employee where start_date < ?

There are two buttons below the DataGrid: Fill and Commit. As the names imply, these buttons pull the original data from the database table and submit the data changes back to an FDS destination. A separate Parameters panel permits entering parameters of the back-end method behind the Fill button, which, in our case, is the employee start date :

Building the Client Application
Let's build the client application first. The full listing of the application is presented in Listing 6.1. We start with defining the mx:DataServices object (a k a ds), which points to the destination "Employee." Later, when we get to the server components we'll discuss mapping this destination to the backing Java class:

    <mx:DataService id="ds" destination="Employee" fault="onFault(event)" />

We provide only a rudimentary handler of the fault event that's sufficient to keep us aware of any anomalies that may occur along the way. Dynamic referencing fault and faultString properties will spare us from casting to a specific event:

    private function onFault(evt:Event):void {
       Alert.show(evt["fault"]["faultString"], "Fault");
    }

Then we define a handler of the application's onCreationComplete event where we instantiate a collection to be eventually associated with our mx:DataService object and, most importantly, set both autoCommit and autoSyncEnabled of the ds to false:

    private function onCreationComplete() : void {
       collection = new ArrayCollection();
       ds.autoCommit=false;
       ds.autoSyncEnabled=false;
    }

By setting autoCommit to false we state that all updates have to be batched and explicitly submitted to the server as a single transaction during the ds.commit() call. By setting autoSyncEnabled to false we effectively protect our local instance of data from delivery of messages caused by other clients connected to destination "Employee." Setting autoSyncEnabled to false is entirely optional, and we use it to avoid dealing with application specific conflict resolution. In particular, in the handler of the Commit button's click event you might uncomment the first line to support the "optimistic" way of handling the conflicts:

    private function commit_onClick():void {
       //ds.conflicts.acceptAllClient();
       // Optimistic conflict handling, as oppose to
       ds.conflicts.acceptAllServer();
       ds.commit();
    }

Last, we have to initiate the population of the local collection with the ds.fill() method, which we do inside the click event handler of the button Fill:

    private function fill_onClick():void {
       ds.release();
       ds.fill(collection, param_getEmployees_startDate.selectedDate);
    }

The scripting portion of the application is completed so let's build the UI. We create a DataGrid with the dataProvider bound to our collection in Listing 6.1. For brevity's sake, we didn't list all the columns here: you'll have a chance to scrutinize them in the subsequent section of this chapter.

The DataGrid and ControlBar with Fill and Commit buttons are put inside a Panel, with DataGrid's title bearing the name of the destination and a specific getEmployees method of that destination, which will ultimately be invoked during the ds.fill() call. The second panel, titled Parameters, contains a form with a single item mx:DateField. Both panels are embraced by the VDividedBox.

We've included a linkage variable of the data transfer type to ensure that the corresponding ActionScript class (EmployeeDTO) will be linked into the generated SWF file.

<?xml version="1.0" encoding="UTF-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" backgroundColor="#FFFFFF"
creationComplete="onCreationComplete()">
   <mx:DataService id="ds" destination="Employee" fault="onFault(event)" />
   <mx:VDividedBox width="800" height="100%">
    <mx:Panel title="Employee::getEmployees()" width="800" height="70%">
     <mx:DataGrid id="dg" dataProvider="{collection}" editable="true" height="100%">
      <mx:columns><mx:Array>
       <mx:DataGridColumn dataField="EMP_ID" headerText="Emp Id" />
       <mx:DataGridColumn dataField="MANAGER_ID" headerText="Manager Id" />
       <mx:DataGridColumn dataField="EMP_FNAME" headerText="Emp Fname" />
       . . . .
      </mx:Array></mx:columns>
     </mx:DataGrid>
     <mx:ControlBar>
      <mx:Button label="Fill" click="fill_onClick()"/>
      <mx:Button label="Commit" click="commit_onClick()"        enabled="{ds.commitRequired}"/>
     </mx:ControlBar>
    </mx:Panel>
    <mx:Panel title="Parameters" width="100%" height="30%">
     <mx:HBox height="100%" width="100%">
      <mx:Form label="getEmployees()">
       <mx:FormItem label="startDate:">
        <mx:DateField id="param_getEmployees_startDate" selectedDate="{new Date()}"/>
       </mx:FormItem>
      </mx:Form>
     </mx:HBox>
   </mx:Panel>
</mx:VDividedBox>
<mx:Script>
   <![CDATA[
   import mx.controls.Alert;
   import mx.collections.ArrayCollection;
   import com.theriabook.datasource.dto.EmployeeDTO;
   private var linkage:com.theriabook.datasource.dto.EmployeeDTO = null;
   [Bindable]
   private var collection : ArrayCollection;
   private function fill_onClick():void {
     ds.release();
     ds.fill(collection, param_getEmployees_startDate.selectedDate);
   }
   private function onCreationComplete() : void {
     collection = new ArrayCollection();
     ds.autoCommit=false;
     ds.autoSyncEnabled=false;
   }
   private function commit_onClick():void {
     ds.conflicts.acceptAllClient();
     ds.commit();
   }
   private function onFault(evt:Event):void {
     Alert.show(evt["fault"]["faultString"], "Fault");
   }

   ]]>
</mx:Script>
</mx:Application>


More Stories By Victor Rasputnis

Dr. Victor Rasputnis is a Managing Principal of Farata Systems. He's responsible for providing architectural design, implementation management and mentoring to companies migrating to XML Internet technologies. He holds a PhD in computer science from the Moscow Institute of Robotics. You can reach him at [email protected]

More Stories By Yakov Fain

Yakov Fain is a Java Champion and a co-founder of the IT consultancy Farata Systems and the product company SuranceBay. He wrote a thousand blogs (http://yakovfain.com) and several books about software development. Yakov authored and co-authored such books as "Angular 2 Development with TypeScript", "Java 24-Hour Trainer", and "Enterprise Web Development". His Twitter tag is @yfain

More Stories By Anatole Tartakovsky

Anatole Tartakovsky is a Managing Principal of Farata Systems. He's responsible for creation of frameworks and reusable components. Anatole authored number of books and articles on AJAX, XML, Internet and client-server technologies. He holds an MS in mathematics. You can reach him at [email protected]

Comments (0)

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.


@ThingsExpo Stories
SYS-CON Events announced today that Hitachi, the leading provider the Internet of Things and Digital Transformation, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Hitachi Data Systems, a wholly owned subsidiary of Hitachi, Ltd., offers an integrated portfolio of services and solutions that enable digital transformation through enhanced data management, governance, mobility and analytics. We help globa...
SYS-CON Events announced today that Super Micro Computer, Inc., a global leader in compute, storage and networking technologies, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Supermicro (NASDAQ: SMCI), the leading innovator in high-performance, high-efficiency server technology, is a premier provider of advanced server Building Block Solutions® for Data Center, Cloud Computing, Enterprise IT, Hadoop/...
Amazon has gradually rolled out parts of its IoT offerings in the last year, but these are just the tip of the iceberg. In addition to optimizing their back-end AWS offerings, Amazon is laying the ground work to be a major force in IoT – especially in the connected home and office. Amazon is extending its reach by building on its dominant Cloud IoT platform, its Dash Button strategy, recently announced Replenishment Services, the Echo/Alexa voice recognition control platform, the 6-7 strategic...
SYS-CON Events announced today that Juniper Networks (NYSE: JNPR), an industry leader in automated, scalable and secure networks, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Juniper Networks challenges the status quo with products, solutions and services that transform the economics of networking. The company co-innovates with customers and partners to deliver automated, scalable and secure network...
@GonzalezCarmen has been ranked the Number One Influencer and @ThingsExpo has been named the Number One Brand in the “M2M 2016: Top 100 Influencers and Brands” by Analytic. Onalytica analyzed tweets over the last 6 months mentioning the keywords M2M OR “Machine to Machine.” They then identified the top 100 most influential brands and individuals leading the discussion on Twitter.
The age of Digital Disruption is evolving into the next era – Digital Cohesion, an age in which applications securely self-assemble and deliver predictive services that continuously adapt to user behavior. Information from devices, sensors and applications around us will drive services seamlessly across mobile and fixed devices/infrastructure. This evolution is happening now in software defined services and secure networking. Four key drivers – Performance, Economics, Interoperability and Trust ...
Data is an unusual currency; it is not restricted by the same transactional limitations as money or people. In fact, the more that you leverage your data across multiple business use cases, the more valuable it becomes to the organization. And the same can be said about the organization’s analytics. In his session at 19th Cloud Expo, Bill Schmarzo, CTO for the Big Data Practice at Dell EMC, introduced a methodology for capturing, enriching and sharing data (and analytics) across the organization...
SYS-CON Events announced today that T-Mobile will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. As America's Un-carrier, T-Mobile US, Inc., is redefining the way consumers and businesses buy wireless services through leading product and service innovation. The Company's advanced nationwide 4G LTE network delivers outstanding wireless experiences to 67.4 million customers who are unwilling to compromise on ...
The explosion of new web/cloud/IoT-based applications and the data they generate are transforming our world right before our eyes. In this rush to adopt these new technologies, organizations are often ignoring fundamental questions concerning who owns the data and failing to ask for permission to conduct invasive surveillance of their customers. Organizations that are not transparent about how their systems gather data telemetry without offering shared data ownership risk product rejection, regu...
Bert Loomis was a visionary. This general session will highlight how Bert Loomis and people like him inspire us to build great things with small inventions. In their general session at 19th Cloud Expo, Harold Hannon, Architect at IBM Bluemix, and Michael O'Neill, Strategic Business Development at Nvidia, discussed the accelerating pace of AI development and how IBM Cloud and NVIDIA are partnering to bring AI capabilities to "every day," on-demand. They also reviewed two "free infrastructure" pr...
New competitors, disruptive technologies, and growing expectations are pushing every business to both adopt and deliver new digital services. This ‘Digital Transformation’ demands rapid delivery and continuous iteration of new competitive services via multiple channels, which in turn demands new service delivery techniques – including DevOps. In this power panel at @DevOpsSummit 20th Cloud Expo, moderated by DevOps Conference Co-Chair Andi Mann, panelists will examine how DevOps helps to meet th...
With major technology companies and startups seriously embracing IoT strategies, now is the perfect time to attend @ThingsExpo 2016 in New York. Learn what is going on, contribute to the discussions, and ensure that your enterprise is as "IoT-Ready" as it can be! Internet of @ThingsExpo, taking place June 6-8, 2017, at the Javits Center in New York City, New York, is co-located with 20th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry p...
With billions of sensors deployed worldwide, the amount of machine-generated data will soon exceed what our networks can handle. But consumers and businesses will expect seamless experiences and real-time responsiveness. What does this mean for IoT devices and the infrastructure that supports them? More of the data will need to be handled at - or closer to - the devices themselves.
Grape Up is a software company, specialized in cloud native application development and professional services related to Cloud Foundry PaaS. With five expert teams that operate in various sectors of the market across the USA and Europe, we work with a variety of customers from emerging startups to Fortune 1000 companies.
Financial Technology has become a topic of intense interest throughout the cloud developer and enterprise IT communities. Accordingly, attendees at the upcoming 20th Cloud Expo at the Javits Center in New York, June 6-8, 2017, will find fresh new content in a new track called FinTech.
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 20th Cloud Expo, which will take place on June 6-8, 2017 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 add...
DevOps is often described as a combination of technology and culture. Without both, DevOps isn't complete. However, applying the culture to outdated technology is a recipe for disaster; as response times grow and connections between teams are delayed by technology, the culture will die. A Nutanix Enterprise Cloud has many benefits that provide the needed base for a true DevOps paradigm.
Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
The age of Digital Disruption is evolving into the next era – Digital Cohesion, an age in which applications securely self-assemble and deliver predictive services that continuously adapt to user behavior. Information from devices, sensors and applications around us will drive services seamlessly across mobile and fixed devices/infrastructure. This evolution is happening now in software defined services and secure networking. Four key drivers – Performance, Economics, Interoperability and Trust ...
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).