Flash Player and Adobe AIR don't have the capabilit to communicate directly with server-based data storage applications such as database and Lightweight Directory Access Protocol(LDAP) servers. Instead, they're designed to communicate with middleware application servers using a variety of protocols.HTTPService component has the most flexibility in terms of format of messages that are exchanged between the client and server at runtime. you can use the HTTPService component with any applicaiton server,because it exchanges data in the form of simple HTTP parameters and XML of an flavor.
RPC and REST are acronyms that represent architectural styles.
REST stands for Representational Stare Transfer, and it represents a software architecture or design pattern that can be implemented with numerous client-based and server-based platforms for the web. A "RESTful" architecture enables a local client system to retrieve resources stored in a remote system without necessarily requiring a remote dynamic application server.
RPC represents a software architecture that enables a computer program in one operating environment to cause functions to be executed in separate, remote operating environments.RPC-style architectures are typically implemented in Flex with a dynamic Web server that can respond to complex HTTP requests.
HTTPService component: makes standard HTTP requests to any Web server environment, and uses eigher plain text or any well-formed XML language as its message format.
RemoteObject: communicates with application servers using the binary AMF
WebService: makes requests to and handles responses from application servers that support the industry-standard SOAP message format
after connect to HTTP in the connect to Data/Service dialog box, you will the data/services view has been actived.
When data is returned from an HTTPService request, it's defined by default as an ActionScript Object.
Essential HTTPService properties
the HTTPService component implements these properties that determine where the request is made and what HTTP methods are used:
concurrency:String. a rule that determines how to handle multiple concurrent calls to the same network resource
method:String: the HTTP method to be used
resultFormat:String
showBusyCursor:Boolean
url:String the web address to which the request is sent
Handling the result event:
When data is returned from the remote server, the HTTPService object dispatches a result event, whose event object is typed as mx.rpc.events.resultEvent. this reusltevent class has a result property that refers to the returned data.