lihongjie0209
commented
3 years ago Channel Adapter
A channel adapter is an endpoint that connects a message channel to some other system or transport. Channel adapters may be either inbound or outbound. Typically, the channel adapter does some mapping between the message and whatever object or resource is received from or sent to the other system (file, HTTP Request, JMS message, and others). Depending on the transport, the channel adapter may also populate or extract message header values. Spring Integration provides a number of channel adapters, which are described in upcoming chapters.
Service Activator
A Service Activator is a generic endpoint for connecting a service instance to the messaging system. The input message channel must be configured, and, if the service method to be invoked is capable of returning a value, an output message Channel may also be provided.
The service activator invokes an operation on some service object to process the request message, extracting the request message’s payload and converting (if the method does not expect a message-typed parameter). Whenever the service object’s method returns a value, that return value is likewise converted to a reply message if necessary (if it is not already a message type). That reply message is sent to the output channel. If no output channel has been configured, the reply is sent to the channel specified in the message’s “return address”, if available.
A request-reply service activator endpoint connects a target object’s method to input and output Message Channels.