Spring integration building blocks 解释，基本上是从原文摘录的，懒得翻译了 ：）
Message
A message is a generic wrapper for any Java object combined with metadata used by Spring Integration to handle the object.
Headers
String/Object Map that typically maintains values for message housekeeping chores
Payloads
The message payload can be any POJO
Message Channels
A message channel is the component through which messages are moved.
Message Endpoints
A message endpoint is the abstraction layer between the application code and the messaging framework.
The main endpoint types supported by Spring Integration are as follows:
Transformer
Converts the message content or structure.
Filter
Determines if the message should be passed to the message channel.
Router
Can determine which channel to send a particular message based on its content.
Splitter
Can break an incoming message into multiple messages and send them to the appropriate channel.
Aggregator
Can combine multiple messages into one. An aggregator is more complex than a splitter often required to maintain state.
Service activator
Is the interface between the message channel and a service instance, many times containing the application code for business logic.
Channel adapter
Is used to connect the message channel to another system or transport.
Gateway
A connection that specific to bidierectional messaging
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