Spring Framework 4.0 M2 发布：支持WebSocket的消息架构

可以利用WebSocket API实现WebSocket风格的消息应用。

Spring Framework 4.0的第一个里程碑提供了SockJS的服务器端支持， the best and the most comprehensive WebSocket browser fallback options. You will need fallback options in browsers that don't support WebSocket and in situations where network proxies prevent its use. Simply put SockJS enables you to build WebSocket applications today and rely on transparent fallback options when necessary.

Even with fallback options, bigger challenges remain. A socket is a very low-level abstraction and the vast majority of web applications today do not program to sockets. This is why the WebSocket protocol defines a sub-protocol mechanism that essentially enables, and encourages, the use of higher-level protocols over WebSocket, much like we use HTTP over TCP.

The second milestone of Spring Framework 4.0 enables the use of higher-level messaging protocols over WebSocket. To demonstrate this we've put together a sample application.

Stock Portfolio Sample

The Stock Portfolio sample application, available on Github, loads a user's portfolio positions, allows buying and selling shares, consumes price quotes, and displays position updates. It is a reasonably simple application. Yet it handles a number of common tasks that are likely to come up in browser-based messaging applications.

So how do we put together an application like that? From HTTP and REST we are used to relying on URLs along with HTTP verbs to express what needs to be done. Here we have a socket and lots of messages. How do you tell who a message is for and what the message means?

Browser and server must agree on a common message format before such semantics can be expressed. Several protocols exist that can help. We chose STOMP for this milestone due to its simplicity and wide support.

英文详细内容：http://blog.springsource.org/2013/07/24/spring-framework-4-0-m2-websocket-messaging-architectures/