学习 spring mvc 的过程中，发现他的 controller 的函数的入参很是神奇，变化多端，捉摸不定，查了一下，这里有说：http://stackoverflow.com/questions/8372957/how-does-spring-mvc-controller-method-parameter-work
The general answer is “Spring magic”; however, “Supported handler method arguments and return types” in the MVC chapter of the Spring reference guide has the exact answers to your questions.
在这里 http://stackoverflow.com/questions/12696222/spring-mvc-controller-method-signatures 和这里 http://docs.spring.io/spring/docs/3.1.x/spring-framework-reference/html/mvc.html#mvc-ann-arguments 可以看到更详细的说明