Spring ContentNegotiatingViewResolver

1. Spring 返回视图采用了ViewResolver，如果一般是jsp的话，可以采用InternalResourceViewResolver。

2.还可以通过ContentNegotiatingViewResolver来返回不同种类的视图，具体是是根据MediaTypes。

3. 一共有三种方式：使用扩展名、使用http request header的Accept、使用参数

他们直接的关系是：

1. If the requested path has a file extension and if the setFavorPathExtension(boolean) property is true, the mediaTypes property is inspected for a matching media type.
2. If the request contains a parameter defining the extension and if the setFavorParameter(boolean) property is true, the mediaTypes property is inspected for a matching media type. 

The default name of the parameter is format and it can be configured using the parameterName property.
3. If there is no match in the mediaTypes property and if the Java Activation Framework (JAF) is both enabled and present on the class path, FileTypeMap.getContentType(String) is used instead.
4. If the previous steps did not result in a media type, and ignoreAcceptHeader is false, the request Accept header is used.
Once the requested media type has been determined, this resolver queries each delegate view resolver for a View and determines if the requested media type is compatible with the view's content type). The most compatible view is returned.