All <section/> elements in beans.xml >=~ 500 lines have been broken out
into separate documents with DOCTYPE 'section'. This refactoring makes
working with these files much easier in wysiwyg editors (namely
oXygen Author).

For consistency, this same refactoring should be applied to all other
chapters much larger than 1500 lines, such as aop.xml (3861), mvc.xml
(3466), jdbc.xml (3042), and so on.

beans.xml and the new section files have also been formatted for
consistency and to avoid whitespace diffs as much as possible into the
future.

revised constructor argument caching for highly concurrent creation scenarios (follow-up to SPR-7423)

JavaDoc and reference docs now warn developers against interacting with
bean instances within BeanFactoryPostProcessor implementations in order
to avoid premature bean instantiation.

See SPR-7450 for an example of a third-party BFPP
(OAuthTokenLifecycleRegistryPostProcessor) prematurely instantiating
a FactoryBean instance, such that bean post-processing is bypassed
and autowired injection (via @Inject) never occurs.

consistent converting and escaping of label values (following AbstractMultiCheckedElementTag's SPR-7174)

WebDataBinder and @mvc request param binding detect and introspect MultipartFile arrays as well (SPR-2784)

Servlet/PortletContextResource inherit isReadable, contentLength and lastModified from AbstractFileResolvingResource

CommonsMultipartResolver cleans up all multipart files in case of multiple files for same name as well (SPR-2784)

WebDataBinder and @mvc request param binding detect and introspect MultipartFile arrays as well (SPR-2784)

revised DispatcherServlet's last-modified handling to properly work with scoped controllers; added HEAD support to ResourceHttpRequestHandler

introspect superclass when given a CGLIB proxy as target class (SPR-7448); use generic Class<?> in TransactionAttributeSource signature