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public interface HandlerMapping
Interface to be implemented by objects that define a mapping between requests and handler objects.
This class can be implemented by application developers, although this is not
necessary, as BeanNameUrlHandlerMapping
and SimpleUrlHandlerMapping
are included in the framework. The former is the default if no
HandlerMapping bean is registered in the application context.
HandlerMapping implementations can support mapped interceptors but do not
have to. A handler will always be wrapped in a HandlerExecutionChain
instance, optionally accompanied by some HandlerInterceptor
instances.
The DispatcherServlet will first call each HandlerInterceptor's
preHandle
method in the given order, finally invoking the handler
itself if all preHandle
methods have returned true
.
The ability to parameterize this mapping is a powerful and unusual capability of this MVC framework. For example, it is possible to write a custom mapping based on session state, cookie state or many other variables. No other MVC framework seems to be equally flexible.
Note: Implementations can implement the Ordered
interface to be able to specify a sorting order and thus a priority for getting
applied by DispatcherServlet. Non-Ordered instances get treated as lowest priority.
Ordered
,
AbstractHandlerMapping
,
BeanNameUrlHandlerMapping
,
SimpleUrlHandlerMapping
Field Summary | |
---|---|
static String |
PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE
Name of the HttpServletRequest attribute that contains the path
within the handler mapping, in case of a pattern match, or the full
relevant URI (typically within the DispatcherServlet's mapping) else. |
Method Summary | |
---|---|
HandlerExecutionChain |
getHandler(HttpServletRequest request)
Return a handler and any interceptors for this request. |
Field Detail |
---|
static final String PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE
HttpServletRequest
attribute that contains the path
within the handler mapping, in case of a pattern match, or the full
relevant URI (typically within the DispatcherServlet's mapping) else.
Note: This attribute is not required to be supported by all HandlerMapping implementations. URL-based HandlerMappings will typically support it, but handlers should not necessarily expect this request attribute to be present in all scenarios.
Method Detail |
---|
HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception
The returned HandlerExecutionChain contains a handler Object, rather than even a tag interface, so that handlers are not constrained in any way. For example, a HandlerAdapter could be written to allow another framework's handler objects to be used.
Returns null
if no match was found. This is not an error.
The DispatcherServlet will query all registered HandlerMapping beans to find
a match, and only decide there is an error if none can find a handler.
request
- current HTTP request
null
if no mapping found
Exception
- if there is an internal error
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