- Functional Interface:
- This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
A factory for creating method handles for linking missing member behavior
in
BeansLinker
. BeansLinker links these method handles into guarded
invocations for link requests specifying GET_*
and SET_*
StandardOperation
s when it is either certain or possible that the
requested member (property, method, or element) is missing. They will be
linked both for named
and unnamed operations. The
implementer must ensure that the parameter types of the returned method
handle match the parameter types of the call site described in the link
request. The return types can differ, though, to allow
DynamicLinkerFactory.setPrelinkTransformer(jdk.dynalink.linker.GuardedInvocationTransformer)
late return type transformations}. It is allowed to return null
for a
method handle if the default behavior is sufficient.
Default missing member behavior
When aBeansLinker
is configured without a missing member handler
factory, or the factory returns null
for a particular handler
creation invocation, the default behavior is used. The default behavior is to
return null
from
BeansLinker.getGuardedInvocation(LinkRequest, LinkerServices)
when it
can be determined at link time that the linked operation will never address
an existing member. This lets the DynamicLinker
attempt the next
linker if there is one, or ultimately fail the link request with
NoSuchDynamicMethodException
. For other cases (typically all unnamed
member operations as well as most named operations on collection elements)
BeansLinker
will produce a conditional linkage that will return
null
when invoked at runtime with a name that does not match any
member for getters and silently ignore the passed values for setters.
Implementing exception-throwing behavior
Note that if the language-specific behavior for an operation on a missing member is to throw an exception then the factory should produce a method handle that throws the exception when invoked, and must not throw an exception itself, as the linkage for the missing member is often conditional.- See Also:
-
Method Summary
Modifier and TypeMethodDescriptioncreateMissingMemberHandler
(LinkRequest linkRequest, LinkerServices linkerServices) Returns a method handle suitable for implementing missing member behavior for a particular link request.
-
Method Details
-
createMissingMemberHandler
MethodHandle createMissingMemberHandler(LinkRequest linkRequest, LinkerServices linkerServices) throws Exception Returns a method handle suitable for implementing missing member behavior for a particular link request. See the class description for details.- Parameters:
linkRequest
- the current link requestlinkerServices
- the current link services- Returns:
- a method handle that can be invoked if the property, element, or method being addressed by an operation is missing. The return value can be null.
- Throws:
Exception
- if the operation fails for any reason. Please observe the class documentation notes for implementing exception-throwing missing member behavior.
-