- All Known Subinterfaces:
TypeBasedGuardingDynamicLinker
- All Known Implementing Classes:
BeansLinker
,CompositeGuardingDynamicLinker
,CompositeTypeBasedGuardingDynamicLinker
public interface GuardingDynamicLinker
The base interface for language-specific dynamic linkers. Such linkers
always have to produce method handles with guards, as the validity of the
method handle for calls at a call site inevitably depends on some condition
(at the very least, it depends on the receiver belonging to the language
runtime of the linker). Language runtime implementors will normally implement
the linking logic for their own language as one or more
GuardingDynamicLinker
classes. They will typically set them as
prioritized linkers
in the DynamicLinkerFactory
they configure for themselves, and maybe also
set some as fallback
linkers
to handle language-specific "property not found" etc. conditions.
Consider implementing TypeBasedGuardingDynamicLinker
interface
instead of this interface for those linkers that are based on the Java class
of the objects. If you need to implement language-specific type conversions,
have your GuardingDynamicLinker
also implement the
GuardingTypeConverterFactory
interface.
Languages can export linkers to other language runtimes for
automatic discovery
using a GuardingDynamicLinkerExporter
.
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Method Summary
Modifier and TypeMethodDescriptiongetGuardedInvocation
(LinkRequest linkRequest, LinkerServices linkerServices) Creates a guarded invocation appropriate for a particular invocation with the specified arguments at a call site.
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Method Details
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getGuardedInvocation
GuardedInvocation getGuardedInvocation(LinkRequest linkRequest, LinkerServices linkerServices) throws Exception Creates a guarded invocation appropriate for a particular invocation with the specified arguments at a call site.- Parameters:
linkRequest
- the object describing the request for linking a particular invocationlinkerServices
- linker services- Returns:
- a guarded invocation with a method handle suitable for the
arguments, as well as a guard condition that if fails should trigger
relinking. Must return null if it can't resolve the invocation. If the
returned invocation is unconditional (which is actually quite rare), the
guard in the return value can be null. The invocation can also have any
number of switch points for asynchronous invalidation of the linkage, as
well as a
Throwable
subclass that describes an expected exception condition that also triggers relinking (often it is faster to rely on an infrequent but expectedClassCastException
than on an always evaluatedinstanceof
guard). While the linker must produce an invocation with parameter types matching those in the call site descriptor of the link request, it should not try to match the return type expected at the call site except when it can do it with only the conversions that lose neither precision nor magnitude, seeLinkerServices.asTypeLosslessReturn(MethodHandle, MethodType)
for further explanation. - Throws:
Exception
- if the operation fails for whatever reason
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