Interface MasterObjectProvider
- All Known Implementing Classes:
MasterObjectProviderImpl
A service that acts as a chain-of-command over a number of
ObjectProvider
, but
allows for the case where no object may be provided.
This service is itself a key part of Tapestry's general injection mechanism; it is used when instantiating a service
implementation instance, invoking module methods (service builder, decorator, or contribution methods), when
autobuilding objects of any type.
As of Tapestry 5.3, the MasterObjectProvider allows injection of OperationTracker
as a
special case (not based on a contributed ObjectProvider).-
Method Summary
Modifier and TypeMethodDescription<T> T
provide
(Class<T> objectType, AnnotationProvider annotationProvider, ObjectLocator locator, boolean required) Provides an object based on an expression.
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Method Details
-
provide
<T> T provide(Class<T> objectType, AnnotationProvider annotationProvider, ObjectLocator locator, boolean required) Provides an object based on an expression. The process of providing objects occurs within a particular context, which will typically be a service builder method, service contributor method, or service decorator method. The locator parameter provides access to the services visible to that context. When the value is required and noObjectProvider
provided a non-null value, thenObjectLocator.getService(Class, Class[])
is invoked (with no marker annotations), to provide a uniquely matching service, or throw a failure exception if no single service can be found.- Type Parameters:
T
-- Parameters:
objectType
- the expected object typeannotationProvider
- provides access to annotations (typically, the field or parameter to which an injection-related annotation is attached); annotations on the field or parameter may also be used when resolving the desired objectlocator
- locator for the context in which the provider is being usedrequired
- if true (normal case) a value must be provided; if false then it is allowed for no ObjectProvider to provide a value, and this method may return null to indicate the failure- Returns:
- the requested object, or null if this object provider can not supply an object
- Throws:
RuntimeException
- if the expression can not be evaluated, or the type of object identified is not assignable to the type specified by the objectType parameter
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