org.grouplens.grapht

Interface Injector

All Superinterfaces:

AutoCloseable

All Known Implementing Classes:

DefaultInjector

public interface Injector
extends AutoCloseable

Injector uses dependency injection to act as a factory for creating instances with complex dependencies. A default implementation of Injector can easily be created by using an InjectorBuilder:

 InjectorBuilder b = new InjectorBuilder();
 b.bind(Foo.class).to(Bar.class);
 b.applyModule(new MyCustomModule());
 // other bindings
 Injector i = b.build();
 assert (i.getInstance(Foo.class) instanceof Bar);
 

Alternatively, BindingFunctionBuilder and DependencySolver can be used to create your own Injector implementations.

Author:

GroupLens Research

Method Summary

Modifier and Type	Method and Description
void	close() Close the injector, shutting down any instantiated components that require shutdown.
<T> T	getInstance(Annotation qualifier, Class<T> type) Get an instance of T with the given Qualifier annotation.
<T> T	getInstance(Class<T> type) Get an instance of T based on the bindings that this Injector was configured with.
<T> T	tryGetInstance(Annotation qualifier, Class<T> type) Try to get an instance of a component, returning null if the component does not have a configured implementation.

Method Detail

getInstance

@Nonnull
<T> T getInstance(Class<T> type)
                     throws InjectionException

Get an instance of T based on the bindings that this Injector was configured with. An exception is thrown if the request type cannot be instantiated with dependency injection.

Injectors may memoize or cache previously created objects. As an example, the Injector created by InjectorBuilder reuses instances where possible.

Type Parameters:

T - The object type being created

Parameters:

type - The class type

Returns:

An instance of type T

Throws:

ConstructionException - if type cannot be instantiated

InjectionException

getInstance

@Nonnull
<T> T getInstance(Annotation qualifier,
                            Class<T> type)
                     throws InjectionException

Get an instance of T with the given Qualifier annotation.

Type Parameters:

T - The object type

Parameters:

qualifier - The qualifier on of the returned instance

type - The class type

Returns:

An instance of type T

Throws:

ConstructionException - if type cannot be instantiated

InjectionException

tryGetInstance

@Nullable
<T> T tryGetInstance(Annotation qualifier,
                                Class<T> type)
                         throws InjectionException

Try to get an instance of a component, returning null if the component does not have a configured implementation.

Type Parameters:

T - The component type.

Parameters:

qualifier - The qualifier, or null for an unqualified component.

type - The component type.

Returns:

An instance of type T, or null if no implemenation of T is configured.

Throws:

InjectionException - if there is some other error injecting the instance.

close

void close()

Close the injector, shutting down any instantiated components that require shutdown.

Specified by:

close in interface AutoCloseable