ch.jalu.injector

Interface Injector

All Known Implementing Classes:

InjectorImpl

public interface Injector

Dependency injector.

Allows you to retrieve singletons and create new instances. By default, it supports field and constructor injection and executes methods annotated with @PostConstruct. You can obtain an injector and customize its behavior with the InjectorBuilder.

Method Summary

Modifier and Type	Method and Description
<T> T	createIfHasDependencies(Class<T> clazz) Creates an instance of the given class if all of its dependencies are available.
<T> T	getIfAvailable(Class<T> clazz) Returns the singleton of the given class if available.
<T> T	getSingleton(Class<T> clazz) Retrieves or instantiates an object of the given type (singleton scope).
<T> T	newInstance(Class<T> clazz) Request-scoped method to instantiate a new object of the given class.
void	provide(Class<? extends Annotation> annotation, Object object) Processes an annotation with an associated object.
<T> void	register(Class<? super T> clazz, T object) Registers an object as the singleton of the given class.
<T,P extends javax.inject.Provider<? extends T>> void	registerProvider(Class<T> clazz, Class<P> providerClass) Registers the provider class to instantiate a given class.
<T> void	registerProvider(Class<T> clazz, javax.inject.Provider<? extends T> provider) Registers a provider for the given class.
<T> Collection<T>	retrieveAllOfType(Class<T> clazz) Returns all known singletons of the given type.

Method Detail

register

<T> void register(Class<? super T> clazz,
                  T object)

Registers an object as the singleton of the given class. Throws an exception if a singleton is already available for the class.

Type Parameters:

T - the type to register the object for

Parameters:

clazz - the class to register the object for

object - the object

Since:

0.1

registerProvider

<T> void registerProvider(Class<T> clazz,
                          javax.inject.Provider<? extends T> provider)

Registers a provider for the given class. The provider is used whenever the class needs to be instantiated.

Type Parameters:

T - the class' type

Parameters:

clazz - the class to register the provider for

provider - the provider

Since:

0.3

registerProvider

<T,P extends javax.inject.Provider<? extends T>> void registerProvider(Class<T> clazz,
                                                                       Class<P> providerClass)

Registers the provider class to instantiate a given class. The first time the clazz has to be instantiated, the providerClass will be instantiated.

Type Parameters:

T - the class' type

P - the provider's type

Parameters:

clazz - the class to register the provider for

providerClass - the class of the provider

Since:

0.3

provide

void provide(Class<? extends Annotation> annotation,
             @Nullable
             Object object)

Processes an annotation with an associated object. The actual behavior of this method depends on the configured handlers of the injector. By default it register the given object for the annotation such that it may be later injected with the annotation as identifier.

Parameters:

annotation - the annotation

object - the object

Since:

0.1

getSingleton

<T> T getSingleton(Class<T> clazz)

Retrieves or instantiates an object of the given type (singleton scope).

Type Parameters:

T - the class' type

Parameters:

clazz - the class to retrieve the value for

Returns:

object of the class' type

Since:

0.1

newInstance

<T> T newInstance(Class<T> clazz)

Request-scoped method to instantiate a new object of the given class. The injector does not keep track of it afterwards; it will always return a new instance and forget about it.

Type Parameters:

T - the class' type

Parameters:

clazz - the class to instantiate

Returns:

new instance of class T

Since:

0.1

getIfAvailable

@Nullable
<T> T getIfAvailable(Class<T> clazz)

Returns the singleton of the given class if available. This simply returns the instance if present, and otherwise null. Calling this method will never create any new objects.

Type Parameters:

T - the class' type

Parameters:

clazz - the class to retrieve the instance for

Returns:

instance or null if not available

Since:

0.1

createIfHasDependencies

@Nullable
<T> T createIfHasDependencies(Class<T> clazz)

Creates an instance of the given class if all of its dependencies are available. A new instance is returned each time and the created object is not stored in the injector.

Note: Currently, all dependencies of the class need to be registered singletons for a new instance to be created. This limitation may be lifted in future versions.

Type Parameters:

T - the class' type

Parameters:

clazz - the class to construct if possible

Returns:

instance of the class, or null if any dependency does not already exist

retrieveAllOfType

<T> Collection<T> retrieveAllOfType(Class<T> clazz)

Returns all known singletons of the given type. Typically used with interfaces in order to perform an action without knowing its concrete implementors. Trivially, using Object as clazz will return all known singletons.

Type Parameters:

T - the class' type

Parameters:

clazz - the class to retrieve singletons of

Returns:

list of singletons of the given type

Since:

0.1