Package com.google.inject

Class Key<T>

  • public class Key<T>
extends Object
    Guice uses Key objects to identify a dependency that can be resolved by the Guice Injector. A Guice key consists of an injection type and an optional annotation.

    For example, Key.get(Service.class, Transactional.class) will match: 

       @Inject
   public void setService(@Transactional Service service) {
     ...
   }

    Key supports generic types via subclassing just like TypeLiteral.

    Keys do not differentiate between primitive types (int, char, etc.) and their corresponding wrapper types (Integer, Character, etc.). Primitive types will be replaced with their wrapper types when keys are created.

    • Constructor Detail

      • Key

        protected Key​(Class<? extends Annotation> annotationType)
        Constructs a new key. Derives the type from this class's type parameter.

        Clients create an empty anonymous subclass. Doing so embeds the type parameter in the anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.

        Example usage for a binding of type Foo annotated with @Bar:

        new Key<Foo>(Bar.class) {}.

      • Key

        protected Key​(Annotation annotation)
        Constructs a new key. Derives the type from this class's type parameter.

        Clients create an empty anonymous subclass. Doing so embeds the type parameter in the anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.

        Example usage for a binding of type Foo annotated with @Bar:

        new Key<Foo>(new Bar()) {}.

      • Key

        protected Key()
        Constructs a new key. Derives the type from this class's type parameter.

        Clients create an empty anonymous subclass. Doing so embeds the type parameter in the anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.

        Example usage for a binding of type Foo:

        new Key<Foo>() {}.

    • Method Detail

      • getTypeLiteral

        public final TypeLiteral<T> getTypeLiteral()
        Gets the key type.

      • getAnnotationType

        public final Class<? extends Annotation> getAnnotationType()
        Gets the annotation type. Will be null if this key lacks an annotation.

      • getAnnotation

        public final Annotation getAnnotation()
        Gets the annotation instance if available. Will be null if this key lacks an annotation or the key was constructed with a Class<Annotation>.

        Warning: this can return null even if this key is annotated. To check whether a Key has an annotation use hasAnnotationType() instead.

      • hashCode

        public final int hashCode()
        Overrides:
        hashCode in class Object

      • get

        public static <T> Key<T> get​(Class<T> type)
        Gets a key for an injection type.

      • get

        public static <T> Key<T> get​(Class<T> type,
                             Class<? extends Annotation> annotationType)
        Gets a key for an injection type and an annotation type.

      • get

        public static <T> Key<T> get​(Class<T> type,
                             Annotation annotation)
        Gets a key for an injection type and an annotation.

      • get

        public static Key<?> get​(Type type)
        Gets a key for an injection type.

      • get

        public static Key<?> get​(Type type,
                         Class<? extends Annotation> annotationType)
        Gets a key for an injection type and an annotation type.

      • get

        public static Key<?> get​(Type type,
                         Annotation annotation)
        Gets a key for an injection type and an annotation.

      • get

        public static <T> Key<T> get​(TypeLiteral<T> typeLiteral)
        Gets a key for an injection type.

      • get

        public static <T> Key<T> get​(TypeLiteral<T> typeLiteral,
                             Class<? extends Annotation> annotationType)
        Gets a key for an injection type and an annotation type.

      • get

        public static <T> Key<T> get​(TypeLiteral<T> typeLiteral,
                             Annotation annotation)
        Gets a key for an injection type and an annotation.

      • ofType

        public <U> Key<U> ofType​(Class<U> type)
        Returns a new key of the specified type with the same annotation as this key.
        Since:
        3.0

      • ofType

        public Key<?> ofType​(Type type)
        Returns a new key of the specified type with the same annotation as this key.
        Since:
        3.0

      • ofType

        public <U> Key<U> ofType​(TypeLiteral<U> type)
        Returns a new key of the specified type with the same annotation as this key.
        Since:
        3.0

      • withAnnotation

        public Key<T> withAnnotation​(Class<? extends Annotation> annotationType)
        Returns a new key of the same type with the specified annotation.

        This is equivalent to Key.get(key.getTypeLiteral(), annotation) but may be more convenient to use in certain cases.

        Since:
        5.0

      • withAnnotation

        public Key<T> withAnnotation​(Annotation annotation)
        Returns a new key of the same type with the specified annotation.

        This is equivalent to Key.get(key.getTypeLiteral(), annotation) but may be more convenient to use in certain cases.

        Since:
        5.0

      • hasAttributes

        public boolean hasAttributes()
        Returns true if this key has annotation attributes.
        Since:
        3.0

      • withoutAttributes

        public Key<T> withoutAttributes()
        Returns this key without annotation attributes, i.e. with only the annotation type.
        Since:
        3.0