com.google.inject

Class TypeLiteral<T>


  • public class TypeLiteral<T>
extends Object
    Represents a generic type T. Java doesn't yet provide a way to represent generic types, so this class does. Forces clients to create a subclass of this class which enables retrieval of the type information even at runtime.

    For example, to create a type literal for List<String>, you can create an empty anonymous inner class:

    TypeLiteral<List<String>> list = new TypeLiteral<List<String>>() {};

    Along with modeling generic types, this class can resolve type parameters. For example, to figure out what type keySet() returns on a Map<Integer, String>, use this code: 

    TypeLiteral<Map<Integer, String>> mapType
     = new TypeLiteral<Map<Integer, String>>() {};
 TypeLiteral<?> keySetType
     = mapType.getReturnType(Map.class.getMethod("keySet"));
 System.out.println(keySetType); // prints "Set<Integer>"

    Author:
    crazybob@google.com (Bob Lee), jessewilson@google.com (Jesse Wilson)

    • Constructor Detail

      • TypeLiteral

        protected TypeLiteral()
        Constructs a new type literal. Derives represented class from 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.

    • Method Detail

      • getRawType

        public final Class<? super T> getRawType()
        Returns the raw (non-generic) type for this type.
        Since:
        2.0

      • getType

        public final Type getType()
        Gets underlying Type instance.

      • hashCode

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

      • get

        public static TypeLiteral<?> get(Type type)
        Gets type literal for the given Type instance.

      • get

        public static <T> TypeLiteral<T> get(Class<T> type)
        Gets type literal for the given Class instance.

      • getSupertype

        public TypeLiteral<?> getSupertype(Class<?> supertype)
        Returns the generic form of supertype. For example, if this is ArrayList<String>, this returns Iterable<String> given the input Iterable.class.
        Parameters:
        supertype - a superclass of, or interface implemented by, this.
        Since:
        2.0

      • getFieldType

        public TypeLiteral<?> getFieldType(Field field)
        Returns the resolved generic type of field.
        Parameters:
        field - a field defined by this or any superclass.
        Since:
        2.0

      • getParameterTypes

        public List<TypeLiteral<?>> getParameterTypes(Member methodOrConstructor)
        Returns the resolved generic parameter types of methodOrConstructor.
        Parameters:
        methodOrConstructor - a method or constructor defined by this or any supertype.
        Since:
        2.0

      • getExceptionTypes

        public List<TypeLiteral<?>> getExceptionTypes(Member methodOrConstructor)
        Returns the resolved generic exception types thrown by constructor.
        Parameters:
        methodOrConstructor - a method or constructor defined by this or any supertype.
        Since:
        2.0

      • getReturnType

        public TypeLiteral<?> getReturnType(Method method)
        Returns the resolved generic return type of method.
        Parameters:
        method - a method defined by this or any supertype.
        Since:
        2.0

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