Module com.google.gson
Package com.google.gson.reflect

Class TypeToken<T>

java.lang.Object
com.google.gson.reflect.TypeToken<T>
public class TypeToken<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 the type information even at runtime.

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

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

Capturing a type variable as type argument of a TypeToken should be avoided. Due to type erasure the runtime type of a type variable is not available to Gson and therefore it cannot provide the functionality one might expect, which gives a false sense of type-safety at compilation time and can lead to an unexpected ClassCastException at runtime.

If the type arguments of the parameterized type are only available at runtime, for example when you want to create a List<E> based on a Class<E> representing the element type, the method getParameterized(Type, Type...) can be used.

Author:
Bob Lee, Sven Mawson, Jesse Wilson

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    TypeToken()
    Constructs a new type literal.

  • Method Summary

    Modifier and Type
    Method
    Description
    final boolean
    equals(Object o)
     
    static <T> TypeToken<T>
    get(Class<T> type)
    Gets type literal for the given Class instance.
    static TypeToken<?>
    get(Type type)
    Gets type literal for the given Type instance.
    static TypeToken<?>
    getArray(Type componentType)
    Gets type literal for the array type whose elements are all instances of componentType.
    static TypeToken<?>
    getParameterized(Type rawType, Type... typeArguments)
    Gets a type literal for the parameterized type represented by applying typeArguments to rawType.
    final Class<? super T>
    getRawType()
    Returns the raw (non-generic) type for this type.
    final Type
    getType()
    Gets underlying Type instance.
    final int
    hashCode()
     
    boolean
    isAssignableFrom(TypeToken<?> token)
    Deprecated.
    this implementation may be inconsistent with javac for types with wildcards.
    boolean
    isAssignableFrom(Class<?> cls)
    Deprecated.
    this implementation may be inconsistent with javac for types with wildcards.
    boolean
    isAssignableFrom(Type from)
    Deprecated.
    this implementation may be inconsistent with javac for types with wildcards.
    final String
    toString()
     

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • TypeToken

      protected TypeToken()
      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 Details

    • getRawType

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

    • getType

      public final Type getType()
      Gets underlying Type instance.

    • isAssignableFrom

      @Deprecated public boolean isAssignableFrom(Class<?> cls)
      Deprecated.
      this implementation may be inconsistent with javac for types with wildcards.
      Check if this type is assignable from the given class object.

    • isAssignableFrom

      @Deprecated public boolean isAssignableFrom(Type from)
      Deprecated.
      this implementation may be inconsistent with javac for types with wildcards.
      Check if this type is assignable from the given Type.

    • isAssignableFrom

      @Deprecated public boolean isAssignableFrom(TypeToken<?> token)
      Deprecated.
      this implementation may be inconsistent with javac for types with wildcards.
      Check if this type is assignable from the given type token.

    • hashCode

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

    • equals

      public final boolean equals(Object o)
      Overrides:
      equals in class Object

    • toString

      public final String toString()
      Overrides:
      toString in class Object

    • get

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

    • get

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

    • getParameterized

      public static TypeToken<?> getParameterized(Type rawType, Type... typeArguments)
      Gets a type literal for the parameterized type represented by applying typeArguments to rawType. This is mainly intended for situations where the type arguments are not available at compile time. The following example shows how a type token for Map<K, V> can be created: 
      
 Class<K> keyClass = ...;
 Class<V> valueClass = ...;
 TypeToken<?> mapTypeToken = TypeToken.getParameterized(Map.class, keyClass, valueClass);
      As seen here the result is a TypeToken<?>; this method cannot provide any type safety, and care must be taken to pass in the correct number of type arguments.
      Throws:
      IllegalArgumentException - If rawType is not of type Class, or if the type arguments are invalid for the raw type

    • getArray

      public static TypeToken<?> getArray(Type componentType)
      Gets type literal for the array type whose elements are all instances of componentType.