Package org.apache.commons.lang3.reflect

Class TypeUtils

  • public class TypeUtils
extends java.lang.Object

    Utility methods focusing on type inspection, particularly with regard to generics.

    Since:
    3.0

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.lang.reflect.WildcardType WILDCARD_ALL
      A wildcard instance matching ?.

    • Constructor Summary

      Constructors 
      Constructor Description
      TypeUtils()
      TypeUtils instances should NOT be constructed in standard programming.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static boolean containsTypeVariables​(java.lang.reflect.Type type)
      Learn, recursively, whether any of the type parameters associated with type are bound to variables.
      static java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> determineTypeArguments​(java.lang.Class<?> cls, java.lang.reflect.ParameterizedType superType)
      Tries to determine the type arguments of a class/interface based on a super parameterized type's type arguments.
      static boolean equals​(java.lang.reflect.Type type1, java.lang.reflect.Type type2)
      Check equality of types.
      static java.lang.reflect.GenericArrayType genericArrayType​(java.lang.reflect.Type componentType)
      Create a generic array type instance.
      static java.lang.reflect.Type getArrayComponentType​(java.lang.reflect.Type type)
      Gets the array component type of type.
      static java.lang.reflect.Type[] getImplicitBounds​(java.lang.reflect.TypeVariable<?> typeVariable)
      Returns an array containing the sole type of Object if TypeVariable.getBounds() returns an empty array.
      static java.lang.reflect.Type[] getImplicitLowerBounds​(java.lang.reflect.WildcardType wildcardType)
      Returns an array containing a single value of null if WildcardType.getLowerBounds() returns an empty array.
      static java.lang.reflect.Type[] getImplicitUpperBounds​(java.lang.reflect.WildcardType wildcardType)
      Returns an array containing the sole value of Object if WildcardType.getUpperBounds() returns an empty array.
      static java.lang.Class<?> getRawType​(java.lang.reflect.Type type, java.lang.reflect.Type assigningType)
      Get the raw type of a Java type, given its context.
      static java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> getTypeArguments​(java.lang.reflect.ParameterizedType type)
      Retrieves all the type arguments for this parameterized type including owner hierarchy arguments such as Outer<K, V>.Inner<T>.DeepInner<E> .
      static java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> getTypeArguments​(java.lang.reflect.Type type, java.lang.Class<?> toClass)
      Gets the type arguments of a class/interface based on a subtype.
      static boolean isArrayType​(java.lang.reflect.Type type)
      Learn whether the specified type denotes an array type.
      static boolean isAssignable​(java.lang.reflect.Type type, java.lang.reflect.Type toType)
      Checks if the subject type may be implicitly cast to the target type following the Java generics rules.
      static boolean isInstance​(java.lang.Object value, java.lang.reflect.Type type)
      Checks if the given value can be assigned to the target type following the Java generics rules.
      static java.lang.reflect.Type[] normalizeUpperBounds​(java.lang.reflect.Type[] bounds)
      This method strips out the redundant upper bound types in type variable types and wildcard types (or it would with wildcard types if multiple upper bounds were allowed).
      static java.lang.reflect.ParameterizedType parameterize​(java.lang.Class<?> rawClass, java.lang.reflect.Type... typeArguments)
      Create a parameterized type instance.
      static java.lang.reflect.ParameterizedType parameterize​(java.lang.Class<?> rawClass, java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeArgMappings)
      Create a parameterized type instance.
      static java.lang.reflect.ParameterizedType parameterizeWithOwner​(java.lang.reflect.Type owner, java.lang.Class<?> rawClass, java.lang.reflect.Type... typeArguments)
      Create a parameterized type instance.
      static java.lang.reflect.ParameterizedType parameterizeWithOwner​(java.lang.reflect.Type owner, java.lang.Class<?> rawClass, java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeArgMappings)
      Create a parameterized type instance.
      static java.lang.String toLongString​(java.lang.reflect.TypeVariable<?> var)
      Format a TypeVariable including its GenericDeclaration.
      static java.lang.String toString​(java.lang.reflect.Type type)
      Present a given type as a Java-esque String.
      static boolean typesSatisfyVariables​(java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeVarAssigns)
      Determines whether or not specified types satisfy the bounds of their mapped type variables.
      static java.lang.reflect.Type unrollVariables​(java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeArguments, java.lang.reflect.Type type)
      Gets a type representing type with variable assignments "unrolled."
      static TypeUtils.WildcardTypeBuilder wildcardType()
      Gets a TypeUtils.WildcardTypeBuilder.
      static <T> Typed<T> wrap​(java.lang.Class<T> type)
      Wrap the specified Class in a Typed wrapper.
      static <T> Typed<T> wrap​(java.lang.reflect.Type type)
      Wrap the specified Type in a Typed wrapper.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • WILDCARD_ALL

        public static final java.lang.reflect.WildcardType WILDCARD_ALL
        A wildcard instance matching ?.
        Since:
        3.2

    • Constructor Detail

      • TypeUtils

        public TypeUtils()

        TypeUtils instances should NOT be constructed in standard programming. Instead, the class should be used as TypeUtils.isAssignable(cls, toClass).

        This constructor is public to permit tools that require a JavaBean instance to operate.

    • Method Detail

      • isAssignable

        public static boolean isAssignable​(java.lang.reflect.Type type,
                                   java.lang.reflect.Type toType)

        Checks if the subject type may be implicitly cast to the target type following the Java generics rules. If both types are Class objects, the method returns the result of ClassUtils.isAssignable(Class, Class).

        Parameters:
        type - the subject type to be assigned to the target type
        toType - the target type
        Returns:
        true if type is assignable to toType.

      • getTypeArguments

        public static java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> getTypeArguments​(java.lang.reflect.ParameterizedType type)

        Retrieves all the type arguments for this parameterized type including owner hierarchy arguments such as Outer<K, V>.Inner<T>.DeepInner<E> . The arguments are returned in a Map specifying the argument type for each TypeVariable.

        Parameters:
        type - specifies the subject parameterized type from which to harvest the parameters.
        Returns:
        a Map of the type arguments to their respective type variables.

      • getTypeArguments

        public static java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> getTypeArguments​(java.lang.reflect.Type type,
                                                                                                             java.lang.Class<?> toClass)

        Gets the type arguments of a class/interface based on a subtype. For instance, this method will determine that both of the parameters for the interface Map are Object for the subtype Properties even though the subtype does not directly implement the Map interface.

        This method returns null if type is not assignable to toClass. It returns an empty map if none of the classes or interfaces in its inheritance hierarchy specify any type arguments.

        A side effect of this method is that it also retrieves the type arguments for the classes and interfaces that are part of the hierarchy between type and toClass. So with the above example, this method will also determine that the type arguments for Hashtable are also both Object. In cases where the interface specified by toClass is (indirectly) implemented more than once (e.g. where toClass specifies the interface Iterable and type specifies a parameterized type that implements both Set and Collection), this method will look at the inheritance hierarchy of only one of the implementations/subclasses; the first interface encountered that isn't a subinterface to one of the others in the type to toClass hierarchy.

        Parameters:
        type - the type from which to determine the type parameters of toClass
        toClass - the class whose type parameters are to be determined based on the subtype type
        Returns:
        a Map of the type assignments for the type variables in each type in the inheritance hierarchy from type to toClass inclusive.

      • determineTypeArguments

        public static java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> determineTypeArguments​(java.lang.Class<?> cls,
                                                                                                                   java.lang.reflect.ParameterizedType superType)

        Tries to determine the type arguments of a class/interface based on a super parameterized type's type arguments. This method is the inverse of getTypeArguments(Type, Class) which gets a class/interface's type arguments based on a subtype. It is far more limited in determining the type arguments for the subject class's type variables in that it can only determine those parameters that map from the subject Class object to the supertype.

        Example: TreeSet sets its parameter as the parameter for NavigableSet, which in turn sets the parameter of SortedSet, which in turn sets the parameter of Set, which in turn sets the parameter of Collection, which in turn sets the parameter of Iterable. Since TreeSet's parameter maps (indirectly) to Iterable's parameter, it will be able to determine that based on the super type Iterable<? extends Map<Integer, ? extends Collection<?>>>, the parameter of TreeSet is ? extends Map<Integer, ? extends Collection<?>>.

        Parameters:
        cls - the class whose type parameters are to be determined, not null
        superType - the super type from which cls's type arguments are to be determined, not null
        Returns:
        a Map of the type assignments that could be determined for the type variables in each type in the inheritance hierarchy from type to toClass inclusive.

      • isInstance

        public static boolean isInstance​(java.lang.Object value,
                                 java.lang.reflect.Type type)

        Checks if the given value can be assigned to the target type following the Java generics rules.

        Parameters:
        value - the value to be checked
        type - the target type
        Returns:
        true if value is an instance of type.

      • normalizeUpperBounds

        public static java.lang.reflect.Type[] normalizeUpperBounds​(java.lang.reflect.Type[] bounds)

        This method strips out the redundant upper bound types in type variable types and wildcard types (or it would with wildcard types if multiple upper bounds were allowed).

        Example, with the variable type declaration: 

        <K extends java.util.Collection<String> &
 java.util.List<String>>

        since List is a subinterface of Collection, this method will return the bounds as if the declaration had been: 

        <K extends java.util.List<String>>
        Parameters:
        bounds - an array of types representing the upper bounds of either WildcardType or TypeVariable, not null.
        Returns:
        an array containing the values from bounds minus the redundant types.

      • getImplicitBounds

        public static java.lang.reflect.Type[] getImplicitBounds​(java.lang.reflect.TypeVariable<?> typeVariable)

        Returns an array containing the sole type of Object if TypeVariable.getBounds() returns an empty array. Otherwise, it returns the result of TypeVariable.getBounds() passed into normalizeUpperBounds(java.lang.reflect.Type[]).

        Parameters:
        typeVariable - the subject type variable, not null
        Returns:
        a non-empty array containing the bounds of the type variable.

      • getImplicitUpperBounds

        public static java.lang.reflect.Type[] getImplicitUpperBounds​(java.lang.reflect.WildcardType wildcardType)

        Returns an array containing the sole value of Object if WildcardType.getUpperBounds() returns an empty array. Otherwise, it returns the result of WildcardType.getUpperBounds() passed into normalizeUpperBounds(java.lang.reflect.Type[]).

        Parameters:
        wildcardType - the subject wildcard type, not null
        Returns:
        a non-empty array containing the upper bounds of the wildcard type.

      • getImplicitLowerBounds

        public static java.lang.reflect.Type[] getImplicitLowerBounds​(java.lang.reflect.WildcardType wildcardType)

        Returns an array containing a single value of null if WildcardType.getLowerBounds() returns an empty array. Otherwise, it returns the result of WildcardType.getLowerBounds().

        Parameters:
        wildcardType - the subject wildcard type, not null
        Returns:
        a non-empty array containing the lower bounds of the wildcard type.

      • typesSatisfyVariables

        public static boolean typesSatisfyVariables​(java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeVarAssigns)

        Determines whether or not specified types satisfy the bounds of their mapped type variables. When a type parameter extends another (such as <T, S extends T>), uses another as a type parameter (such as <T, S extends Comparable>>), or otherwise depends on another type variable to be specified, the dependencies must be included in typeVarAssigns.

        Parameters:
        typeVarAssigns - specifies the potential types to be assigned to the type variables, not null.
        Returns:
        whether or not the types can be assigned to their respective type variables.

      • getRawType

        public static java.lang.Class<?> getRawType​(java.lang.reflect.Type type,
                                            java.lang.reflect.Type assigningType)

        Get the raw type of a Java type, given its context. Primarily for use with TypeVariables and GenericArrayTypes, or when you do not know the runtime type of type: if you know you have a Class instance, it is already raw; if you know you have a ParameterizedType, its raw type is only a method call away.

        Parameters:
        type - to resolve
        assigningType - type to be resolved against
        Returns:
        the resolved Class object or null if the type could not be resolved

      • isArrayType

        public static boolean isArrayType​(java.lang.reflect.Type type)
        Learn whether the specified type denotes an array type.
        Parameters:
        type - the type to be checked
        Returns:
        true if type is an array class or a GenericArrayType.

      • getArrayComponentType

        public static java.lang.reflect.Type getArrayComponentType​(java.lang.reflect.Type type)
        Gets the array component type of type.
        Parameters:
        type - the type to be checked
        Returns:
        component type or null if type is not an array type

      • unrollVariables

        public static java.lang.reflect.Type unrollVariables​(java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeArguments,
                                                     java.lang.reflect.Type type)
        Gets a type representing type with variable assignments "unrolled."
        Parameters:
        typeArguments - as from getTypeArguments(Type, Class)
        type - the type to unroll variable assignments for
        Returns:
        Type
        Since:
        3.2

      • containsTypeVariables

        public static boolean containsTypeVariables​(java.lang.reflect.Type type)
        Learn, recursively, whether any of the type parameters associated with type are bound to variables.
        Parameters:
        type - the type to check for type variables
        Returns:
        boolean
        Since:
        3.2

      • parameterize

        public static final java.lang.reflect.ParameterizedType parameterize​(java.lang.Class<?> rawClass,
                                                                     java.lang.reflect.Type... typeArguments)
        Create a parameterized type instance.
        Parameters:
        rawClass - the raw class to create a parameterized type instance for
        typeArguments - the types used for parameterization
        Returns:
        ParameterizedType
        Since:
        3.2

      • parameterize

        public static final java.lang.reflect.ParameterizedType parameterize​(java.lang.Class<?> rawClass,
                                                                     java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeArgMappings)
        Create a parameterized type instance.
        Parameters:
        rawClass - the raw class to create a parameterized type instance for
        typeArgMappings - the mapping used for parameterization
        Returns:
        ParameterizedType
        Since:
        3.2

      • parameterizeWithOwner

        public static final java.lang.reflect.ParameterizedType parameterizeWithOwner​(java.lang.reflect.Type owner,
                                                                              java.lang.Class<?> rawClass,
                                                                              java.lang.reflect.Type... typeArguments)
        Create a parameterized type instance.
        Parameters:
        owner - the owning type
        rawClass - the raw class to create a parameterized type instance for
        typeArguments - the types used for parameterization
        Returns:
        ParameterizedType
        Since:
        3.2

      • parameterizeWithOwner

        public static final java.lang.reflect.ParameterizedType parameterizeWithOwner​(java.lang.reflect.Type owner,
                                                                              java.lang.Class<?> rawClass,
                                                                              java.util.Map<java.lang.reflect.TypeVariable<?>,​java.lang.reflect.Type> typeArgMappings)
        Create a parameterized type instance.
        Parameters:
        owner - the owning type
        rawClass - the raw class to create a parameterized type instance for
        typeArgMappings - the mapping used for parameterization
        Returns:
        ParameterizedType
        Since:
        3.2

      • genericArrayType

        public static java.lang.reflect.GenericArrayType genericArrayType​(java.lang.reflect.Type componentType)
        Create a generic array type instance.
        Parameters:
        componentType - the type of the elements of the array. For example the component type of boolean[] is boolean
        Returns:
        GenericArrayType
        Since:
        3.2

      • equals

        public static boolean equals​(java.lang.reflect.Type type1,
                             java.lang.reflect.Type type2)
        Check equality of types.
        Parameters:
        type1 - the first type
        type2 - the second type
        Returns:
        boolean
        Since:
        3.2

      • toString

        public static java.lang.String toString​(java.lang.reflect.Type type)
        Present a given type as a Java-esque String.
        Parameters:
        type - the type to create a String representation for, not null
        Returns:
        String
        Since:
        3.2

      • toLongString

        public static java.lang.String toLongString​(java.lang.reflect.TypeVariable<?> var)
        Format a TypeVariable including its GenericDeclaration.
        Parameters:
        var - the type variable to create a String representation for, not null
        Returns:
        String
        Since:
        3.2

      • wrap

        public static <T> Typed<T> wrap​(java.lang.reflect.Type type)
        Wrap the specified Type in a Typed wrapper.
        Type Parameters:
        T - inferred generic type
        Parameters:
        type - to wrap
        Returns:
        Typed<T>
        Since:
        3.2

      • wrap

        public static <T> Typed<T> wrap​(java.lang.Class<T> type)
        Wrap the specified Class in a Typed wrapper.
        Type Parameters:
        T - generic type
        Parameters:
        type - to wrap
        Returns:
        Typed<T>
        Since:
        3.2