de.alpharogroup.lang

Class TypeArgumentsExtensions

java.lang.Object

de.alpharogroup.lang.TypeArgumentsExtensions

public final class TypeArgumentsExtensions
extends Object

The class TypeArgumentsExtensions is a utility class for getting the type arguments from a child class that extended a generic base class.

It is inspired from the article Reflecting generics by Ian Robertson at http://www.artima.com/weblogs/viewpost.jsp?thread=208860.

In the comments someone asked if we are allowed to use the source code from the article. The answer of Ian Robertson is: Absolutely, you may use this code. "Consider it open sourced".

Constructor Summary

Constructors

Constructor and Description
TypeArgumentsExtensions()

Method Summary

Modifier and Type	Method and Description
static Class<?>	getClass(Type type) Get the underlying class for a type, or null if the type is a variable type.
static <T> Class<?>	getFirstTypeArgument(Class<? extends T> childClass) Gets the first type argument from the childClass.
static <T> Class<?>	getFirstTypeArgument(Class<T> baseClass, Class<? extends T> childClass) Gets the first type argument from the childClass.
static <T> Class<?>	getTypeArgument(Class<? extends T> childClass, int index) Gets the type argument from the childClass at the given index or null if it does not exists.
static <T> Class<?>	getTypeArgument(Class<T> baseClass, Class<? extends T> childClass, int index) Gets the type argument from the childClass at the given index or null if it does not exists.
static <T> List<Class<?>>	getTypeArguments(Class<? extends T> childClass) Get the actual type arguments from the given child class.
static <T> List<Class<?>>	getTypeArguments(Class<T> baseClass, Class<? extends T> childClass) Get the actual type arguments a child class has used to extend a generic base class.
static Map<Type,Type>	getTypeArgumentsAndParameters(ParameterizedType parameterizedType) Gets the type arguments and parameters.

Methods inherited from class java.lang.Object

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

Constructor Detail

TypeArgumentsExtensions

public TypeArgumentsExtensions()

Method Detail

getClass

public static Class<?> getClass(@NonNull
                                Type type)

Get the underlying class for a type, or null if the type is a variable type.

Parameters:

type - the type

Returns:

the underlying class

getFirstTypeArgument

public static <T> Class<?> getFirstTypeArgument(@NonNull
                                                Class<? extends T> childClass)

Gets the first type argument from the childClass. The base class will be resolved.

Type Parameters:

T - the generic type of the baseClass

Parameters:

childClass - the child class

Returns:

the first type argument

getFirstTypeArgument

public static <T> Class<?> getFirstTypeArgument(@NonNull
                                                Class<T> baseClass,
                                                @NonNull
                                                Class<? extends T> childClass)

Gets the first type argument from the childClass.

Type Parameters:

T - the generic type of the baseClass

Parameters:

baseClass - the base class

childClass - the child class

Returns:

the first type argument

getTypeArgument

public static <T> Class<?> getTypeArgument(@NonNull
                                           Class<? extends T> childClass,
                                           int index)

Gets the type argument from the childClass at the given index or null if it does not exists. The base class will be resolved.

Type Parameters:

T - the generic type of the baseClass

Parameters:

childClass - the child class

index - the index of the type argument

Returns:

the type argument from the childClass at the given index or null if it does not exists.

getTypeArgument

public static <T> Class<?> getTypeArgument(@NonNull
                                           Class<T> baseClass,
                                           @NonNull
                                           Class<? extends T> childClass,
                                           int index)

Gets the type argument from the childClass at the given index or null if it does not exists.

Type Parameters:

T - the generic type of the baseClass

Parameters:

baseClass - the base class

childClass - the child class

index - the index of the type argument

Returns:

the type argument from the childClass at the given index or null if it does not exists.

getTypeArguments

public static <T> List<Class<?>> getTypeArguments(@NonNull
                                                  Class<? extends T> childClass)

Get the actual type arguments from the given child class.

Type Parameters:

T - the generic type of the baseClass

Parameters:

childClass - the child class

Returns:

a list of the raw classes for the actual type arguments.

getTypeArguments

public static <T> List<Class<?>> getTypeArguments(@NonNull
                                                  Class<T> baseClass,
                                                  @NonNull
                                                  Class<? extends T> childClass)

Get the actual type arguments a child class has used to extend a generic base class.

Type Parameters:

T - the generic type of the baseClass

Parameters:

baseClass - the base class

childClass - the child class

Returns:

a list of the raw classes for the actual type arguments.

getTypeArgumentsAndParameters

public static Map<Type,Type> getTypeArgumentsAndParameters(@NonNull
                                                           ParameterizedType parameterizedType)

Gets the type arguments and parameters.

Parameters:

parameterizedType - the parameterized type

Returns:

the type arguments and parameters