Package io.helidon.common

Class GenericType<T>

java.lang.Object

io.helidon.common.GenericType<T>

Type Parameters:

T - the generic type parameter

All Implemented Interfaces:

Type

public class GenericType<T>
extends Object
implements Type

Represents a full type including generics declaration, to avoid information loss due to type erasure. Supports in-line instantiation of objects that represent generic types with actual type parameters. An object that represents any parameterized type may be obtained by sub-classing GenericType. Alternatively, an object representing a concrete parameterized type can be created using a create(Type) and manually specifying the type() actual (parameterized) type}.

For example:

  GenericType<List<String>> stringListType = new GenericType<List<String>>() {};
 

Or:

  public class MyGenericType extends GenericType<List<String>> { ... }

  ...

  MyGenericType stringListType = new MyGenericType();
 

Note that due to the Java type erasure limitations the parameterized type information must be specified on a subclass, not just during the instance creation. For example, the following case would throw an IllegalArgumentException:

  public class MyGenericType<T> extends GenericType<T> { ... }

  ...

  // The type is only specified on instance, not in a sub-class
  MyGenericType<List<String>> stringListType =
          new MyGenericType<List<String>>();
 

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	GenericType() Constructs a new generic type, deriving the generic type and class from type parameter.

Method Summary

Modifier and Type	Method and Description
T	cast(Object object) Casts the parameter to the type of this generic type.
static <N> GenericType<N>	create(Type genericType) Constructs a new generic type, using the provided generic type information and deriving the class.
boolean	equals(Object obj)
String	getTypeName()
int	hashCode()
boolean	isClass() Whether this generic type represents a simple class with no generic information.
Class<?>	rawType() Returns the object representing the class or interface that declared the type represented by this generic type instance.
Type	type() The type represented by this generic type instance.

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericType

protected GenericType()
               throws IllegalArgumentException

Constructs a new generic type, deriving the generic type and class from type parameter. Note that this constructor is protected, users should create a (usually anonymous) subclass as shown above.

Throws:

IllegalArgumentException - in case the generic type parameter value is not provided by any of the subclasses.

Method Detail

create

public static <N> GenericType<N> create(Type genericType)
                                 throws IllegalArgumentException

Constructs a new generic type, using the provided generic type information and deriving the class.

Type Parameters:

N - generic type of the returned GenericType

Parameters:

genericType - the generic type

Returns:

new type wrapping the provided type

Throws:

IllegalArgumentException - if genericType is null or not an instance of Class or ParameterizedType whose raw type is an instance of Class.

type

public Type type()

The type represented by this generic type instance.

For new GenericType<List<String>>(){}, this would return a ParameterizedType for java.util.List<java.lang.String>.

Returns:

the actual type represented by this generic type instance.

rawType

public Class<?> rawType()

Returns the object representing the class or interface that declared the type represented by this generic type instance.

For new GenericType<List<String>>(){}, this would return an interface java.util.List.

Returns:

the class or interface that declared the type represented by this generic type instance.

isClass

public boolean isClass()

Whether this generic type represents a simple class with no generic information.

Returns:

true if this is a class, false if this is a generic type (e.g. returns true for List, false for List<String>

cast

public T cast(Object object)
       throws ClassCastException

Casts the parameter to the type of this generic type. This is a utility method to use in stream processing etc.

Parameters:

object - instance to cast

Returns:

typed instance

Throws:

ClassCastException - in case the object is not of the expected type

getTypeName

public String getTypeName()

Specified by:

getTypeName in interface Type

hashCode

public int hashCode()

Overrides:

hashCode in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object