Module dk.cloudcreate.essentials.shared

Package dk.cloudcreate.essentials.shared.types

Class GenericType<T>

java.lang.Object

dk.cloudcreate.essentials.shared.types.GenericType<T>

Type Parameters:

T - the type provided to the GenericType

public abstract class GenericType<T>
extends Object

Using this class makes it possible to capture a generic/parameterized argument type, such as List<Money>, instead of having to rely on the classical .class construct.
When you specify a type reference using .class you loose any Generic/Parameterized information, as you cannot write List<Money>.class, only List.class.

With GenericType you can specify and capture parameterized type information

You can specify a parameterized type using GenericType:

var genericType = new GenericType<List<Money>>(){};

The type/getType() will return List.class
And genericType/getGenericType() will return ParameterizedType, which can be introspected further

You can also supply a non-parameterized type to GenericType:

var genericType = new GenericType<Money>(){};

In which case type/getType() will return Money.class
And genericType/getGenericType() will return Money.class

Field Summary

Fields

Modifier and Type	Field	Description
final Type	genericType
final Class<T>	type

Constructor Summary

Constructors

Constructor	Description
GenericType()

Method Summary

Modifier and Type	Method	Description
Type	getGenericType()
Class<T>	getType()
static Class<?>	resolveGenericTypeForInterface(Class<?> forType, Class<?> withGenericInterface, int typeArgumentIndex)	Resolve a specific parameterized type argument typeArgumentIndex for a given forType which implements a generic/parameterize interface withGenericInterface Example: Given this withGenericInterface:
static Class<?>	resolveGenericTypeOnSuperClass(Class<?> forType, int typeArgumentIndex)	Resolve the concrete parameterized type a given forType has specified with its direct super class. Example: Given super-class: class AggregateRoot<ID, AGGREGATE_TYPE extends AggregateRoot<ID, AGGREGATE_TYPE>> implements Aggregate<ID> And sub/concrete class: class Order extends AggregateRoot<OrderId, Order> Then: GenericType.resolveGenericType(Order.class, 0) will return OrderId.class and GenericType.resolveGenericType(Order.class, 1) will return Order.class

Methods inherited from class java.lang.Object

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

Field Details

type

public final Class<T> type

genericType

public final Type genericType

Constructor Details

GenericType

public GenericType()

Method Details

getType

public Class<T> getType()

getGenericType

public Type getGenericType()

resolveGenericTypeOnSuperClass

public static Class<?> resolveGenericTypeOnSuperClass(Class<?> forType,
 int typeArgumentIndex)

Resolve the concrete parameterized type a given forType has specified with its direct super class.
Example:
Given super-class:
class AggregateRoot<ID, AGGREGATE_TYPE extends AggregateRoot<ID, AGGREGATE_TYPE>> implements Aggregate<ID>

And sub/concrete class:
class Order extends AggregateRoot<OrderId, Order>

Then:
GenericType.resolveGenericType(Order.class, 0) will return OrderId.class

and
GenericType.resolveGenericType(Order.class, 1) will return Order.class

Parameters:

forType - the type that is specifying a parameterized type with its super-class

typeArgumentIndex - the index in the superclasses type parameters (0 based)

Returns:

an optional with the parameterized type or Optional.empty() if the type couldn't resolved

resolveGenericTypeForInterface

public static Class<?> resolveGenericTypeForInterface(Class<?> forType,
 Class<?> withGenericInterface,
 int typeArgumentIndex)

Resolve a specific parameterized type argument typeArgumentIndex for a given forType which implements a generic/parameterize interface withGenericInterface
Example:
Given this withGenericInterface:

 public interface WithState<ID, AGGREGATE_TYPE extends AggregateRoot<ID, AGGREGATE_TYPE>, AGGREGATE_STATE extends AggregateState<ID, AGGREGATE_TYPE>> {
 }
 

and this forType:

 public static class Order extends AggregateRoot<String, Order> implements WithState<String, Order, OrderState> {
 }
 

then calling

 var actualType = GenericType.resolveGenericTypeForInterface(Order.class,
                                                             WithState.class,
                                                             typeArgumentIndex);
 

with these typeArgumentIndex will yield the following results:

typeArgumentIndex	Returned generic type
0	String.class
1	Order.class
2	OrderState.class
3	throws IllegalArgumentException

Parameters:

forType - the type that implement the withGenericInterface

withGenericInterface - the parameterized/generic interface that specifies a parameterized type at index typeArgumentIndex

typeArgumentIndex - the parameterized argument index (0 based)

Returns:

the type

Throws:

IllegalStateException - in case the type doesn't extend the interface, the interface isn't generic

IllegalArgumentException - if the interface doesn't specify a parameterized argument with the specified index