Created
May 16, 2022 08:34
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Reflection based record wither prototype
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interface Wither<T extends Record> { | |
default <V> T with( SerializableSupplier<V> accessor, V newValue ) { | |
try { | |
var providedAccessor = accessor.method( ); | |
var components = R.class.getRecordComponents( ); | |
var accessors = Arrays.stream( components ) | |
.map( RecordComponent::getAccessor ) | |
.toArray( ); | |
Object[ ] arguments = new Object[ components.length ]; | |
for( int i = 0; i < accessors.length; i++ ) { | |
if( accessors[ i ].equals( providedAccessor ) ) { | |
arguments[ i ] = newValue; | |
} else { | |
arguments[ i ] = components[ i ].getAccessor( ).invoke( this ); | |
} | |
} | |
var ctor = R.class.getDeclaredConstructors( )[ 0 ]; | |
return ( T ) ctor.newInstance( arguments ); | |
} catch( IllegalAccessException | InvocationTargetException | InstantiationException e ) { | |
throw new RuntimeException( e ); | |
} | |
} | |
} | |
interface SerializableSupplier<T> extends Supplier<T>, Serializable, MethodReferenceReflection { | |
} | |
interface MethodReferenceReflection { | |
default SerializedLambda serialized( ) { | |
try { | |
Method replaceMethod = getClass( ).getDeclaredMethod( "writeReplace" ); | |
replaceMethod.setAccessible( true ); | |
return ( SerializedLambda ) replaceMethod.invoke( this ); | |
} catch( Exception e ) { | |
throw new RuntimeException( e ); | |
} | |
} | |
default Class<?> getContainingClass( ) { | |
try { | |
String className = serialized( ).getImplClass( ).replaceAll( "/", "." ); | |
return Class.forName( className ); | |
} catch( Exception e ) { | |
throw new RuntimeException( e ); | |
} | |
} | |
default Method method( ) { | |
SerializedLambda lambda = serialized( ); | |
Class<?> containingClass = getContainingClass( ); | |
return Arrays.stream( containingClass.getDeclaredMethods( ) ) | |
.filter( method -> Objects.equals( method.getName( ), lambda.getImplMethodName( ) ) ) | |
.findFirst( ) | |
.orElseThrow( UnableToGuessMethodException::new ); | |
} | |
class UnableToGuessMethodException extends RuntimeException { | |
} | |
} |
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