/*******************************************************************************
* Copyright (c) 2010-present Sonatype, Inc.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Stuart McCulloch (Sonatype, Inc.) - initial API and implementation
*******************************************************************************/
package org.eclipse.sisu.inject;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import javax.inject.Qualifier;
import com.google.inject.ImplementedBy;
import com.google.inject.Key;
import com.google.inject.ProvidedBy;
import com.google.inject.TypeLiteral;
/**
* Utility methods for dealing with generic type arguments.
*/
public final class TypeArguments
{
// ----------------------------------------------------------------------
// Constants
// ----------------------------------------------------------------------
private static final TypeLiteral<Object> OBJECT_TYPE_LITERAL = TypeLiteral.get( Object.class );
private static final TypeLiteral<?>[] NO_TYPE_LITERALS = {};
// ----------------------------------------------------------------------
// Constructors
// ----------------------------------------------------------------------
private TypeArguments()
{
// static utility class, not allowed to create instances
}
// ----------------------------------------------------------------------
// Utility methods
// ----------------------------------------------------------------------
/**
* Get all type arguments from a generic type, for example {@code [Foo,Bar]} from {@code Map<Foo,Bar>}.
*
* @param typeLiteral The generic type
* @return Array of type arguments
*/
public static TypeLiteral<?>[] get( final TypeLiteral<?> typeLiteral )
{
final Type type = typeLiteral.getType();
if ( type instanceof ParameterizedType )
{
final Type[] argumentTypes = ( (ParameterizedType) type ).getActualTypeArguments();
final TypeLiteral<?>[] argumentLiterals = new TypeLiteral[argumentTypes.length];
for ( int i = 0; i < argumentTypes.length; i++ )
{
argumentLiterals[i] = expand( argumentTypes[i] );
}
return argumentLiterals;
}
if ( type instanceof GenericArrayType )
{
return new TypeLiteral[] { expand( ( (GenericArrayType) type ).getGenericComponentType() ) };
}
return NO_TYPE_LITERALS;
}
/**
* Get an indexed type argument from a generic type, for example {@code Bar} from {@code Map<Foo,Bar>}.
*
* @param typeLiteral The generic type
* @param index The argument index
* @return Indexed type argument; {@code TypeLiteral<Object>} if the given type is a raw class
*/
public static TypeLiteral<?> get( final TypeLiteral<?> typeLiteral, final int index )
{
final Type type = typeLiteral.getType();
if ( type instanceof ParameterizedType )
{
return expand( ( (ParameterizedType) type ).getActualTypeArguments()[index] );
}
if ( type instanceof GenericArrayType )
{
if ( 0 == index )
{
return expand( ( (GenericArrayType) type ).getGenericComponentType() );
}
throw new ArrayIndexOutOfBoundsException( index );
}
return OBJECT_TYPE_LITERAL;
}
/**
* Determines if the sub-type can be converted to the generic super-type via an identity or widening conversion.
*
* @param superLiteral The generic super-type
* @param subLiteral The generic sub-type
* @return {@code true} if the sub-type can be converted to the generic super-type; otherwise {@code false}
* @see Class#isAssignableFrom(Class)
*/
public static boolean isAssignableFrom( final TypeLiteral<?> superLiteral, final TypeLiteral<?> subLiteral )
{
final Class<?> superClazz = superLiteral.getRawType();
if ( !superClazz.isAssignableFrom( subLiteral.getRawType() ) )
{
return false;
}
final Type superType = superLiteral.getType();
if ( superClazz == superType )
{
return true;
}
if ( superType instanceof ParameterizedType )
{
final Type resolvedType = subLiteral.getSupertype( superClazz ).getType();
if ( resolvedType instanceof ParameterizedType )
{
final Type[] superArgs = ( (ParameterizedType) superType ).getActualTypeArguments();
final Type[] subArgs = ( (ParameterizedType) resolvedType ).getActualTypeArguments();
return isAssignableFrom( superArgs, subArgs );
}
}
else if ( superType instanceof GenericArrayType )
{
final Type resolvedType = subLiteral.getSupertype( superClazz ).getType();
if ( resolvedType instanceof GenericArrayType )
{
final Type superComponent = ( (GenericArrayType) superType ).getGenericComponentType();
final Type subComponent = ( (GenericArrayType) resolvedType ).getGenericComponentType();
return isAssignableFrom( new Type[] { superComponent }, new Type[] { subComponent } );
}
}
return false;
}
/**
* Determines if the given generic type represents a concrete type.
*
* @param literal The generic type
* @return {@code true} if the generic type is concrete; otherwise {@code false}
*/
public static boolean isConcrete( final TypeLiteral<?> literal )
{
return isConcrete( literal.getRawType() );
}
/**
* Determines if the given raw type represents a concrete type.
*
* @param clazz The raw type
* @return {@code true} if the raw type is concrete; otherwise {@code false}
*/
public static boolean isConcrete( final Class<?> clazz )
{
return !clazz.isInterface() && !Modifier.isAbstract( clazz.getModifiers() );
}
/**
* Determines if the given generic type represents an implicit binding.
*
* @param literal The generic type
* @return {@code true} if the generic type is implicit; otherwise {@code false}
*/
public static boolean isImplicit( final TypeLiteral<?> literal )
{
return isImplicit( literal.getRawType() );
}
/**
* Determines if the given raw type represents an implicit binding.
*
* @param clazz The raw type
* @return {@code true} if the raw type is implicit; otherwise {@code false}
*/
public static boolean isImplicit( final Class<?> clazz )
{
return isConcrete( clazz ) || clazz.isAnnotationPresent( ImplementedBy.class )
|| clazz.isAnnotationPresent( ProvidedBy.class );
}
/**
* Creates a special binding key for the given implicit type.
*
* @param clazz The implicit type
* @return Implicit binding key
*/
public static <T> Key<T> implicitKey( final Class<T> clazz )
{
return Key.get( clazz, Implicit.class );
}
// ----------------------------------------------------------------------
// Implementation types
// ----------------------------------------------------------------------
/**
* {@link Qualifier} of bindings that should be treated as implicit.
*/
@Qualifier
@Retention( RetentionPolicy.RUNTIME )
private static @interface Implicit
{
}
// ----------------------------------------------------------------------
// Implementation methods
// ----------------------------------------------------------------------
/**
* Expands wild-card types where possible, for example {@code Bar} from {@code ? extends Bar}.
*
* @param type The generic type
* @return Widened type that is still assignment-compatible with the original.
*/
private static TypeLiteral<?> expand( final Type type )
{
if ( type instanceof WildcardType )
{
return TypeLiteral.get( ( (WildcardType) type ).getUpperBounds()[0] );
}
if ( type instanceof TypeVariable<?> )
{
return TypeLiteral.get( ( (TypeVariable<?>) type ).getBounds()[0] );
}
return TypeLiteral.get( type );
}
/**
* Determines whether the resolved sub-type arguments can be assigned to their generic super-type arguments.
*
* @param superArgs The generic super-arguments
* @param subArgs The resolved sub-arguments
* @return {@code true} if all the super-arguments have assignable resolved arguments; otherwise {@code false}
*/
private static boolean isAssignableFrom( final Type[] superArgs, final Type[] subArgs )
{
for ( int i = 0, len = Math.min( superArgs.length, subArgs.length ); i < len; i++ )
{
final Type superType = superArgs[i];
final Type subType = subArgs[i];
/*
* Implementations could have unbound type variables, such as ArrayList<T>. We want to support injecting
* MyList<T extends Number> into List<Double> which is why we reverse the following expanded arguments:
*/
if ( subType instanceof TypeVariable<?> && isAssignableFrom( expand( subType ), expand( superType ) ) )
{
continue;
}
/*
* Interfaces can have wild-card types, such as List<? extends Number>. Note: we only check the initial
* upper-bound of the super-type against the resolved type (trading absolute accuracy for performance).
*/
if ( superType instanceof WildcardType || superType instanceof TypeVariable<?> )
{
if ( !isAssignableFrom( expand( superType ), expand( subType ) ) )
{
return false;
}
}
/*
* Non-wild-card arguments must be tested with equals: List<Number> is not assignable from List<Float>.
*/
else if ( !superType.equals( subType ) )
{
return false;
}
}
return true;
}
}