Java TypeVariable類代碼示例

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
private static ResolvableType resolveVariable(TypeVariable<?> typeVariable, ResolvableType contextType) {
    ResolvableType resolvedType;
    if (contextType.hasGenerics()) {
        resolvedType = ResolvableType.forType(typeVariable, contextType);
        if (resolvedType.resolve() != null) {
            return resolvedType;
        }
    }

    ResolvableType superType = contextType.getSuperType();
    if (superType != ResolvableType.NONE) {
        resolvedType = resolveVariable(typeVariable, superType);
        if (resolvedType.resolve() != null) {
            return resolvedType;
        }
    }
    for (ResolvableType ifc : contextType.getInterfaces()) {
        resolvedType = resolveVariable(typeVariable, ifc);
        if (resolvedType.resolve() != null) {
            return resolvedType;
        }
    }
    return ResolvableType.NONE;
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
@Override
public String toString() {
	StringBuilder sb = new StringBuilder();
	Class<?> rawType = getRawType();
	if (!rawType.isArray()) {
		sb.append(rawType.getName());
	} else {
		sb.append(rawType.getComponentType().getName());
	}
	TypeVariable<? extends Class<?>>[] typeParameters = rawType.getTypeParameters();
	if (typeParameters.length > 0) {
		sb.append("<");
		for (int i = 0; i < typeParameters.length; i++) {
			if (i > 0) {
				sb.append(", ");
			}
			String s = this.getParam(i).toParamString();
			sb.append(s);
		}
		sb.append(">");
	}
	if (rawType.isArray()) {
		sb.append("[]");
	}
	return sb.toString();
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
public static Class<?> getClass(Type type){
    if(type.getClass() == Class.class){
        return (Class<?>) type;
    }

    if(type instanceof ParameterizedType){
        return getClass(((ParameterizedType) type).getRawType());
    }

    if(type instanceof TypeVariable){
        Type boundType = ((TypeVariable<?>) type).getBounds()[0];
        return (Class<?>) boundType;
    }

    if(type instanceof WildcardType){
        Type[] upperBounds = ((WildcardType) type).getUpperBounds();
        if (upperBounds.length == 1) {
            return getClass(upperBounds[0]);
        }
    }

    return Object.class;
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
protected static Class getTypeClass(final Type type, final Map<TypeVariable<?>, Type> typeArgs) {
    Type rawType = type;
    if (type instanceof ParameterizedType) {
        rawType = ((ParameterizedType) type).getRawType();
    }

    if (rawType instanceof Class) {
        return (Class) rawType;
    }


    if (rawType instanceof TypeVariable) {
        final Type t = typeArgs.get(rawType);
        if (null != t) {
            return getTypeClass(t, typeArgs);
        }
    }
    // cannot resolve - default to UnknownGenericType;
    return UnknownGenericType.class;
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
private static void checkOneParameterType(ParameterizedType toCheck, Class<?> rawType,
    Class<?>... bounds) {
  System.out.println(((Class<?>) toCheck.getRawType()).getName()
      .equals(rawType.getName()));
  Type[] parameters = toCheck.getActualTypeArguments();
  System.out.println(parameters.length);
  TypeVariable<?> parameter = (TypeVariable<?>) parameters[0];
  System.out.println(parameter.getName());
  Type[] actualBounds = parameter.getBounds();
  for (int i = 0; i < bounds.length; i++) {
    System.out.println(((Class<?>) actualBounds[i]).getName().equals(bounds[i].getName()));
  }
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
/**
 * Constructs a new type literal. Derives represented class from type
 * parameter.
 * 
 * <p>
 * Clients create an empty anonymous subclass. Doing so embeds the type
 * parameter in the anonymous class's type hierarchy so we can reconstitute
 * it at runtime despite erasure.
 */
public TypeLiteral() {
	ParameterizedType genClass = (ParameterizedType) getClass().getGenericSuperclass();
	Type[] types = genClass.getActualTypeArguments();
	if (types == null || types.length == 0) {
		throw new RuntimeException("TypeLiteral<T> must have a specfied type <T>");
	}
	this.type = types[0];
	if (this.type instanceof GenericArrayType)
		throw new RuntimeException("TypeLiteral does not support GenericArrayTypes, use Injector.get(ComponentType[].class)");
	if (this.type instanceof TypeVariable)
		throw new RuntimeException("TypeLiteral does not support TypeVariables");
	
	if (type instanceof Class) {
		this.rawType = (Class<T>) this.type;
	} else if (type instanceof ParameterizedType) {
		this.rawType =  (Class<T>) ((ParameterizedType) type).getRawType();
	} else {
		this.rawType = Object.class;
	}
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
public static Class getGenericClass(ParameterizedType parameterizedType, int i) {
    Object genericClass = parameterizedType.getActualTypeArguments()[i];
    if (genericClass instanceof ParameterizedType) { // 處理多級泛型
        return (Class) ((ParameterizedType) genericClass).getRawType();
    } else if (genericClass instanceof GenericArrayType) { // 處理數組泛型
        return (Class) ((GenericArrayType) genericClass).getGenericComponentType();
    } else if (genericClass instanceof TypeVariable) { // 處理泛型擦拭對象
        return (Class) getClass(((TypeVariable) genericClass).getBounds()[0], 0);
    } else {
        return (Class) genericClass;
    }
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
public void testNewTypeVariable() throws Exception {
  TypeVariable<?> noBoundJvmType =
      WithTypeVariable.getTypeVariable("withoutBound");
  TypeVariable<?> objectBoundJvmType =
      WithTypeVariable.getTypeVariable("withObjectBound");
  TypeVariable<?> upperBoundJvmType =
      WithTypeVariable.getTypeVariable("withUpperBound");
  TypeVariable<?> noBound = withBounds(noBoundJvmType);
  TypeVariable<?> objectBound = withBounds(objectBoundJvmType, Object.class);
  TypeVariable<?> upperBound = withBounds(
      upperBoundJvmType, Number.class, CharSequence.class);

  assertEqualTypeVariable(noBoundJvmType, noBound);
  assertEqualTypeVariable(noBoundJvmType,
      withBounds(noBoundJvmType, Object.class));
  assertEqualTypeVariable(objectBoundJvmType, objectBound);
  assertEqualTypeVariable(upperBoundJvmType, upperBound);

  new TypeVariableEqualsTester()
      .addEqualityGroup(noBoundJvmType, noBound)
      .addEqualityGroup(objectBoundJvmType, objectBound)
      .addEqualityGroup(upperBoundJvmType, upperBound)
      .testEquals();
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
static boolean hasUnresolvableType(Type type) {
    if (type instanceof Class<?>) {
        return false;
    }
    if (type instanceof ParameterizedType) {
        ParameterizedType parameterizedType = (ParameterizedType) type;
        for (Type typeArgument : parameterizedType.getActualTypeArguments()) {
            if (hasUnresolvableType(typeArgument)) {
                return true;
            }
        }
        return false;
    }
    if (type instanceof GenericArrayType) {
        return hasUnresolvableType(((GenericArrayType) type).getGenericComponentType());
    }
    if (type instanceof TypeVariable) {
        return true;
    }
    if (type instanceof WildcardType) {
        return true;
    }
    String className = type == null ? "null" : type.getClass().getName();
    throw new IllegalArgumentException("Expected a Class, ParameterizedType, or "
            + "GenericArrayType, but <" + type + "> is of type " + className);
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
public static Type getInheritGenericType(Class<?> clazz, TypeVariable<?> tv) {
    Type type = null;
    GenericDeclaration gd = tv.getGenericDeclaration();
    do {
        type = clazz.getGenericSuperclass();
        if (type == null) {
            return null;
        }
        if (type instanceof ParameterizedType) {
            ParameterizedType ptype = (ParameterizedType) type;
            if (ptype.getRawType() == gd) {
                TypeVariable<?>[] tvs = gd.getTypeParameters();
                Type[] types = ptype.getActualTypeArguments();
                for (int i = 0; i < tvs.length; i++) {
                    if (tvs[i] == tv) return types[i];
                }
                return null;
            }
        }
        clazz = TypeUtils.getClass(type);
    } while (type != null);
    return null;
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
/**
 * Resolves all type variables in {@code type} and all downstream types and returns a
 * corresponding type with type variables resolved.
 */
public Type resolveType(Type type) {
  checkNotNull(type);
  if (type instanceof TypeVariable) {
    return typeTable.resolve((TypeVariable<?>) type);
  } else if (type instanceof ParameterizedType) {
    return resolveParameterizedType((ParameterizedType) type);
  } else if (type instanceof GenericArrayType) {
    return resolveGenericArrayType((GenericArrayType) type);
  } else if (type instanceof WildcardType) {
    return resolveWildcardType((WildcardType) type);
  } else {
    // if Class<?>, no resolution needed, we are done.
    return type;
  }
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
private WildcardCapturer forTypeVariable(final TypeVariable<?> typeParam) {
  return new WildcardCapturer(id) {
    @Override TypeVariable<?> captureAsTypeVariable(Type[] upperBounds) {
      Set<Type> combined = new LinkedHashSet<>(asList(upperBounds));
      // Since this is an artifically generated type variable, we don't bother checking
      // subtyping between declared type bound and actual type bound. So it's possible that we
      // may generate something like <capture#1-of ? extends Foo&SubFoo>.
      // Checking subtype between declared and actual type bounds
      // adds recursive isSubtypeOf() call and feels complicated.
      // There is no contract one way or another as long as isSubtypeOf() works as expected.
      combined.addAll(asList(typeParam.getBounds()));
      if (combined.size() > 1) { // Object is implicit and only useful if it's the only bound.
        combined.remove(Object.class);
      }
      return super.captureAsTypeVariable(combined.toArray(new Type[0]));
    }
  };
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
private static Signature createSignature(final Object input, final Type type, final Map<TypeVariable<?>, Type> typeArgs, final boolean isInput) {
    final Class clazz = getTypeClass(type, typeArgs);

    if (Tuple.class.isAssignableFrom(clazz)) {
        final TypeVariable[] tupleTypes = getTypeClass(type, typeArgs).getTypeParameters();
        final Map<TypeVariable<?>, Type> classTypeArgs = TypeUtils.getTypeArguments(type, clazz);
        Collection<? extends Type> types = TypeUtils.getTypeArguments(type, clazz).values();
        Class[] classes = new Class[types.size()];
        int i = 0;
        for (final TypeVariable tupleType : tupleTypes) {
            classes[i++] = getTypeClass(classTypeArgs.get(tupleType), typeArgs);
        }

        return new TupleSignature(input, clazz, classes, isInput);
    }

    return new SingletonSignature(input, clazz, isInput);
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
private static Type substituteTypeVariables(Map<String, Type> lookup, Type type) {
    if (type instanceof TypeVariable) {
        return translateTypeVariable(lookup, (TypeVariable) type);
    }
    if (type instanceof ParameterizedType) {
        ParameterizedType pType = (ParameterizedType) type;
        Type[] args = pType.getActualTypeArguments();
        for (int i = 0; i < args.length; i++) {
            args[i] = substituteTypeVariables(lookup, args[i]);
        }
        return new ParameterizedTypeImpl(args, pType.getOwnerType(), pType.getRawType());
    }
    if (type instanceof GenericArrayType) {
        GenericArrayType gaType = (GenericArrayType) type;
        return new GenericArrayTypeImpl(substituteTypeVariables(lookup, gaType.getGenericComponentType()));
    }
    return type;
}
 

import java.lang.reflect.TypeVariable; //導入依賴的package包/類
/**
 * Returns the generic superclass of this type or {@code null} if the type represents
 * {@link Object} or an interface. This method is similar but different from
 * {@link Class#getGenericSuperclass}. For example, {@code new TypeToken<StringArrayList>()
 * {}.getGenericSuperclass()} will return {@code new TypeToken<ArrayList<String>>() {}}; while
 * {@code StringArrayList.class.getGenericSuperclass()} will return {@code ArrayList<E>}, where
 * {@code E} is the type variable declared by class {@code ArrayList}.
 *
 * <p>If this type is a type variable or wildcard, its first upper bound is examined and returned
 * if the bound is a class or extends from a class. This means that the returned type could be a
 * type variable too.
 */
@Nullable
final TypeToken<? super T> getGenericSuperclass() {
  if (runtimeType instanceof TypeVariable) {
    // First bound is always the super class, if one exists.
    return boundAsSuperclass(((TypeVariable<?>) runtimeType).getBounds()[0]);
  }
  if (runtimeType instanceof WildcardType) {
    // wildcard has one and only one upper bound.
    return boundAsSuperclass(((WildcardType) runtimeType).getUpperBounds()[0]);
  }
  Type superclass = getRawType().getGenericSuperclass();
  if (superclass == null) {
    return null;
  }
  @SuppressWarnings("unchecked") // super class of T
  TypeToken<? super T> superToken = (TypeToken<? super T>) resolveSupertype(superclass);
  return superToken;
}