/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.undertow.util;
/**
* @author Stuart Douglas
*/
/**
* An immutable, type-safe object attachment key. Such a key has no value outside of its object identity.
*
* @param <T> the attachment type
*/
public abstract class
AttachmentKey<T> {
AttachmentKey() {
}
/**
* Cast the value to the type of this attachment key.
*
* @param value the value
* @return the cast value
*/
public abstract T
cast(
Object value);
/**
* Construct a new simple attachment key.
*
* @param valueClass the value class
* @param <T> the attachment type
* @return the new instance
*/
public static <T>
AttachmentKey<T>
create(final
Class<? super T>
valueClass) {
return new
SimpleAttachmentKey(
valueClass);
}
/**
* Construct a new list attachment key.
*
* @param valueClass the list value class
* @param <T> the list value type
* @return the new instance
*/
@
SuppressWarnings("unchecked")
public static <T>
AttachmentKey<
AttachmentList<T>>
createList(final
Class<? super T>
valueClass) {
return new
ListAttachmentKey(
valueClass);
}
}
class
ListAttachmentKey<T> extends
AttachmentKey<
AttachmentList<T>> {
private final
Class<T>
valueClass;
ListAttachmentKey(final
Class<T>
valueClass) {
this.
valueClass =
valueClass;
}
@
SuppressWarnings({"unchecked"})
public
AttachmentList<T>
cast(final
Object value) {
if (
value == null) {
return null;
}
AttachmentList<?>
list = (
AttachmentList<?>)
value;
final
Class<?>
listValueClass =
list.
getValueClass();
if (
listValueClass !=
valueClass) {
throw new
ClassCastException();
}
return (
AttachmentList<T>)
list;
}
Class<T>
getValueClass() {
return
valueClass;
}
}