io.undertow.util.AttachmentKey Maven / Gradle / Ivy
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* 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 the attachment type
*/
public abstract class AttachmentKey {
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 the attachment type
* @return the new instance
*/
public static AttachmentKey create(final Class valueClass) {
return new SimpleAttachmentKey(valueClass);
}
/**
* Construct a new list attachment key.
*
* @param valueClass the list value class
* @param the list value type
* @return the new instance
*/
@SuppressWarnings("unchecked")
public static AttachmentKey> createList(final Class valueClass) {
return new ListAttachmentKey(valueClass);
}
}
class ListAttachmentKey extends AttachmentKey> {
private final Class valueClass;
ListAttachmentKey(final Class valueClass) {
this.valueClass = valueClass;
}
@SuppressWarnings({"unchecked"})
public AttachmentList 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) list;
}
Class getValueClass() {
return valueClass;
}
}