io.undertow.util.Attachable 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;
import java.util.List;
/**
* A thing which can have named attachments.
*
* @author David M. Lloyd
*/
public interface Attachable {
/**
* Get an attachment value. If no attachment exists for this key, {@code null} is returned.
*
* @param key the attachment key
* @param the value type
* @return the value, or {@code null} if there is none
*/
T getAttachment(AttachmentKey key);
/**
* Gets a list attachment value. If not attachment exists for this key an empty list is returned
*
* @param the value type
* @param key the attachment key
* @return the value, or an empty list if there is none
*/
List getAttachmentList(AttachmentKey> key);
/**
* Set an attachment value. If an attachment for this key was already set, return the original value. If the value being set
* is {@code null}, the attachment key is removed.
*
* @param key the attachment key
* @param value the new value
* @param the value type
* @return the old value, or {@code null} if there was none
*/
T putAttachment(AttachmentKey key, T value);
/**
* Remove an attachment, returning its previous value.
*
* @param key the attachment key
* @param the value type
* @return the old value, or {@code null} if there was none
*/
T removeAttachment(AttachmentKey key);
/**
* Add a value to a list-typed attachment key. If the key is not mapped, add such a mapping.
*
* @param key the attachment key
* @param value the value to add
* @param the list value type
*/
void addToAttachmentList(AttachmentKey> key, T value);
}