0d9ba81c06
Motivation: Attribute.getAndRemove() will return the value but also remove the AttributeKey itself from the AttributeMap. This may not what you want as you may want to keep an instance of it and just set it later again. Document the contract so the user know what to expect. Modifications: - Make it clear when to use AttributeKey.getAndRemove() / AttributeKey.remove() and when AttributeKey.getAndSet(null) / AttributeKey.set(null). Result: Less suprising behaviour.
74 lines
2.4 KiB
Java
74 lines
2.4 KiB
Java
/*
|
|
* Copyright 2012 The Netty Project
|
|
*
|
|
* The Netty Project licenses this file to you 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.netty.util;
|
|
|
|
/**
|
|
* An attribute which allows to store a value reference. It may be updated atomically and so is thread-safe.
|
|
*
|
|
* @param <T> the type of the value it holds.
|
|
*/
|
|
public interface Attribute<T> {
|
|
|
|
/**
|
|
* Returns the key of this attribute.
|
|
*/
|
|
AttributeKey<T> key();
|
|
|
|
/**
|
|
* Returns the current value, which may be {@code null}
|
|
*/
|
|
T get();
|
|
|
|
/**
|
|
* Sets the value
|
|
*/
|
|
void set(T value);
|
|
|
|
/**
|
|
* Atomically sets to the given value and returns the old value which may be {@code null} if non was set before.
|
|
*/
|
|
T getAndSet(T value);
|
|
|
|
/**
|
|
* Atomically sets to the given value if this {@link Attribute}'s value is {@code null}.
|
|
* If it was not possible to set the value as it contains a value it will just return the current value.
|
|
*/
|
|
T setIfAbsent(T value);
|
|
|
|
/**
|
|
* Removes this attribute from the {@link AttributeMap} and returns the old value. Subsequent {@link #get()}
|
|
* calls will return {@code null}.
|
|
*
|
|
* If you only want to return the old value and clear the {@link Attribute} while still keep it in
|
|
* {@link AttributeMap} use {@link #getAndSet(Object)} with a value of {@code null}.
|
|
*/
|
|
T getAndRemove();
|
|
|
|
/**
|
|
* Atomically sets the value to the given updated value if the current value == the expected value.
|
|
* If it the set was successful it returns {@code true} otherwise {@code false}.
|
|
*/
|
|
boolean compareAndSet(T oldValue, T newValue);
|
|
|
|
/**
|
|
* Removes this attribute from the {@link AttributeMap}. Subsequent {@link #get()} calls will return @{code null}.
|
|
*
|
|
* If you only want to remove the value and clear the {@link Attribute} while still keep it in
|
|
* {@link AttributeMap} use {@link #set(Object)} with a value of {@code null}.
|
|
*/
|
|
void remove();
|
|
}
|