org.apache.qpid.proton.engine.ExtendableAccessor Maven / Gradle / Ivy
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF 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 org.apache.qpid.proton.engine;
/**
* A typesafe convenience class for associating additional data with {@link Extendable} classes.
*
* An instance of ExtendableAccessor uses itself as the key in the {@link Extendable#attachments()}
* so it's best instantiated as a static final member.
*
* class Foo extends BaseHandler {
* private static ExtendableAccessor<Link, Bar> LINK_BAR = new ExtendableAccessor<>(Bar.class);
* void onLinkRemoteOpen(Event e) {
* Bar bar = LINK_BAR.get(e.getLink());
* if (bar == null) {
* bar = new Bar();
* LINK_BAR.set(e.getLink(), bar);
* }
* }
* }
*
*
* @param An {@link Extendable} type where the data is to be stored
* @param The type of the data to be stored
*/
public final class ExtendableAccessor {
private final Class klass;
public ExtendableAccessor(Class klass) {
this.klass = klass;
}
public T get(E e) {
return e.attachments().get(this, klass);
}
public void set(E e, T value) {
e.attachments().set(this, klass, value);
}
}