277 lines
8.6 KiB
Java
277 lines
8.6 KiB
Java
// Copyright (C) 2012 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package com.google.gerrit.extensions.registration;
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import com.google.inject.Binder;
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import com.google.inject.Key;
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import com.google.inject.Provider;
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import com.google.inject.Scopes;
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import com.google.inject.TypeLiteral;
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import com.google.inject.binder.LinkedBindingBuilder;
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import com.google.inject.internal.UniqueAnnotations;
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import com.google.inject.name.Named;
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import com.google.inject.util.Providers;
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import com.google.inject.util.Types;
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import java.util.Collection;
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import java.util.Collections;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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import java.util.concurrent.CopyOnWriteArrayList;
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import java.util.concurrent.atomic.AtomicReference;
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/**
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* A set of members that can be modified as plugins reload.
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*
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* <p>DynamicSets are always mapped as singletons in Guice. Sets store Providers internally, and
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* resolve the provider to an instance on demand. This enables registrations to decide between
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* singleton and non-singleton members.
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*/
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public class DynamicSet<T> implements Iterable<T> {
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/**
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* Declare a singleton {@code DynamicSet<T>} with a binder.
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*
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* <p>Sets must be defined in a Guice module before they can be bound:
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*
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* <pre>
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* DynamicSet.setOf(binder(), Interface.class);
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* DynamicSet.bind(binder(), Interface.class).to(Impl.class);
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* </pre>
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*
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* @param binder a new binder created in the module.
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* @param member type of entry in the set.
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*/
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public static <T> void setOf(Binder binder, Class<T> member) {
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binder.disableCircularProxies();
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setOf(binder, TypeLiteral.get(member));
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}
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/**
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* Declare a singleton {@code DynamicSet<T>} with a binder.
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*
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* <p>Sets must be defined in a Guice module before they can be bound:
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*
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* <pre>
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* DynamicSet.setOf(binder(), new TypeLiteral<Thing<Foo>>() {});
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* </pre>
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*
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* @param binder a new binder created in the module.
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* @param member type of entry in the set.
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*/
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public static <T> void setOf(Binder binder, TypeLiteral<T> member) {
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@SuppressWarnings("unchecked")
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Key<DynamicSet<T>> key =
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(Key<DynamicSet<T>>)
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Key.get(Types.newParameterizedType(DynamicSet.class, member.getType()));
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binder.disableCircularProxies();
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binder.bind(key).toProvider(new DynamicSetProvider<>(member)).in(Scopes.SINGLETON);
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}
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/**
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* Bind one implementation into the set using a unique annotation.
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*
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* @param binder a new binder created in the module.
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* @param type type of entries in the set.
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* @return a binder to continue configuring the new set member.
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*/
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public static <T> LinkedBindingBuilder<T> bind(Binder binder, Class<T> type) {
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binder.disableCircularProxies();
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return bind(binder, TypeLiteral.get(type));
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}
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/**
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* Bind one implementation into the set using a unique annotation.
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*
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* @param binder a new binder created in the module.
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* @param type type of entries in the set.
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* @return a binder to continue configuring the new set member.
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*/
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public static <T> LinkedBindingBuilder<T> bind(Binder binder, TypeLiteral<T> type) {
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binder.disableCircularProxies();
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return binder.bind(type).annotatedWith(UniqueAnnotations.create());
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}
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/**
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* Bind a named implementation into the set.
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*
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* @param binder a new binder created in the module.
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* @param type type of entries in the set.
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* @param name {@code @Named} annotation to apply instead of a unique annotation.
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* @return a binder to continue configuring the new set member.
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*/
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public static <T> LinkedBindingBuilder<T> bind(Binder binder, Class<T> type, Named name) {
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binder.disableCircularProxies();
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return bind(binder, TypeLiteral.get(type));
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}
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/**
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* Bind a named implementation into the set.
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*
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* @param binder a new binder created in the module.
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* @param type type of entries in the set.
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* @param name {@code @Named} annotation to apply instead of a unique annotation.
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* @return a binder to continue configuring the new set member.
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*/
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public static <T> LinkedBindingBuilder<T> bind(Binder binder, TypeLiteral<T> type, Named name) {
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binder.disableCircularProxies();
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return binder.bind(type).annotatedWith(name);
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}
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public static <T> DynamicSet<T> emptySet() {
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return new DynamicSet<>(Collections.<AtomicReference<Provider<T>>>emptySet());
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}
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private final CopyOnWriteArrayList<AtomicReference<Provider<T>>> items;
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DynamicSet(Collection<AtomicReference<Provider<T>>> base) {
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items = new CopyOnWriteArrayList<>(base);
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}
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public DynamicSet() {
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this(Collections.<AtomicReference<Provider<T>>>emptySet());
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}
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@Override
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public Iterator<T> iterator() {
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final Iterator<AtomicReference<Provider<T>>> itr = items.iterator();
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return new Iterator<T>() {
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private T next;
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@Override
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public boolean hasNext() {
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while (next == null && itr.hasNext()) {
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Provider<T> p = itr.next().get();
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if (p != null) {
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try {
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next = p.get();
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} catch (RuntimeException e) {
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// TODO Log failed member of DynamicSet.
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}
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}
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}
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return next != null;
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}
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@Override
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public T next() {
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if (hasNext()) {
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T result = next;
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next = null;
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return result;
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}
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throw new NoSuchElementException();
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}
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@Override
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public void remove() {
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throw new UnsupportedOperationException();
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}
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};
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}
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/**
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* Returns {@code true} if this set contains the given item.
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*
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* @param item item to check whether or not it is contained.
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* @return {@code true} if this set contains the given item.
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*/
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public boolean contains(T item) {
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Iterator<T> iterator = iterator();
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while (iterator.hasNext()) {
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T candidate = iterator.next();
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if (candidate == item) {
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return true;
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}
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}
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return false;
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}
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/**
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* Add one new element to the set.
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*
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* @param item the item to add to the collection. Must not be null.
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* @return handle to remove the item at a later point in time.
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*/
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public RegistrationHandle add(T item) {
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return add(Providers.of(item));
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}
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/**
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* Add one new element to the set.
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*
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* @param item the item to add to the collection. Must not be null.
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* @return handle to remove the item at a later point in time.
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*/
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public RegistrationHandle add(Provider<T> item) {
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final AtomicReference<Provider<T>> ref = new AtomicReference<>(item);
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items.add(ref);
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return new RegistrationHandle() {
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@Override
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public void remove() {
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if (ref.compareAndSet(item, null)) {
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items.remove(ref);
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}
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}
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};
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}
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/**
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* Add one new element that may be hot-replaceable in the future.
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*
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* @param key unique description from the item's Guice binding. This can be later obtained from
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* the registration handle to facilitate matching with the new equivalent instance during a
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* hot reload.
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* @param item the item to add to the collection right now. Must not be null.
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* @return a handle that can remove this item later, or hot-swap the item without it ever leaving
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* the collection.
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*/
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public ReloadableRegistrationHandle<T> add(Key<T> key, Provider<T> item) {
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AtomicReference<Provider<T>> ref = new AtomicReference<>(item);
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items.add(ref);
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return new ReloadableHandle(ref, key, item);
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}
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private class ReloadableHandle implements ReloadableRegistrationHandle<T> {
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private final AtomicReference<Provider<T>> ref;
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private final Key<T> key;
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private final Provider<T> item;
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ReloadableHandle(AtomicReference<Provider<T>> ref, Key<T> key, Provider<T> item) {
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this.ref = ref;
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this.key = key;
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this.item = item;
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}
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@Override
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public void remove() {
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if (ref.compareAndSet(item, null)) {
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items.remove(ref);
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}
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}
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@Override
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public Key<T> getKey() {
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return key;
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}
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@Override
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public ReloadableHandle replace(Key<T> newKey, Provider<T> newItem) {
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if (ref.compareAndSet(item, newItem)) {
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return new ReloadableHandle(ref, newKey, newItem);
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}
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return null;
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}
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}
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}
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