com.google.gerrit.extensions.registration.DynamicSet Maven / Gradle / Ivy
// Copyright (C) 2012 The Android Open Source Project
//
// 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 com.google.gerrit.extensions.registration;
import com.google.inject.Binder;
import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.Scopes;
import com.google.inject.TypeLiteral;
import com.google.inject.binder.LinkedBindingBuilder;
import com.google.inject.internal.UniqueAnnotations;
import com.google.inject.name.Named;
import com.google.inject.util.Providers;
import com.google.inject.util.Types;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicReference;
/**
* A set of members that can be modified as plugins reload.
*
* DynamicSets are always mapped as singletons in Guice. Sets store Providers internally, and
* resolve the provider to an instance on demand. This enables registrations to decide between
* singleton and non-singleton members.
*/
public class DynamicSet implements Iterable {
/**
* Declare a singleton {@code DynamicSet} with a binder.
*
* Sets must be defined in a Guice module before they can be bound:
*
*
* DynamicSet.setOf(binder(), Interface.class);
* DynamicSet.bind(binder(), Interface.class).to(Impl.class);
*
*
* @param binder a new binder created in the module.
* @param member type of entry in the set.
*/
public static void setOf(Binder binder, Class member) {
binder.disableCircularProxies();
setOf(binder, TypeLiteral.get(member));
}
/**
* Declare a singleton {@code DynamicSet} with a binder.
*
* Sets must be defined in a Guice module before they can be bound:
*
*
* DynamicSet.setOf(binder(), new TypeLiteral<Thing<Foo>>() {});
*
*
* @param binder a new binder created in the module.
* @param member type of entry in the set.
*/
public static void setOf(Binder binder, TypeLiteral member) {
@SuppressWarnings("unchecked")
Key> key =
(Key>)
Key.get(Types.newParameterizedType(DynamicSet.class, member.getType()));
binder.disableCircularProxies();
binder.bind(key).toProvider(new DynamicSetProvider<>(member)).in(Scopes.SINGLETON);
}
/**
* Bind one implementation into the set using a unique annotation.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @return a binder to continue configuring the new set member.
*/
public static LinkedBindingBuilder bind(Binder binder, Class type) {
binder.disableCircularProxies();
return bind(binder, TypeLiteral.get(type));
}
/**
* Bind one implementation into the set using a unique annotation.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @return a binder to continue configuring the new set member.
*/
public static LinkedBindingBuilder bind(Binder binder, TypeLiteral type) {
binder.disableCircularProxies();
return binder.bind(type).annotatedWith(UniqueAnnotations.create());
}
/**
* Bind a named implementation into the set.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @param name {@code @Named} annotation to apply instead of a unique annotation.
* @return a binder to continue configuring the new set member.
*/
public static LinkedBindingBuilder bind(Binder binder, Class type, Named name) {
binder.disableCircularProxies();
return bind(binder, TypeLiteral.get(type));
}
/**
* Bind a named implementation into the set.
*
* @param binder a new binder created in the module.
* @param type type of entries in the set.
* @param name {@code @Named} annotation to apply instead of a unique annotation.
* @return a binder to continue configuring the new set member.
*/
public static LinkedBindingBuilder bind(Binder binder, TypeLiteral type, Named name) {
binder.disableCircularProxies();
return binder.bind(type).annotatedWith(name);
}
public static DynamicSet emptySet() {
return new DynamicSet<>(Collections.>>emptySet());
}
private final CopyOnWriteArrayList>> items;
DynamicSet(Collection>> base) {
items = new CopyOnWriteArrayList<>(base);
}
public DynamicSet() {
this(Collections.>>emptySet());
}
@Override
public Iterator iterator() {
final Iterator>> itr = items.iterator();
return new Iterator() {
private T next;
@Override
public boolean hasNext() {
while (next == null && itr.hasNext()) {
Provider p = itr.next().get();
if (p != null) {
try {
next = p.get();
} catch (RuntimeException e) {
// TODO Log failed member of DynamicSet.
}
}
}
return next != null;
}
@Override
public T next() {
if (hasNext()) {
T result = next;
next = null;
return result;
}
throw new NoSuchElementException();
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
/**
* Returns {@code true} if this set contains the given item.
*
* @param item item to check whether or not it is contained.
* @return {@code true} if this set contains the given item.
*/
public boolean contains(final T item) {
Iterator iterator = iterator();
while (iterator.hasNext()) {
T candidate = iterator.next();
if (candidate == item) {
return true;
}
}
return false;
}
/**
* Add one new element to the set.
*
* @param item the item to add to the collection. Must not be null.
* @return handle to remove the item at a later point in time.
*/
public RegistrationHandle add(final T item) {
return add(Providers.of(item));
}
/**
* Add one new element to the set.
*
* @param item the item to add to the collection. Must not be null.
* @return handle to remove the item at a later point in time.
*/
public RegistrationHandle add(final Provider item) {
final AtomicReference> ref = new AtomicReference<>(item);
items.add(ref);
return new RegistrationHandle() {
@Override
public void remove() {
if (ref.compareAndSet(item, null)) {
items.remove(ref);
}
}
};
}
/**
* Add one new element that may be hot-replaceable in the future.
*
* @param key unique description from the item's Guice binding. This can be later obtained from
* the registration handle to facilitate matching with the new equivalent instance during a
* hot reload.
* @param item the item to add to the collection right now. Must not be null.
* @return a handle that can remove this item later, or hot-swap the item without it ever leaving
* the collection.
*/
public ReloadableRegistrationHandle add(Key key, Provider item) {
AtomicReference> ref = new AtomicReference<>(item);
items.add(ref);
return new ReloadableHandle(ref, key, item);
}
private class ReloadableHandle implements ReloadableRegistrationHandle {
private final AtomicReference> ref;
private final Key key;
private final Provider item;
ReloadableHandle(AtomicReference> ref, Key key, Provider item) {
this.ref = ref;
this.key = key;
this.item = item;
}
@Override
public void remove() {
if (ref.compareAndSet(item, null)) {
items.remove(ref);
}
}
@Override
public Key getKey() {
return key;
}
@Override
public ReloadableHandle replace(Key newKey, Provider newItem) {
if (ref.compareAndSet(item, newItem)) {
return new ReloadableHandle(ref, newKey, newItem);
}
return null;
}
}
}