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/*
* Copyright (C) 2008 Google Inc.
*
* 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 org.elasticsearch.common.inject.multibindings;
import org.elasticsearch.common.inject.Binder;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.inject.Key;
import org.elasticsearch.common.inject.Module;
import org.elasticsearch.common.inject.Provider;
import org.elasticsearch.common.inject.TypeLiteral;
import org.elasticsearch.common.inject.binder.LinkedBindingBuilder;
import org.elasticsearch.common.inject.multibindings.Multibinder.RealMultibinder;
import org.elasticsearch.common.inject.spi.ProviderWithDependencies;
import org.elasticsearch.common.inject.util.Types;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import static org.elasticsearch.common.inject.util.Types.newParameterizedType;
import static org.elasticsearch.common.inject.util.Types.newParameterizedTypeWithOwner;
/**
* An API to bind multiple map entries separately, only to later inject them as
* a complete map. MapBinder is intended for use in your application's module:
*
* public class SnacksModule extends AbstractModule {
* protected void configure() {
* MapBinder<String, Snack> mapbinder
* = MapBinder.newMapBinder(binder(), String.class, Snack.class);
* mapbinder.addBinding("twix").toInstance(new Twix());
* mapbinder.addBinding("snickers").toProvider(SnickersProvider.class);
* mapbinder.addBinding("skittles").to(Skittles.class);
* }
* }
*
* With this binding, a {@link Map}{@code } can now be
* injected:
*
* class SnackMachine {
* {@literal @}Inject
* public SnackMachine(Map<String, Snack> snacks) { ... }
* }
*
* In addition to binding {@code Map}, a mapbinder will also bind
* {@code Map>} for lazy value provision:
*
* class SnackMachine {
* {@literal @}Inject
* public SnackMachine(Map<String, Provider<Snack>> snackProviders) { ... }
* }
*
* Creating mapbindings from different modules is supported. For example, it
* is okay to have both {@code CandyModule} and {@code ChipsModule} both
* create their own {@code MapBinder}, and to each contribute
* bindings to the snacks map. When that map is injected, it will contain
* entries from both modules.
*
* Values are resolved at map injection time. If a value is bound to a
* provider, that provider's get method will be called each time the map is
* injected (unless the binding is also scoped, or a map of providers is injected).
*
* Annotations are used to create different maps of the same key/value
* type. Each distinct annotation gets its own independent map.
*
* Keys must be distinct. If the same key is bound more than
* once, map injection will fail.
*
* Keys must be non-null. {@code addBinding(null)} will
* throw an unchecked exception.
*
* Values must be non-null to use map injection. If any
* value is null, map injection will fail (although injecting a map of providers
* will not).
*
* @author [email protected] (David P. Baker)
*/
public abstract class MapBinder {
private MapBinder() {}
/**
* Returns a new mapbinder that collects entries of {@code keyType}/{@code valueType} in a
* {@link Map} that is itself bound with no binding annotation.
*/
public static MapBinder newMapBinder(Binder binder, Class keyType, Class valueType) {
TypeLiteral keyType1 = TypeLiteral.get(keyType);
TypeLiteral valueType1 = TypeLiteral.get(valueType);
binder = binder.skipSources(MapBinder.class, RealMapBinder.class);
return newMapBinder(
binder,
valueType1,
Key.get(mapOf(keyType1, valueType1)),
Key.get(mapOfProviderOf(keyType1, valueType1)),
Multibinder.newSetBinder(binder, entryOfProviderOf(keyType1, valueType1))
);
}
@SuppressWarnings("unchecked") // a map of is safely a Map
private static TypeLiteral> mapOf(TypeLiteral keyType, TypeLiteral valueType) {
return (TypeLiteral>) TypeLiteral.get(Types.mapOf(keyType.getType(), valueType.getType()));
}
@SuppressWarnings("unchecked") // a provider map is safely a Map>
private static TypeLiteral>> mapOfProviderOf(TypeLiteral keyType, TypeLiteral valueType) {
return (TypeLiteral>>) TypeLiteral.get(
Types.mapOf(keyType.getType(), newParameterizedType(Provider.class, valueType.getType()))
);
}
@SuppressWarnings("unchecked") // a provider entry is safely a Map.Entry>
private static TypeLiteral>> entryOfProviderOf(TypeLiteral keyType, TypeLiteral valueType) {
return (TypeLiteral>>) TypeLiteral.get(
newParameterizedTypeWithOwner(Map.class, Entry.class, keyType.getType(), Types.providerOf(valueType.getType()))
);
}
private static MapBinder newMapBinder(
Binder binder,
TypeLiteral valueType,
Key> mapKey,
Key>> providerMapKey,
Multibinder>> entrySetBinder
) {
RealMapBinder mapBinder = new RealMapBinder<>(binder, valueType, mapKey, providerMapKey, entrySetBinder);
binder.install(mapBinder);
return mapBinder;
}
/**
* Returns a binding builder used to add a new entry in the map. Each
* key must be distinct (and non-null). Bound providers will be evaluated each
* time the map is injected.
*
* It is an error to call this method without also calling one of the
* {@code to} methods on the returned binding builder.
*
* Scoping elements independently is supported. Use the {@code in} method
* to specify a binding scope.
*/
public abstract LinkedBindingBuilder addBinding(K key);
/**
* The actual mapbinder plays several roles:
*
* As a MapBinder, it acts as a factory for LinkedBindingBuilders for
* each of the map's values. It delegates to a {@link Multibinder} of
* entries (keys to value providers).
*
* As a Module, it installs the binding to the map itself, as well as to
* a corresponding map whose values are providers. It uses the entry set
* multibinder to construct the map and the provider map.
*
* As a module, this implements equals() and hashcode() in order to trick
* Guice into executing its configure() method only once. That makes it so
* that multiple mapbinders can be created for the same target map, but
* only one is bound. Since the list of bindings is retrieved from the
* injector itself (and not the mapbinder), each mapbinder has access to
* all contributions from all equivalent mapbinders.
*
* Rather than binding a single Map.Entry<K, V>, the map binder
* binds keys and values independently. This allows the values to be properly
* scoped.
*
* We use a subclass to hide 'implements Module' from the public API.
*/
public static final class RealMapBinder extends MapBinder implements Module {
private final TypeLiteral valueType;
private final Key> mapKey;
private final Key>> providerMapKey;
private final RealMultibinder>> entrySetBinder;
/* the target injector's binder. non-null until initialization, null afterwards */
private Binder binder;
private RealMapBinder(
Binder binder,
TypeLiteral valueType,
Key> mapKey,
Key>> providerMapKey,
Multibinder>> entrySetBinder
) {
this.valueType = valueType;
this.mapKey = mapKey;
this.providerMapKey = providerMapKey;
this.entrySetBinder = (RealMultibinder>>) entrySetBinder;
this.binder = binder;
}
/**
* This creates two bindings. One for the {@code Map.Entry>}
* and another for {@code V}.
*/
@Override
public LinkedBindingBuilder addBinding(K key) {
Multibinder.checkNotNull(key, "key");
Multibinder.checkConfiguration(isInitialized() == false, "MapBinder was already initialized");
Key valueKey = Key.get(valueType, new RealElement(RealMultibinder.getSetName()));
entrySetBinder.addBinding().toInstance(new MapEntry<>(key, binder.getProvider(valueKey)));
return binder.bind(valueKey);
}
public static class MapBinderProviderWithDependencies implements ProviderWithDependencies>> {
private Map> providerMap;
@SuppressWarnings("rawtypes") // code is silly stupid with generics
private final RealMapBinder binder;
private final Provider>>> provider;
@SuppressWarnings("rawtypes") // code is silly stupid with generics
MapBinderProviderWithDependencies(RealMapBinder binder, Provider>>> provider) {
this.binder = binder;
this.provider = provider;
}
@SuppressWarnings({ "unchecked", "unused" }) // code is silly stupid with generics
@Inject
public void initialize() {
binder.binder = null;
Map> providerMapMutable = new LinkedHashMap<>();
for (Entry> entry : provider.get()) {
Multibinder.checkConfiguration(
providerMapMutable.put(entry.getKey(), entry.getValue()) == null,
"Map injection failed due to duplicated key \"%s\"",
entry.getKey()
);
}
providerMap = Collections.unmodifiableMap(providerMapMutable);
}
@Override
public Map> get() {
return providerMap;
}
}
@Override
@SuppressWarnings({ "rawtypes", "unchecked" }) // code is silly stupid with generics
public void configure(Binder binder) {
Multibinder.checkConfiguration(isInitialized() == false, "MapBinder was already initialized");
// binds a Map> from a collection of Map>
final Provider>>> entrySetProvider = binder.getProvider(entrySetBinder.getSetKey());
binder.bind(providerMapKey).toProvider(new MapBinderProviderWithDependencies(RealMapBinder.this, entrySetProvider));
final Provider>> mapProvider = binder.getProvider(providerMapKey);
binder.bind(mapKey).toProvider((ProviderWithDependencies>) () -> {
Map map = new LinkedHashMap<>();
for (Entry> entry : mapProvider.get().entrySet()) {
V value = entry.getValue().get();
K key = entry.getKey();
Multibinder.checkConfiguration(value != null, "Map injection failed due to null value for key \"%s\"", key);
map.put(key, value);
}
return Collections.unmodifiableMap(map);
});
}
private boolean isInitialized() {
return binder == null;
}
@Override
public boolean equals(Object o) {
return o instanceof RealMapBinder && ((RealMapBinder) o).mapKey.equals(mapKey);
}
@Override
public int hashCode() {
return mapKey.hashCode();
}
private static final class MapEntry implements Map.Entry {
private final K key;
private final V value;
private MapEntry(K key, V value) {
this.key = key;
this.value = value;
}
@Override
public K getKey() {
return key;
}
@Override
public V getValue() {
return value;
}
@Override
public V setValue(V value) {
throw new UnsupportedOperationException();
}
@Override
public boolean equals(Object obj) {
return obj instanceof Map.Entry
&& key.equals(((Map.Entry) obj).getKey())
&& value.equals(((Map.Entry) obj).getValue());
}
@Override
public int hashCode() {
return 127 * ("key".hashCode() ^ key.hashCode()) + 127 * ("value".hashCode() ^ value.hashCode());
}
@Override
public String toString() {
return "MapEntry(" + key + ", " + value + ")";
}
}
}
}