org.elasticsearch.common.inject.Scopes Maven / Gradle / Ivy
/*
* Copyright (C) 2006 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;
import org.elasticsearch.common.inject.internal.Errors;
import org.elasticsearch.common.inject.internal.InternalFactory;
import org.elasticsearch.common.inject.internal.Scoping;
import java.lang.annotation.Annotation;
import java.util.Locale;
/**
* Built-in scope implementations.
*
* @author [email protected] (Bob Lee)
*/
public class Scopes {
private Scopes() {
}
/**
* One instance per {@link Injector}. Also see {@code @}{@link Singleton}.
*/
public static final Scope SINGLETON = new Scope() {
@Override
public Provider scope(Key key, final Provider creator) {
return new Provider() {
private volatile T instance;
// DCL on a volatile is safe as of Java 5, which we obviously require.
@Override
@SuppressWarnings("DoubleCheckedLocking")
public T get() {
if (instance == null) {
/*
* Use a pretty coarse lock. We don't want to run into deadlocks
* when two threads try to load circularly-dependent objects.
* Maybe one of these days we will identify independent graphs of
* objects and offer to load them in parallel.
*/
synchronized (InjectorImpl.class) {
if (instance == null) {
instance = creator.get();
}
}
}
return instance;
}
@Override
public String toString() {
return String.format(Locale.ROOT, "%s[%s]", creator, SINGLETON);
}
};
}
@Override
public String toString() {
return "Scopes.SINGLETON";
}
};
/**
* No scope; the same as not applying any scope at all. Each time the
* Injector obtains an instance of an object with "no scope", it injects this
* instance then immediately forgets it. When the next request for the same
* binding arrives it will need to obtain the instance over again.
*
* This exists only in case a class has been annotated with a scope
* annotation such as {@link Singleton @Singleton}, and you need to override
* this to "no scope" in your binding.
*
* @since 2.0
*/
public static final Scope NO_SCOPE = new Scope() {
@Override
public Provider scope(Key key, Provider unscoped) {
return unscoped;
}
@Override
public String toString() {
return "Scopes.NO_SCOPE";
}
};
/**
* Scopes an internal factory.
*/
static InternalFactory scope(Key key, InjectorImpl injector,
InternalFactory creator, Scoping scoping) {
if (scoping.isNoScope()) {
return creator;
}
Scope scope = scoping.getScopeInstance();
// TODO: use diamond operator once JI-9019884 is fixed
Provider scoped
= scope.scope(key, new ProviderToInternalFactoryAdapter(injector, creator));
return new InternalFactoryToProviderAdapter<>(
Initializables.>of(scoped));
}
/**
* Replaces annotation scopes with instance scopes using the Injector's annotation-to-instance
* map. If the scope annotation has no corresponding instance, an error will be added and unscoped
* will be retuned.
*/
static Scoping makeInjectable(Scoping scoping, InjectorImpl injector, Errors errors) {
Class scopeAnnotation = scoping.getScopeAnnotation();
if (scopeAnnotation == null) {
return scoping;
}
Scope scope = injector.state.getScope(scopeAnnotation);
if (scope != null) {
return Scoping.forInstance(scope);
}
errors.scopeNotFound(scopeAnnotation);
return Scoping.UNSCOPED;
}
}