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Elasticsearch subproject :server
/*
* 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.spi;
import org.elasticsearch.common.inject.Binder;
import org.elasticsearch.common.inject.Key;
import org.elasticsearch.common.inject.Provider;
import java.util.Objects;
/**
* A lookup of the provider for a type. Lookups are created explicitly in a module using
* {@link org.elasticsearch.common.inject.Binder#getProvider(Class) getProvider()} statements:
*
* Provider<PaymentService> paymentServiceProvider
* = getProvider(PaymentService.class);
*
* @author [email protected] (Jesse Wilson)
* @since 2.0
*/
public final class ProviderLookup implements Element {
// NOTE: this class is not part of guice and was added so the provider lookup's key can be accessible for tests
public static class ProviderImpl implements Provider {
private ProviderLookup lookup;
private ProviderImpl(ProviderLookup lookup) {
this.lookup = lookup;
}
@Override
public T get() {
if (lookup.delegate == null) {
throw new IllegalStateException( "This Provider cannot be used until the Injector has been created.");
}
return lookup.delegate.get();
}
@Override
public String toString() {
return "Provider<" + lookup.key.getTypeLiteral() + ">";
}
public Key getKey() {
return lookup.getKey();
}
}
private final Object source;
private final Key key;
private Provider delegate;
public ProviderLookup(Object source, Key key) {
this.source = Objects.requireNonNull(source, "source");
this.key = Objects.requireNonNull(key, "key");
}
@Override
public Object getSource() {
return source;
}
public Key getKey() {
return key;
}
@Override
public T acceptVisitor(ElementVisitor visitor) {
return visitor.visit(this);
}
/**
* Sets the actual provider.
*
* @throws IllegalStateException if the delegate is already set
*/
public void initializeDelegate(Provider delegate) {
if (this.delegate != null) {
throw new IllegalStateException("delegate already initialized");
}
this.delegate = Objects.requireNonNull(delegate, "delegate");
}
@Override
public void applyTo(Binder binder) {
initializeDelegate(binder.withSource(getSource()).getProvider(key));
}
/**
* Returns the delegate provider, or {@code null} if it has not yet been initialized. The delegate
* will be initialized when this element is processed, or otherwise used to create an injector.
*/
public Provider getDelegate() {
return delegate;
}
/**
* Returns the looked up provider. The result is not valid until this lookup has been initialized,
* which usually happens when the injector is created. The provider will throw an {@code
* IllegalStateException} if you try to use it beforehand.
*/
public Provider getProvider() {
return new ProviderImpl<>(this);
}
}