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/*
* Copyright (C) 2009 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 com.google.inject.spi;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.inject.Binder;
import com.google.inject.MembersInjector;
import com.google.inject.TypeLiteral;
/**
* A lookup of the members injector for a type. Lookups are created explicitly in a module using
* {@link com.google.inject.Binder#getMembersInjector(Class) getMembersInjector()} statements:
*
* <pre>
* MembersInjector<PaymentService> membersInjector
* = getMembersInjector(PaymentService.class);</pre>
*
* @author crazybob@google.com (Bob Lee)
* @since 2.0
*/
public final class MembersInjectorLookup<T> implements Element {
private final Object source;
private final TypeLiteral<T> type;
private MembersInjector<T> delegate;
public MembersInjectorLookup(Object source, TypeLiteral<T> type) {
this.source = checkNotNull(source, "source");
this.type = checkNotNull(type, "type");
}
@Override
public Object getSource() {
return source;
}
/** Gets the type containing the members to be injected. */
public TypeLiteral<T> getType() {
return type;
}
@Override
public <T> T acceptVisitor(ElementVisitor<T> visitor) {
return visitor.visit(this);
}
/**
* Sets the actual members injector.
*
* @throws IllegalStateException if the delegate is already set
*/
public void initializeDelegate(MembersInjector<T> delegate) {
checkState(this.delegate == null, "delegate already initialized");
this.delegate = checkNotNull(delegate, "delegate");
}
@Override
public void applyTo(Binder binder) {
initializeDelegate(binder.withSource(getSource()).getMembersInjector(type));
}
/**
* Returns the delegate members injector, 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 MembersInjector<T> getDelegate() {
return delegate;
}
/**
* Returns the looked up members injector. The result is not valid until this lookup has been
* initialized, which usually happens when the injector is created. The members injector will
* throw an {@code IllegalStateException} if you try to use it beforehand.
*/
public MembersInjector<T> getMembersInjector() {
return new MembersInjector<T>() {
@Override
public void injectMembers(T instance) {
MembersInjector<T> local = delegate;
if (local == null) {
throw new IllegalStateException(
"This MembersInjector cannot be used until the Injector has been created.");
}
local.injectMembers(instance);
}
@Override
public String toString() {
return "MembersInjector<" + type + ">";
}
};
}
}
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