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/*
* Copyright (C) 2011 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 com.google.inject.Binding;
import com.google.inject.Provider;
import com.google.inject.Scope;
/**
* Listens for provisioning of objects. Useful for gathering timing information about provisioning,
* post-provision initialization, and more.
*
* @author sameb@google.com (Sam Berlin)
* @since 4.0
*/
public interface ProvisionListener {
/**
* Invoked by Guice when an object requires provisioning. Provisioning occurs when Guice locates
* and injects the dependencies for a binding. For types bound to a Provider, provisioning
* encapsulates the {@link Provider#get} method. For toInstance or constant bindings, provisioning
* encapsulates the injecting of {@literal @}{@code Inject}ed fields or methods. For other types,
* provisioning encapsulates the construction of the object. If a type is bound within a {@link
* Scope}, provisioning depends on the scope. Types bound in Singleton scope will only be
* provisioned once. Types bound in no scope will be provisioned every time they are injected.
* Other scopes define their own behavior for provisioning.
*
* <p>To perform the provision, call {@link ProvisionInvocation#provision()}. If you do not
* explicitly call provision, it will be automatically done after this method returns. It is an
* error to call provision more than once.
*/
<T> void onProvision(ProvisionInvocation<T> provision);
/**
* Encapsulates a single act of provisioning.
*
* @since 4.0
*/
public abstract static class ProvisionInvocation<T> {
/**
* Returns the Binding this is provisioning.
*
* <p>You must not call {@link Provider#get()} on the provider returned by {@link
* Binding#getProvider}, otherwise you will get confusing error messages.
*/
public abstract Binding<T> getBinding();
/** Performs the provision, returning the object provisioned. */
public abstract T provision();
/**
* Returns the dependency chain that led to this object being provisioned.
*
* @deprecated This method is planned for removal in Guice 4.4. Some use cases can be replaced
* by inferring the current chain via ThreadLocals in the listener, other use cases can use
* the static dependency graph. For example,
* <pre>{@code
* bindListener(Matchers.any(), new MyListener());
* ...
*
* private static final class MyListener implements ProvisionListener {
* private final ThreadLocal<ArrayDeque<Binding<?>>> bindingStack =
* new ThreadLocal<ArrayDeque<Binding<?>>>() {
* {@literal @}Override protected ArrayDeque<Binding<?>> initialValue() {
* return new ArrayDeque<>();
* }
* };
* {@literal @}Override public <T> void onProvision(ProvisionInvocation<T> invocation) {
* bindingStack.get().push(invocation.getBinding());
* try {
* invocation.provision();
* } finally {
* bindingStack.get().pop();
* }
* // Inspect the binding stack...
* }
* }
*
* }<pre>
*
* In this example the bindingStack thread local will contain a data structure that is very
* similar to the data returned by this list. The main differences are that linked keys are
* not in the stack, but such edges do exist in the static dependency graph (inspectable via
* {@link HasDependencies#getDependencies()}), so you could infer some of the missing edges..
*/
@Deprecated
public abstract java.util.List<DependencyAndSource> getDependencyChain();
}
}
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