1 /* 2 * Copyright (C) 2011 Google Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not 5 * use this file except in compliance with the License. You may obtain a copy of 6 * the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 13 * License for the specific language governing permissions and limitations under 14 * the License. 15 */ 16 17 package com.google.inject.spi; 18 19 import com.google.inject.Binding; 20 import com.google.inject.Provider; 21 import com.google.inject.Scope; 22 23 /** 24 * Listens for provisioning of objects. Useful for gathering timing information about provisioning, 25 * post-provision initialization, and more. 26 * 27 * @author sameb@google.com (Sam Berlin) 28 * @since 4.0 29 */ 30 public interface ProvisionListener { 31 32 /** 33 * Invoked by Guice when an object requires provisioning. Provisioning occurs when Guice locates 34 * and injects the dependencies for a binding. For types bound to a Provider, provisioning 35 * encapsulates the {@link Provider#get} method. For toInstance or constant bindings, provisioning 36 * encapsulates the injecting of {@literal @}{@code Inject}ed fields or methods. For other types, 37 * provisioning encapsulates the construction of the object. If a type is bound within a {@link 38 * Scope}, provisioning depends on the scope. Types bound in Singleton scope will only be 39 * provisioned once. Types bound in no scope will be provisioned every time they are injected. 40 * Other scopes define their own behavior for provisioning. 41 * 42 * <p>To perform the provision, call {@link ProvisionInvocation#provision()}. If you do not 43 * explicitly call provision, it will be automatically done after this method returns. It is an 44 * error to call provision more than once. 45 */ onProvision(ProvisionInvocation<T> provision)46 <T> void onProvision(ProvisionInvocation<T> provision); 47 48 /** 49 * Encapsulates a single act of provisioning. 50 * 51 * @since 4.0 52 */ 53 public abstract static class ProvisionInvocation<T> { 54 55 /** 56 * Returns the Binding this is provisioning. 57 * 58 * <p>You must not call {@link Provider#get()} on the provider returned by {@link 59 * Binding#getProvider}, otherwise you will get confusing error messages. 60 */ getBinding()61 public abstract Binding<T> getBinding(); 62 63 /** Performs the provision, returning the object provisioned. */ provision()64 public abstract T provision(); 65 66 /** 67 * Returns the dependency chain that led to this object being provisioned. 68 * 69 * @deprecated This method is planned for removal in Guice 4.4. Some use cases can be replaced 70 * by inferring the current chain via ThreadLocals in the listener, other use cases can use 71 * the static dependency graph. For example, 72 * <pre>{@code 73 * bindListener(Matchers.any(), new MyListener()); 74 * ... 75 * 76 * private static final class MyListener implements ProvisionListener { 77 * private final ThreadLocal<ArrayDeque<Binding<?>>> bindingStack = 78 * new ThreadLocal<ArrayDeque<Binding<?>>>() { 79 * {@literal @}Override protected ArrayDeque<Binding<?>> initialValue() { 80 * return new ArrayDeque<>(); 81 * } 82 * }; 83 * {@literal @}Override public <T> void onProvision(ProvisionInvocation<T> invocation) { 84 * bindingStack.get().push(invocation.getBinding()); 85 * try { 86 * invocation.provision(); 87 * } finally { 88 * bindingStack.get().pop(); 89 * } 90 * // Inspect the binding stack... 91 * } 92 * } 93 * 94 * }<pre> 95 * 96 * In this example the bindingStack thread local will contain a data structure that is very 97 * similar to the data returned by this list. The main differences are that linked keys are 98 * not in the stack, but such edges do exist in the static dependency graph (inspectable via 99 * {@link HasDependencies#getDependencies()}), so you could infer some of the missing edges.. 100 */ 101 @Deprecated getDependencyChain()102 public abstract java.util.List<DependencyAndSource> getDependencyChain(); 103 104 } 105 } 106