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 import java.util.List; 24 25 /** 26 * Listens for provisioning of objects. Useful for gathering timing information 27 * about provisioning, post-provision initialization, and more. 28 * 29 * @author sameb@google.com (Sam Berlin) 30 * @since 4.0 31 */ 32 public interface ProvisionListener { 33 34 /** 35 * Invoked by Guice when an object requires provisioning. Provisioning occurs 36 * when Guice locates and injects the dependencies for a binding. For types 37 * bound to a Provider, provisioning encapsulates the {@link Provider#get} 38 * method. For toInstance or constant bindings, provisioning encapsulates 39 * the injecting of {@literal @}{@code Inject}ed fields or methods. 40 * For other types, provisioning encapsulates the construction of the 41 * object. If a type is bound within a {@link Scope}, provisioning depends on 42 * the scope. Types bound in Singleton scope will only be provisioned once. 43 * Types bound in no scope will be provisioned every time they are injected. 44 * Other scopes define their own behavior for provisioning. 45 * <p> 46 * To perform the provision, call {@link ProvisionInvocation#provision()}. 47 * If you do not explicitly call provision, it will be automatically done after 48 * this method returns. It is an error to call provision more than once. 49 */ onProvision(ProvisionInvocation<T> provision)50 <T> void onProvision(ProvisionInvocation<T> provision); 51 52 /** 53 * Encapsulates a single act of provisioning. 54 * 55 * @since 4.0 56 */ 57 public abstract static class ProvisionInvocation<T> { 58 59 /** 60 * Returns the Binding this is provisioning. 61 * <p> 62 * You must not call {@link Provider#get()} on the provider returned by 63 * {@link Binding#getProvider}, otherwise you will get confusing error messages. 64 */ getBinding()65 public abstract Binding<T> getBinding(); 66 67 /** Performs the provision, returning the object provisioned. */ provision()68 public abstract T provision(); 69 70 /** Returns the dependency chain that led to this object being provisioned. */ getDependencyChain()71 public abstract List<DependencyAndSource> getDependencyChain(); 72 73 } 74 } 75