https://github.com/google/guice/guice: Guice is a lightweight dependency injection framework for Java 6 and above (Google, Inc.) 
/*
 * Copyright (C) 2010 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 java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import com.google.inject.Injector;
import com.google.inject.Stage;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;


Instructs an Injector running in Stage.TOOL that a method should be injected. This is typically useful for for extensions to Guice that perform additional validation in an injected method or field. This only applies to objects that are already constructed when bindings are created (ie., something bound using toProvider, toInstance, or requestInjection. 
Author:sberlin@gmail.com (Sam Berlin)
Since:3.0
/**
 * Instructs an {@link Injector} running in {@link Stage#TOOL} that a method should be injected.
 * This is typically useful for for extensions to Guice that perform additional validation in an
 * injected method or field. This only applies to objects that are already constructed when bindings
 * are created (ie., something bound using {@link
 * com.google.inject.binder.LinkedBindingBuilder#toProvider toProvider}, {@link
 * com.google.inject.binder.LinkedBindingBuilder#toInstance toInstance}, or {@link
 * com.google.inject.Binder#requestInjection requestInjection}.
 *
 * @author sberlin@gmail.com (Sam Berlin)
 * @since 3.0
 */
@Target({METHOD})
@Retention(RUNTIME)
@Documented
public @interface Toolable {}