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Java example source code file (ProvidesIntoOptional.java)

This example Java source code file (ProvidesIntoOptional.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

actual, annotation, default, documented, providesintooptional, retention, target, type

The ProvidesIntoOptional.java Java example source code

/**
 * Copyright (C) 2015 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.multibindings;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import com.google.inject.Module;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Annotates methods of a {@link Module} to add items to a {@link Multibinder}.
 * The method's return type and binding annotation determines what Optional this will
 * contribute to. For example,
 *
 * <pre>
 * {@literal @}ProvidesIntoOptional(DEFAULT)
 * {@literal @}Named("url")
 * String provideFooUrl(FooManager fm) { returm fm.getUrl(); }
 *
 * {@literal @}ProvidesIntoOptional(ACTUAL)
 * {@literal @}Named("url")
 * String provideBarUrl(BarManager bm) { return bm.getUrl(); }
 * </pre>
 *
 * will set the default value of {@code @Named("url") Optional<String>} to foo's URL,
 * and then override it to bar's URL.
 *
 * @author sameb@google.com (Sam Berlin)
 * @since 4.0
 */
@Documented
@Target(METHOD)
@Retention(RUNTIME)
public @interface ProvidesIntoOptional {
  /**
   * @since 4.0
   */
  enum Type {
    /** Corresponds to {@link OptionalBinder#setBinding}. */
    ACTUAL,

    /** Corresponds to {@link OptionalBinder#setDefault}. */
    DEFAULT
  }

  /** Specifies if the binding is for the actual or default value. */
  Type value();
}

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