spring AsyncHandlerMethodReturnValueHandler 源码

spring AsyncHandlerMethodReturnValueHandler 代码

文件路径：/spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/AsyncHandlerMethodReturnValueHandler.java

/*
 * Copyright 2002-2022 the original author or authors.
 *
 * 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
 *
 *      https://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 org.springframework.messaging.handler.invocation;

import java.util.concurrent.CompletableFuture;

import org.springframework.core.MethodParameter;
import org.springframework.lang.Nullable;

/**
 * An extension of {@link HandlerMethodReturnValueHandler} for handling async,
 * Future-like return value types that support success and error callbacks.
 * Essentially anything that can be adapted to a
 * {@link org.springframework.util.concurrent.ListenableFuture ListenableFuture}.
 *
 * <p>Implementations should consider extending the convenient base class
 * {@link AbstractAsyncReturnValueHandler}.
 *
 * @author Rossen Stoyanchev
 * @since 4.2
 * @see AbstractAsyncReturnValueHandler
 */
public interface AsyncHandlerMethodReturnValueHandler extends HandlerMethodReturnValueHandler {

	/**
	 * Whether the return value represents an asynchronous, Future-like type
	 * with success and error callbacks. If this method returns {@code true},
	 * then {@link #toCompletableFuture} is invoked next. If it returns
	 * {@code false}, then {@link #handleReturnValue} is called.
	 * <p><strong>Note:</strong> this method will only be invoked after
	 * {@link #supportsReturnType(org.springframework.core.MethodParameter)}
	 * is called and it returns {@code true}.
	 * @param returnValue the value returned from the handler method
	 * @param returnType the type of the return value
	 * @return {@code true} if the return value type represents an async value
	 */
	boolean isAsyncReturnValue(Object returnValue, MethodParameter returnType);

	/**
	 * Adapt the asynchronous return value to a
	 * {@link org.springframework.util.concurrent.ListenableFuture ListenableFuture}.
	 * <p>Implementations should consider returning an instance of
	 * {@link org.springframework.util.concurrent.SettableListenableFuture
	 * SettableListenableFuture}. Return value handling will then continue when
	 * the ListenableFuture is completed with either success or error.
	 * <p><strong>Note:</strong> this method will only be invoked after
	 * {@link #supportsReturnType(org.springframework.core.MethodParameter)}
	 * is called and it returns {@code true}.
	 * @param returnValue the value returned from the handler method
	 * @param returnType the type of the return value
	 * @return the resulting ListenableFuture, or {@code null} in which case
	 * no further handling will be performed
	 * @deprecated as of 6.0, in favor of
	 * {@link #toCompletableFuture(Object, MethodParameter)}
	 */
	@Deprecated
	@Nullable
	default org.springframework.util.concurrent.ListenableFuture<?> toListenableFuture(
			Object returnValue, MethodParameter returnType) {
		CompletableFuture<?> result = toCompletableFuture(returnValue, returnType);
		return (result != null ?
				new org.springframework.util.concurrent.CompletableToListenableFutureAdapter<>(result) :
				null);
	}

	/**
	 * Adapt the asynchronous return value to a {@link CompletableFuture}.
	 * <p>Return value handling will then continue when
	 * the CompletableFuture is completed with either success or error.
	 * <p><strong>Note:</strong> this method will only be invoked after
	 * {@link #supportsReturnType(org.springframework.core.MethodParameter)}
	 * is called and it returns {@code true}.
	 * @param returnValue the value returned from the handler method
	 * @param returnType the type of the return value
	 * @return the resulting CompletableFuture, or {@code null} in which case
	 * no further handling will be performed
	 * @since 6.0
	 */
	@Nullable
	CompletableFuture<?> toCompletableFuture(Object returnValue, MethodParameter returnType);

}

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