/*
* Copyright 2002-2017 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
*
* 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 org.springframework.web.servlet.mvc.method.annotation;
import java.util.concurrent.CompletionStage;
import java.util.function.BiFunction;
import org.springframework.core.MethodParameter;
import org.springframework.util.concurrent.ListenableFuture;
import org.springframework.util.concurrent.ListenableFutureCallback;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.DeferredResult;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
/**
* Handler for return values of type {@link DeferredResult},
* {@link ListenableFuture}, and {@link CompletionStage}.
*
* @author Rossen Stoyanchev
* @since 3.2
*/
public class DeferredResultMethodReturnValueHandler implements HandlerMethodReturnValueHandler {
@Override
public boolean supportsReturnType(MethodParameter returnType) {
Class<?> type = returnType.getParameterType();
return DeferredResult.class.isAssignableFrom(type) ||
ListenableFuture.class.isAssignableFrom(type) ||
CompletionStage.class.isAssignableFrom(type);
}
@Override
public void handleReturnValue(Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
if (returnValue == null) {
mavContainer.setRequestHandled(true);
return;
}
DeferredResult<?> result;
if (returnValue instanceof DeferredResult) {
result = (DeferredResult<?>) returnValue;
}
else if (returnValue instanceof ListenableFuture) {
result = adaptListenableFuture((ListenableFuture<?>) returnValue);
}
else if (returnValue instanceof CompletionStage) {
result = adaptCompletionStage((CompletionStage<?>) returnValue);
}
else {
// Should not happen...
throw new IllegalStateException("Unexpected return value type: " + returnValue);
}
WebAsyncUtils.getAsyncManager(webRequest).startDeferredResultProcessing(result, mavContainer);
}
private DeferredResult<Object> adaptListenableFuture(ListenableFuture<?> future) {
DeferredResult<Object> result = new DeferredResult<>();
future.addCallback(new ListenableFutureCallback<Object>() {
@Override
public void onSuccess(Object value) {
result.setResult(value);
}
@Override
public void onFailure(Throwable ex) {
result.setErrorResult(ex);
}
});
return result;
}
private DeferredResult<Object> adaptCompletionStage(CompletionStage<?> future) {
DeferredResult<Object> result = new DeferredResult<>();
future.handle((BiFunction<Object, Throwable, Object>) (value, ex) -> {
if (ex != null) {
result.setErrorResult(ex);
}
else {
result.setResult(value);
}
return null;
});
return result;
}
}