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/*
* Copyright 2002-2016 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.HashMap;
import java.util.Map;
import java.util.concurrent.CompletionStage;
import java.util.function.BiFunction;
import org.springframework.core.MethodParameter;
import org.springframework.lang.UsesJava8;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
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.AsyncHandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;
/**
* Handler for return values of type {@link DeferredResult}, {@link ListenableFuture},
* {@link CompletionStage} and any other async type with a {@link #getAdapterMap()
* registered adapter}.
*
* @author Rossen Stoyanchev
* @since 3.2
*/
public class DeferredResultMethodReturnValueHandler implements AsyncHandlerMethodReturnValueHandler {
private final Map<Class<?>, DeferredResultAdapter> adapterMap;
public DeferredResultMethodReturnValueHandler() {
this.adapterMap = new HashMap<Class<?>, DeferredResultAdapter>(5);
this.adapterMap.put(DeferredResult.class, new SimpleDeferredResultAdapter());
this.adapterMap.put(ListenableFuture.class, new ListenableFutureAdapter());
if (ClassUtils.isPresent("java.util.concurrent.CompletionStage", getClass().getClassLoader())) {
this.adapterMap.put(CompletionStage.class, new CompletionStageAdapter());
}
}
/**
* Return the map with {@code DeferredResult} adapters.
* <p>By default the map contains adapters for {@code DeferredResult}, which
* simply downcasts, {@link ListenableFuture}, and {@link CompletionStage}.
* @return the map of adapters
*/
public Map<Class<?>, DeferredResultAdapter> getAdapterMap() {
return this.adapterMap;
}
private DeferredResultAdapter getAdapterFor(Class<?> type) {
for (Class<?> adapteeType : getAdapterMap().keySet()) {
if (adapteeType.isAssignableFrom(type)) {
return getAdapterMap().get(adapteeType);
}
}
return null;
}
@Override
public boolean supportsReturnType(MethodParameter returnType) {
return (getAdapterFor(returnType.getParameterType()) != null);
}
@Override
public boolean isAsyncReturnValue(Object returnValue, MethodParameter returnType) {
return (returnValue != null && (getAdapterFor(returnValue.getClass()) != null));
}
@Override
public void handleReturnValue(Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
if (returnValue == null) {
mavContainer.setRequestHandled(true);
return;
}
DeferredResultAdapter adapter = getAdapterFor(returnValue.getClass());
Assert.notNull(adapter);
DeferredResult<?> result = adapter.adaptToDeferredResult(returnValue);
WebAsyncUtils.getAsyncManager(webRequest).startDeferredResultProcessing(result, mavContainer);
}
/**
* Adapter for {@code DeferredResult} return values.
*/
private static class SimpleDeferredResultAdapter implements DeferredResultAdapter {
@Override
public DeferredResult<?> adaptToDeferredResult(Object returnValue) {
Assert.isInstanceOf(DeferredResult.class, returnValue);
return (DeferredResult<?>) returnValue;
}
}
/**
* Adapter for {@code ListenableFuture} return values.
*/
private static class ListenableFutureAdapter implements DeferredResultAdapter {
@Override
public DeferredResult<?> adaptToDeferredResult(Object returnValue) {
Assert.isInstanceOf(ListenableFuture.class, returnValue);
final DeferredResult<Object> result = new DeferredResult<Object>();
((ListenableFuture<?>) returnValue).addCallback(new ListenableFutureCallback<Object>() {
@Override
public void onSuccess(Object value) {
result.setResult(value);
}
@Override
public void onFailure(Throwable ex) {
result.setErrorResult(ex);
}
});
return result;
}
}
/**
* Adapter for {@code CompletionStage} return values.
*/
@UsesJava8
private static class CompletionStageAdapter implements DeferredResultAdapter {
@Override
public DeferredResult<?> adaptToDeferredResult(Object returnValue) {
Assert.isInstanceOf(CompletionStage.class, returnValue);
final DeferredResult<Object> result = new DeferredResult<Object>();
@SuppressWarnings("unchecked")
CompletionStage<?> future = (CompletionStage<?>) returnValue;
future.handle(new BiFunction<Object, Throwable, Object>() {
@Override
public Object apply(Object value, Throwable ex) {
if (ex != null) {
result.setErrorResult(ex);
}
else {
result.setResult(value);
}
return null;
}
});
return result;
}
}
}
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