com.carlomicieli.jtrains.infrastructure.web.CompletableFutureReturnValueHandler.java Source code

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Here is the source code for com.carlomicieli.jtrains.infrastructure.web.CompletableFutureReturnValueHandler.java

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/*
 * Copyright 2014 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 com.carlomicieli.jtrains.infrastructure.web;

import org.springframework.core.MethodParameter;
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;

import java.util.concurrent.CompletableFuture;

/*
 * Heavily influenced by http://www.nurkiewicz.com/2013/03/deferredresult-asynchronous-processing.html
 */
public class CompletableFutureReturnValueHandler implements HandlerMethodReturnValueHandler {
    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        Class<?> paramType = returnType.getParameterType();
        return CompletableFuture.class.isAssignableFrom(paramType);
    }

    @Override
    public void handleReturnValue(Object returnValue, MethodParameter returnType,
            ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
        final DeferredResult<Object> deferredResult = new DeferredResult<>();
        final CompletableFuture<?> future = (CompletableFuture<?>) returnValue;
        final CompletableFuture<Object> completedFuture = future.handle((ret, err) -> {
            if (ret != null) {
                deferredResult.setResult(ret);
                return ret;
            } else {
                deferredResult.setErrorResult(err);
                return null;
            }
        });

        WebAsyncUtils.getAsyncManager(webRequest).startDeferredResultProcessing(deferredResult, mavContainer);
    }
}