org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBodyReturnValueHandler.java Source code

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Here is the source code for org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBodyReturnValueHandler.java

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/*
 * Copyright 2002-2015 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.io.OutputStream;
import java.util.concurrent.Callable;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.http.ResponseEntity;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.http.server.ServletServerHttpResponse;
import org.springframework.util.Assert;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.async.WebAsyncUtils;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.method.support.ModelAndViewContainer;

/**
 * Supports return values of type
 * {@link org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody}
 * and also {@code ResponseEntity<StreamingResponseBody>}.
 *
 * @author Rossen Stoyanchev
 * @since 4.2
 */
public class StreamingResponseBodyReturnValueHandler implements HandlerMethodReturnValueHandler {

    private static final Log logger = LogFactory.getLog(StreamingResponseBodyReturnValueHandler.class);

    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        if (StreamingResponseBody.class.isAssignableFrom(returnType.getParameterType())) {
            return true;
        } else if (ResponseEntity.class.isAssignableFrom(returnType.getParameterType())) {
            Class<?> bodyType = ResolvableType.forMethodParameter(returnType).getGeneric(0).resolve();
            return (bodyType != null && StreamingResponseBody.class.isAssignableFrom(bodyType));
        }
        return false;
    }

    @Override
    public void handleReturnValue(Object returnValue, MethodParameter returnType,
            ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {

        if (returnValue == null) {
            mavContainer.setRequestHandled(true);
            return;
        }

        HttpServletResponse response = webRequest.getNativeResponse(HttpServletResponse.class);
        ServerHttpResponse outputMessage = new ServletServerHttpResponse(response);

        if (ResponseEntity.class.isAssignableFrom(returnValue.getClass())) {
            ResponseEntity<?> responseEntity = (ResponseEntity<?>) returnValue;
            outputMessage.setStatusCode(responseEntity.getStatusCode());
            outputMessage.getHeaders().putAll(responseEntity.getHeaders());

            returnValue = responseEntity.getBody();
            if (returnValue == null) {
                mavContainer.setRequestHandled(true);
                return;
            }
        }

        Assert.isInstanceOf(StreamingResponseBody.class, returnValue);
        StreamingResponseBody streamingBody = (StreamingResponseBody) returnValue;

        Callable<Void> callable = new StreamingResponseBodyTask(outputMessage.getBody(), streamingBody);
        WebAsyncUtils.getAsyncManager(webRequest).startCallableProcessing(callable, mavContainer);
    }

    private static class StreamingResponseBodyTask implements Callable<Void> {

        private final OutputStream outputStream;

        private final StreamingResponseBody streamingBody;

        public StreamingResponseBodyTask(OutputStream outputStream, StreamingResponseBody streamingBody) {
            this.outputStream = outputStream;
            this.streamingBody = streamingBody;
        }

        @Override
        public Void call() throws Exception {
            this.streamingBody.writeTo(this.outputStream);
            return null;
        }
    }

}