作为响应实体的Jersey-StreamingOutput

Question

@GET
@Path("xxxxx")
@Produces(BulkConstants.TEXT_XML_MEDIA_TYPE})   
public Response getFile() {

    FeedReturnStreamingOutput sout = new FeedReturnStreamingOutput();
    response = Response.ok(sout).build();
    return response;
}

class FeedReturnStreamingOutput implements StreamingOutput {

    public FeedReturnStreamingOutput()

    @Override
    public void write(OutputStream outputStream)  {
        //write into Output Stream
    }
}

问题是，尽管在调用FeedReturnStreamingOutput之前从资源发回响应，但Jersey客户端会等待FeedReturnStreamingOutput执行完成。

客户端代码：

Client client = Client.create();

ClientResponse response = webResource
    //headers
    .get(ClientResponse.class);

//The codes underneath executes after FeedReturnStreamingOutput is executed which undermines the necessity of streaming

OutputStream os = new FileOutputStream("c:\\test\\feedoutput5.txt");
System.out.println(new Date() + " : Reached point A");

if (response.getStatus() == 200) {
    System.out.println(new Date() + " : Reached point B");
    InputStream io = response.getEntityInputStream();

    byte[] buff = new byte[1024000];
    int count = 0;

    while ((count = io.read(buff, 0, buff.length)) != -1) {
        os.write(buff, 0, count);
    }

    os.close();
    io.close();

} else {
    System.out.println("Response code :" + response.getStatus());
}

System.out.println("Time taken -->> "+(System.currentTimeMillis()-startTime)+" ms");

Answer 1

问题在于缓冲OutputStream，Jersey用来缓冲实体以确定内容长度头。缓冲区的大小默认为8 KB。如果需要，可以禁用缓冲，或者只使用属性更改缓冲区的大小

serverproperties.outbound_content_length_buffer

一个整数值，定义用于缓冲服务器端响应实体的缓冲区大小，以便确定其大小并设置HTTP“Content-Length”标头的值。

默认值为8192。

这里有一个例子

@Path("streaming")
public class StreamingResource {

    @GET
    @Produces("application/octet-stream")
    public Response getStream() {
        return Response.ok(new FeedReturnStreamingOutput()).build();
    }

    public static class FeedReturnStreamingOutput implements StreamingOutput {

        @Override
        public void write(OutputStream output)
                throws IOException, WebApplicationException {
            try {
                for (int i = 0; i < 10; i++) {
                    output.write(String.format("Hello %d\n", i).getBytes());
                    output.flush();
                    TimeUnit.MILLISECONDS.sleep(500);
                }
            } catch (InterruptedException e) {  throw new RuntimeException(e); }
        }
    }
}

以下是未设置属性的结果

public class AppConfig extends ResourceConfig {
    public AppConfig() {
        ...
        property(ServerProperties.OUTBOUND_CONTENT_LENGTH_BUFFER, 0);
    }
}