在Jersey JAX-RS服务器中返回大对象时如何设置Content-Length [英] How do I set Content-Length when returning large objects in Jersey JAX-RS server

问题描述

有时我想返回一个大的(几个MB)二进制对象作为JAX-RS资源方法的响应.我知道对象的大小，并且我希望在响应中设置Content-Length标头，并且我不希望使用分块传输编码.

I sometimes want to return a large (several MB) binary object as a response from a JAX-RS resource method. I know the size of the object, and I want the Content-Length header to be set on the response, and I don't want chunked transfer encoding to be used.

在Jersey 1.x中，我使用自定义的MessageBodyWriter解决了这个问题:

In Jersey 1.x, I solved this with a custom MessageBodyWriter:

public class Blob {
  public InputStream stream;
  public long length;    
}

@Provider
public class BlobWriter extends MessageBodyWriter<Blob> {

  public boolean isWriteable(Class<?> type, Type genericType,
                               Annotation[] annotations, MediaType mediaType) {
    return Blob.class.isAssignableFrom(type);
  }

  public long getSize(T t, Class<?> type, Type genericType, Annotation[] annotations,
                        MediaType mediaType) {
    return t.length;
  }

  public void writeTo(T t, Class<?> type, Type genericType, Annotation[] annotations,
                      MediaType mediaType,
                      MultivaluedMap<String, Object> httpHeaders,
                      OutputStream entityStream)
            throws java.io.IOException {
    org.glassfish.jersey.message.internal.ReaderWriter.writeTo(t.stream, entityStream);
  }
}

但是当我升级到Jersey 2.x时，此操作停止了，因为JAX-RS/Jersey 2不再关心MessageBodyWriter.getSize()了.我该如何使用Jersey 2做到这一点?

But this stopped working when I upgraded to Jersey 2.x, since JAX-RS/Jersey 2 does not care about MessageBodyWriter.getSize() anymore. How can I accomplish this with Jersey 2?

推荐答案

似乎可以使用提供的httpHeaders从MessageBodyWriter.writeTo()设置Content-Length标头:

It seems to be possible to set the Content-Length header from MessageBodyWriter.writeTo() using the supplied httpHeaders:

  public void writeTo(T t, Class<?> type, Type genericType, Annotation[] annotations,
                      MediaType mediaType,
                      MultivaluedMap<String, Object> httpHeaders,
                      OutputStream entityStream)
            throws java.io.IOException {
    httpHeaders.addFirst(HttpHeaders.CONTENT_LENGTH, t.length.toString);
    org.glassfish.jersey.message.internal.ReaderWriter.writeTo(t.stream, entityStream);
  }

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