经过一番调查，我发现我需要 Box API 的 Content-Type: multipart/form-data 并适当地构建请求。我使用的 Google HTTP 客户端版本不可能，所以我自己实现了 MultipartFormDataContent 类，它非常适合库。这是该课程的完整列表。也许它可以包含在库中。
/*
* Copyright (c) 2013 Google Inc.
*
* 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.
*/
/**
* This is a modification of com.google.api.client.http.MultipartContent from
* Google HTTP Client library to support multipart/form-data requests.
*
* The original author is Yaniv Inbar.
*/
public class MultipartFormDataContent extends AbstractHttpContent {
private static final String NEWLINE = "\r\n";
private static final String TWO_DASHES = "--";
private ArrayList<Part> parts = new ArrayList<Part>();
public MultipartFormDataContent() {
super(new HttpMediaType("multipart/form-data").setParameter("boundary", "__END_OF_PART__"));
}
@Override
public void writeTo(OutputStream out) throws IOException {
Writer writer = new OutputStreamWriter(out, getCharset());
String boundary = getBoundary();
for (Part part : parts) {
HttpHeaders headers = new HttpHeaders().setAcceptEncoding(null);
if (part.headers != null) {
headers.fromHttpHeaders(part.headers);
}
headers.setContentEncoding(null)
.setUserAgent(null)
.setContentType(null)
.setContentLength(null);
// analyze the content
HttpContent content = part.content;
StreamingContent streamingContent = null;
String contentDisposition = String.format("form-data; name=\"%s\"", part.name);
if (part.filename != null) {
headers.setContentType(content.getType());
contentDisposition += String.format("; filename=\"%s\"", part.filename);
}
headers.set("Content-Disposition", contentDisposition);
HttpEncoding encoding = part.encoding;
if (encoding == null) {
streamingContent = content;
} else {
headers.setContentEncoding(encoding.getName());
streamingContent = new HttpEncodingStreamingContent(content, encoding);
}
// write separator
writer.write(TWO_DASHES);
writer.write(boundary);
writer.write(NEWLINE);
// write headers
HttpHeaders.serializeHeadersForMultipartRequests(headers, null, null, writer);
// write content
if (streamingContent != null) {
writer.write(NEWLINE);
writer.flush();
streamingContent.writeTo(out);
writer.write(NEWLINE);
}
}
// write end separator
writer.write(TWO_DASHES);
writer.write(boundary);
writer.write(TWO_DASHES);
writer.write(NEWLINE);
writer.flush();
}
@Override
public boolean retrySupported() {
for (Part part : parts) {
if (!part.content.retrySupported()) {
return false;
}
}
return true;
}
@Override
public MultipartFormDataContent setMediaType(HttpMediaType mediaType) {
super.setMediaType(mediaType);
return this;
}
/**
* Adds an HTTP multipart part.
*
* <p>
* Overriding is only supported for the purpose of calling the super
* implementation and changing the return type, but nothing else.
* </p>
*/
public MultipartFormDataContent addPart(Part part) {
parts.add(Preconditions.checkNotNull(part));
return this;
}
/**
* Sets the boundary string to use.
*
* <p>
* Defaults to {@code "END_OF_PART"}.
* </p>
*
* <p>
* Overriding is only supported for the purpose of calling the super
* implementation and changing the return type, but nothing else.
* </p>
*/
public MultipartFormDataContent setBoundary(String boundary) {
getMediaType().setParameter("boundary", Preconditions.checkNotNull(boundary));
return this;
}
/**
* Single part of a multi-part request.
*
* <p>
* Implementation is not thread-safe.
* </p>
*/
public static final class Part {
private String name;
private String filename;
private HttpContent content;
private HttpHeaders headers;
private HttpEncoding encoding;
public Part setContent(HttpContent content) {
this.content = content;
return this;
}
public Part setHeaders(HttpHeaders headers) {
this.headers = headers;
return this;
}
public Part setEncoding(HttpEncoding encoding) {
this.encoding = encoding;
return this;
}
public Part setName(String name) {
this.name = name;
return this;
}
public Part setFilename(String filename) {
this.filename = filename;
return this;
}
}
}