问题

我正在学习最新的apache hc异步客户端的示例。响应流式传输功能非常有用，正是我需要的（比如在每个数据块到达时计算延迟，这在CloseableHttpClient中似乎缺失）。

但是在设置请求体方面遇到了问题。

以AsyncClientHttpExchangeStreaming为例，我可以运行此示例，但是当尝试添加一些请求体时，比如以下内容，我发现它不起作用（httpbin的响应非常清楚，data或json字段为空）。

      String bodyString = "{\"k\":\"v\"}";
      final SimpleHttpRequest request = SimpleRequestBuilder
        .post()
        .setHttpHost(target)
        .setPath("/post")
        .setBody(bodyString, ContentType.APPLICATION_JSON)
        .build();

然后我注意到client.execute(new BasicRequestProducer(request, null),并尝试将null替换为new BasicAsyncEntityProducer(bodyString, ContentType.APPLICATION_JSON);，这次httpbin告诉我它接收到了bodyString（这个解决方法是否正确以及为什么需要？）。

当我尝试像上面的解决方法一样发布多部分表单时，服务器报告错误，如'content-length missing'或'malformed request'：

    final StringBody inputBody = new StringBody(inputJson, ContentType.APPLICATION_JSON);
    final StringBody parametersBody = new StringBody(parametersJson, ContentType.APPLICATION_JSON);

    final HttpEntity reqEntity = MultipartEntityBuilder.create()
        .addPart("Input", inputBody)
        .addPart("Parameters", parametersBody)
        .build();
    //上面的reqEntity可以在同步客户端中成功请求我的服务器
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    reqEntity.writeTo(baos);
    byte[] bytes = baos.toByteArray();
    BasicAsyncEntityProducer multiPartProducer = new BasicAsyncEntityProducer(
        bytes,
        ContentType.MULTIPART_FORM_DATA
    );

我搜索了很多，有人说MultipartEntityBuilder创建的HttpEntity不能与异步客户端一起使用。我感到非常失望和沮丧。有人能否建议在apache hc中正确的方法，或者是否有其他库可以代替？

      String bodyString = "{\"k\":\"v\"}";
      final SimpleHttpRequest request = SimpleRequestBuilder
        .post()
        .setHttpHost(target)
        .setPath("/post")
        .setBody(bodyString, ContentType.APPLICATION_JSON)
        .build();

    final StringBody inputBody = new StringBody(inputJson, ContentType.APPLICATION_JSON);
    final StringBody parametersBody = new StringBody(parametersJson, ContentType.APPLICATION_JSON);

    final HttpEntity reqEntity = MultipartEntityBuilder.create()
        .addPart("Input", inputBody)
        .addPart("Parameters", parametersBody)
        .build();
    //above reqEntity can successful request my server in sync client
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    reqEntity.writeTo(baos);
    byte[] bytes = baos.toByteArray();
    BasicAsyncEntityProducer multiPartProducer = new BasicAsyncEntityProducer(
        bytes,
        ContentType.MULTIPART_FORM_DATA
    );

答案1

得分: 0

"Found solution and answer myself, hope helpful for some newcomers like me. Still welcome more elgant solution.

• Cause of the issue
  HttpEntity created by MultipartEntityBuilder is wrapped into BasicAsyncEntityProducer as bytes, library sends the bytes as they are, and http post header missing boundary information.

• Solution
  Get the Content-Type header including the boundery info then update it into request headers.

//get the `Content-Type` header including the boundery info
//value is like:
//Content-Type: multipart/form-data; charset=ISO-8859-1; boundary=fLC0K1nKdSI-Q9vzFpU2WleMTXyWbOBp6
String contentType = reqEntity.getContentType();
final SimpleHttpRequest request = SimpleRequestBuilder
//...omit other methods
.setHeader("Content-Type", contentType)
```"

<details>
<summary>英文:</summary>

  Found solution and answer myself, hope helpful for some newcomers like me.
  Still welcome more elgant solution.

 - Cause of the issue

   `HttpEntity` created by `MultipartEntityBuilder` is wrapped into `BasicAsyncEntityProducer` as bytes, library sends the bytes as they are, and http post header missing boundary information.
-  Solution

   Get the `Content-Type` header including the boundery info then update it into request headers.
```java
//get the `Content-Type` header including the boundery info
//value is like:
//Content-Type: multipart/form-data; charset=ISO-8859-1; boundary=fLC0K1nKdSI-Q9vzFpU2WleMTXyWbOBp6
String contentType = reqEntity.getContentType();
final SimpleHttpRequest request = SimpleRequestBuilder
//...omit other methods
.setHeader(&quot;Content-Type&quot;, contentType)