如何使用 DefaultHttpClient 写入 OutputStream？

Question

如何使用org.apache.http.impl.client.DefaultHttpClient 获得OutputStream？

我希望将长字符串写入输出流。

使用HttpURLConnection 你可以这样实现它：

HttpURLConnection connection = (HttpURLConnection)url.openConnection();
OutputStream out = connection.getOutputStream();
Writer wout = new OutputStreamWriter(out);
writeXml(wout);

有没有类似于我上面的使用DefaultHttpClient 的方法？我如何使用DefaultHttpClient 而不是HttpURLConnection 给OutputStream 写信？

例如

DefaultHttpClient client = new DefaultHttpClient();

OutputStream outstream = (get OutputStream somehow)
Writer wout = new OutputStreamWriter(out);

Answer 1

我知道另一个答案已经被接受，只是为了记录，这是一个可以使用 HttpClient 写出内容而无需在内存中进行中间缓冲的方法。

    AbstractHttpEntity entity = new AbstractHttpEntity() {

        public boolean isRepeatable() {
            return false;
        }

        public long getContentLength() {
            return -1;
        }

        public boolean isStreaming() {
            return false;
        }

        public InputStream getContent() throws IOException {
            // Should be implemented as well but is irrelevant for this case
            throw new UnsupportedOperationException();
        }

        public void writeTo(final OutputStream outstream) throws IOException {
            Writer writer = new OutputStreamWriter(outstream, "UTF-8");
            writeXml(writer);
            writer.flush();
        }

    };
    HttpPost request = new HttpPost(uri);
    request.setEntity(entity);

Answer 2

您无法直接从 BasicHttpClient 获取 OutputStream。你必须创建一个HttpUriRequest 对象并给它一个HttpEntity 来封装你想要发送的内容。例如，如果您的输出足够小以适合内存，您可以执行以下操作：

// Produce the output
ByteArrayOutputStream out = new ByteArrayOutputStream();
Writer writer = new OutputStreamWriter(out, "UTF-8");
writeXml(writer);

// Create the request
HttpPost request = new HttpPost(uri);
request.setEntity(new ByteArrayEntity(out.toByteArray()));

// Send the request
DefaultHttpClient client = new DefaultHttpClient();
HttpResponse response = client.execute(request);

如果数据足够大以至于您需要对其进行流式传输，则变得更加困难，因为没有接受 OutputStream 的HttpEntity 实现。您需要写入临时文件并使用 FileEntity 或可能设置管道并使用 InputStreamEntity

编辑请参阅 oleg 的答案以获取演示如何流式传输内容的示例代码 - 毕竟您不需要临时文件或管道。

Answer 3

这在 android 上运行良好。它也应该适用于大文件，因为不需要缓冲。

PipedOutputStream out = new PipedOutputStream();
PipedInputStream in = new PipedInputStream();
out.connect(in);
new Thread() {
    @Override
    public void run() {
        //create your http request
        InputStreamEntity entity = new InputStreamEntity(in, -1);
        request.setEntity(entity);
        client.execute(request,...);
        //When this line is reached your data is actually written
    }
}.start();
//do whatever you like with your outputstream.
out.write("Hallo".getBytes());
out.flush();
//close your streams

Answer 4

我写了一个 Apache 的 HTTP 客户端 API [PipedApacheClientOutputStream] 的反转，它使用 Apache Commons HTTP 客户端 4.3.4 为 HTTP POST 提供了一个 OutputStream 接口。

调用代码如下所示：

// Calling-code manages thread-pool
ExecutorService es = Executors.newCachedThreadPool(
  new ThreadFactoryBuilder()
  .setNameFormat("apache-client-executor-thread-%d")
  .build());


// Build configuration
PipedApacheClientOutputStreamConfig config = new      
  PipedApacheClientOutputStreamConfig();
config.setUrl("http://localhost:3000");
config.setPipeBufferSizeBytes(1024);
config.setThreadPool(es);
config.setHttpClient(HttpClientBuilder.create().build());

// Instantiate OutputStream
PipedApacheClientOutputStream os = new     
PipedApacheClientOutputStream(config);

// Write to OutputStream
os.write(...);

try {
  os.close();
} catch (IOException e) {
  logger.error(e.getLocalizedMessage(), e);
}

// Do stuff with HTTP response
...

// Close the HTTP response
os.getResponse().close();

// Finally, shut down thread pool
// This must occur after retrieving response (after is) if interested   
// in POST result
es.shutdown();

注意 - 实际上，相同的客户端、执行器服务和配置可能会在应用程序的整个生命周期中重复使用，因此上述示例中的外部准备和关闭代码可能会存在于 bootstrap/init 和终结代码中，而不是直接与 OutputStream 实例化内联。