Question

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

我希望将一个长字符串写入输出流。

使用HttpURLConnection，您可以像这样实现它：

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

是否有一种方法使用DefaultHttpClient类似于我上面的方法？如何使用OutputStream代替DefaultHttpClient来写HttpURLConnection？

例如

DefaultHttpClient client = new DefaultHttpClient();

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

Answer 1

我知道已经接受了另一个答案，只是为了记录，这就是如何用HttpClient写出内容而不在内存中进行中间缓冲。

    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。您必须创建一个HttpUriRequest对象，并为其提供一个HttpEntity，用于封装您要发送的内容。例如，如果您的输出足够小以适合内存，则可以执行以下操作：

// 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，您需要对其进行流式传输，则会变得更加困难，因为没有HttpEntity实现接受OutputStream。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，了解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 Client 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，执行程序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，因此上面示例中的外部准备和关闭代码很可能存在于bootstrap / init和finalization代码中，而不是直接与OutputStream实例化内联。

如何使用DefaultHttpClient写入OutputStream？

4 个答案: