Posting with HttpClient

1. Overview

In this tutorial – we’ll POST with the HttpClient 4 – using first authorization, then the fluent HttpClient API.

Finally, we’ll discuss how to Upload a File Using Httpclient.

2. Basic POST

First, let’s go over a simple example and send a POST request using HttpClient.

We’ll do a POST with two parameters – “username” and “password“:

@Test
public void whenSendPostRequestUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.example.com");

    List<NameValuePair> params = new ArrayList<NameValuePair>();
    params.add(new BasicNameValuePair("username", "John"));
    params.add(new BasicNameValuePair("password", "pass"));
    httpPost.setEntity(new UrlEncodedFormEntity(params));

    CloseableHttpResponse response = client.execute(httpPost);
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
    client.close();
}

Note how we used a List of NameValuePair to include parameters in the POST request.

3. POST With Authorization

Next, let’s see how to do a POST with Authentication credentials using the HttpClient.

In the following example – we send a POST request to a URL secured with Basic Authentication by adding an Authorization header:

@Test
public void whenSendPostRequestWithAuthorizationUsingHttpClient_thenCorrect()
  throws ClientProtocolException, IOException, AuthenticationException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.maixuanviet.com");

    httpPost.setEntity(new StringEntity("test post"));
    UsernamePasswordCredentials creds
      = new UsernamePasswordCredentials("John", "pass");
    httpPost.addHeader(new BasicScheme().authenticate(creds, httpPost, null));

    CloseableHttpResponse response = client.execute(httpPost);
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
    client.close();
}

4. POST With JSON

Now – let’s see how to send a POST request with a JSON body using the HttpClient.

In the following example – we’re sending some person information (id, name) as JSON:

@Test
public void whenPostJsonUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.maixuanviet.com");

    String json = "{"id":1,"name":"John"}";
    StringEntity entity = new StringEntity(json);
    httpPost.setEntity(entity);
    httpPost.setHeader("Accept", "application/json");
    httpPost.setHeader("Content-type", "application/json");

    CloseableHttpResponse response = client.execute(httpPost);
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
    client.close();
}

Note how we’re using the StringEntity to set the body of the request.

We’re also setting the ContentType header to application/json to give the server the necessary information about the representation of the content we’re sending.

5. POST With the HttpClient Fluent API

Next, let’s POST with the HttpClient Fluent API.

We’re going to send a request with two parameters “username” and “password“:

@Test
public void whenPostFormUsingHttpClientFluentAPI_thenCorrect() 
  throws ClientProtocolException, IOException {
    HttpResponse response = Request.Post("http://www.maixuanviet.com").bodyForm(
      Form.form().add("username", "John").add("password", "pass").build())
      .execute().returnResponse();

    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
}

6. POST Multipart Request

Now, let’s POST a Multipart Request.

We’ll post a File, username, and password using MultipartEntityBuilder:

@Test
public void whenSendMultipartRequestUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.maixuanviet.com");

    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.addTextBody("username", "John");
    builder.addTextBody("password", "pass");
    builder.addBinaryBody(
      "file", new File("test.txt"), ContentType.APPLICATION_OCTET_STREAM, "file.ext");

    HttpEntity multipart = builder.build();
    httpPost.setEntity(multipart);

    CloseableHttpResponse response = client.execute(httpPost);
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
    client.close();
}

7. Upload a File Using HttpClient

Next, let’s see how to upload a File using the HttpClient.

We’ll upload the “test.txt” file using MultipartEntityBuilder:

@Test
public void whenUploadFileUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.maixuanviet.com");

    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.addBinaryBody(
      "file", new File("test.txt"), ContentType.APPLICATION_OCTET_STREAM, "file.ext");
    HttpEntity multipart = builder.build();
    httpPost.setEntity(multipart);

    CloseableHttpResponse response = client.execute(httpPost);
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
    client.close();
}

8. Get File Upload Progress

Finally – let’s see how to get the progress of File upload using HttpClient.

In the following example, we’ll extend the HttpEntityWrapper to gain visibility into the upload process.

First – here’s the upload method:

@Test
public void whenGetUploadFileProgressUsingHttpClient_thenCorrect()
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.maixuanviet.com");

    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.addBinaryBody(
      "file", new File("test.txt"), ContentType.APPLICATION_OCTET_STREAM, "file.ext");
    HttpEntity multipart = builder.build();

    ProgressEntityWrapper.ProgressListener pListener = 
      percentage -> assertFalse(Float.compare(percentage, 100) > 0);
    httpPost.setEntity(new ProgressEntityWrapper(multipart, pListener));

    CloseableHttpResponse response = client.execute(httpPost);
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
    client.close();
}

We’ll also add the interface ProgressListener that enables us to observe the upload progress:

public static interface ProgressListener {
    void progress(float percentage);
}

And here’s our extended version of HttpEntityWrapper “ProgressEntityWrapper“:

public class ProgressEntityWrapper extends HttpEntityWrapper {
    private ProgressListener listener;

    public ProgressEntityWrapper(HttpEntity entity, ProgressListener listener) {
        super(entity);
        this.listener = listener;
    }

    @Override
    public void writeTo(OutputStream outstream) throws IOException {
        super.writeTo(new CountingOutputStream(outstream, listener, getContentLength()));
    }
}

And the extended version of FilterOutputStream “CountingOutputStream“:

public static class CountingOutputStream extends FilterOutputStream {
    private ProgressListener listener;
    private long transferred;
    private long totalBytes;

    public CountingOutputStream(
      OutputStream out, ProgressListener listener, long totalBytes) {
        super(out);
        this.listener = listener;
        transferred = 0;
        this.totalBytes = totalBytes;
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        out.write(b, off, len);
        transferred += len;
        listener.progress(getCurrentProgress());
    }

    @Override
    public void write(int b) throws IOException {
        out.write(b);
        transferred++;
        listener.progress(getCurrentProgress());
    }

    private float getCurrentProgress() {
        return ((float) transferred / totalBytes) * 100;
    }
}

Note that:

• When extending FilterOutputStream to “CountingOutputStream” – we are overriding the write() method to count the written (transferred) bytes
• When extending HttpEntityWrapper to “ProgressEntityWrapper” – we are overriding the writeTo() method to use our “CountingOutputStream”

9. Conclusion

In this tutorial, we illustrated the most common ways to send POST HTTP Requests with the Apache HttpClient 4.

We learned how to send a POST request with Authorization, how to post using HttpClient fluent API and how to upload a file and track its progress.

The implementation of all these examples and code snippets can be found in the github project.