HttpClient 4.x POST请求（基础篇）

教程分享 > Java教程 (2846) 2024-04-19 10:12:55

1.概述

在本教程中 - 我们将使用HttpClient 4进行POST - 首先使用授权，然后使用流畅的HttpClient API。最后 - 我们将讨论如何使用HttpClient上传文件。

2.基本POST

首先，我们来看一个简单的例子，并使用HttpClient发送POST请求。

在以下示例中 - 我们将使用两个参数 - “ 用户名 ”和“ 密码 ” 进行POST ：

@Test
public void whenPostRequestUsingHttpClient_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();
}

注意我们是如何使用的列表中的NameValuePair包括POST请求的参数。

3.带授权的POST

接下来 - 让我们看看如何使用HttpClient执行带有身份验证凭证的POST 。

在下面的例子中 - 我们发送一个发布请求到一个使用基本身份验证保护的URL：

@Test
public void whenPostRequestWithAuthorizationUsingHttpClient_thenCorrect()
  throws ClientProtocolException, IOException, AuthenticationException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.example.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.使用JSON进行POST

现在让我们看看如何使用HttpClient发送带有JSON正文的POST请求。

在以下示例中 - 我们将一些人员信息（id，name）作为JSON发送：

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

请注意我们如何使用StringEntity来设置请求的主体。

我们还将ContentType标头设置为application / json，以向服务器提供有关我们发送的内容表示的必要信息。

**5.使用HttpClient Fluent API进行 POST**

接下来 - 让我们使用HttpClient Fluent API进行 POST ; 我们将发送带有两个参数“ 用户名 ”和“ 密码 ” 的请求：

@Test
public void whenPostFormUsingHttpClientFluentAPI_thenCorrect() 
  throws ClientProtocolException, IOException {
    HttpResponse response = 
      Request.Post("http://www.example.com").bodyForm(
        Form.form().add("username", "John").add("password", "pass").build())
        .execute().returnResponse();
 
    assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
}

6. POST多部分请求

现在 - 让我们发布一个Multipart Request - 在下面的例子中，我们将使用MultipartEntityBuilder发布文件，用户名和密码：

@Test
public void whenSendMultipartRequestUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.example.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. 使用HttpClient上传文件**

接下来 - 让我们看看如何使用HttpClient上传文件 - 我们将使用MultipartEntityBuilder上传“ test.txt ”文件：

@Test
public void whenUploadFileUsingHttpClient_thenCorrect() 
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.example.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.获取文件上传进度

最后 - 让我们看看如何使用HttpClient获得文件上传的进度。在下面的例子中 - 我们将扩展HttpEntityWrapper以获取上传过程的可见性：

首先 - 这是上传方法：

@Test
public void whenGetUploadFileProgressUsingHttpClient_thenCorrect()
  throws ClientProtocolException, IOException {
    CloseableHttpClient client = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://www.example.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 = 
     new ProgressEntityWrapper.ProgressListener() {
        @Override
        public void progress(float 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();
}

这里是接口ProgressListener，它使我们能够观察上传进度：

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

在这里我们扩展版本的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()));
    }
}

和FilterOutputStream的扩展版本“ 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;
    }
}

注意：

当将FilterOutputStream扩展为“ CountingOutputStream ”时 -我们重写write（）方法来计算写入（传输）的字节
当将HttpEntityWrapper扩展为“ ProgressEntityWrapper”时 -我们重写writeTo（）方法以使用我们的“ CountingOutputStream ”