简述
本文学习如何简单的使用POST，如何上传文件等等场景
基础POST
首先，让我们来看一个简单的例子，并使用HttpClient发送POST请求。
我们将使用两个参数 - “username”和“password” 进行POST ：
@Test
public void test()
throws ClientProtocolException, IOException {
CloseableHttpClient client = HttpClients.createDefault();
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", "John"));
params.add(new BasicNameValuePair("password", "pass"));
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpPost httpPost = new HttpPost("http://localhost:8080");
CloseableHttpResponse response = client.execute(httpPost);
assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
client.close();
}
请注意我们如何使用List<NameValuePair>在POST请求中包含参数。
使用授权进行POST
接下来，让我们看看如何使用HttpClient对身份验证凭据进行POST 。
在以下示例中 - 我们通过添加Authorization在Header向使用基本身份验证保护的URL发送POST请求：
@Test
public void test()
throws ClientProtocolException, IOException, AuthenticationException {
CloseableHttpClient client = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://localhost:8080");
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();
}
使用JSON POST
现在 - 让我们看看如何使用HttpClient向JSON主体发送POST请求。
在以下示例中 - 我们将一些Person（id，name）作为JSON发送：
@Test
public void test()
throws ClientProtocolException, IOException {
CloseableHttpClient client = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://localhost:8080");
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();
}
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 ，以便为服务器提供有关我们发送的内容表示的必要信息。
使用HttpClient Form进行 POST
接下来，让我们使用HttpClient Fluent API进行POST 。
我们将发送一个带有两个参数“ username ”和“ password ” 的请求：
@Test
public void test()
throws ClientProtocolException, IOException {
HttpResponse response = Request.Post("http://localhost:8080").bodyForm(
Form.form().add("username", "John").add("password", "pass").build())
.execute().returnResponse();
assertThat(response.getStatusLine().getStatusCode(), equalTo(200));
}
POST多参数请求
现在，让我们发一个多参数请求。
我们将使用MultipartEntityBuilder发布文件，useranme和password：
@Test
public void whenSendMultipartRequestUsingHttpClient_thenCorrect()
throws ClientProtocolException, IOException {
CloseableHttpClient client = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://localhost:8080");
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();
}
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 test() throws ClientProtocolException, IOException {
CloseableHttpClient client = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://localhost:8080");
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();
}
获取文件上传 进度
最后 - 让我们看看如何使用HttpClient获取文件上传的进度。
在下面的示例中，我们将扩展HttpEntityWrapper以获得对上载过程的可见性。
首先 - 这是上传方法：
@Test
public void test()
throws ClientProtocolException, IOException {
CloseableHttpClient client = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://localhost:8080");
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();
}
我们还将添加接口ProgressListener，使我们能够观察上传进度：
public static interface ProgressListener {
void progress(float percentage);
}
这是我们的扩展版HttpEntityWrapper的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()));
}
}
而FilterOutputStream的扩展版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：
- 将FilterOutputStream扩展为
CountingOutputStream时 -我们重写write（）方法来计算写入（传输）的字节数 - 将HttpEntityWrapper扩展为
ProgressEntityWrapper时 -我们重写writeTo（）方法以使用我们的CountingOutputStream
小结
HttpClient的基础知识到本文就已经介绍结束，希望对你有所收获。
