Apache HttpClient 4 示例

2019-09-16 323 words One minute

Contents

1. 概述

本文展示了如何在各种示例和用例中使用 Apache HttpClient。

重点是HttpClient 4.3.x 及更高版本，因此某些示例可能不适用于旧版本的 API。

2. 示例

创建http客户端

CloseableHttpClient client = HttpClientBuilder.create().build();

发送基本 GET 请求

instance.execute(new HttpGet("http://www.google.com"));

获取 HTTP 响应的状态码

CloseableHttpResponse response = instance.execute(new HttpGet("http://www.google.com"));
assertThat(response.getStatusLine().getStatusCode(), equalTo(200));

获取响应的媒体类型

CloseableHttpResponse response = instance.execute(new HttpGet("http://www.google.com"));
String contentMimeType = ContentType.getOrDefault(response.getEntity()).getMimeType();
assertThat(contentMimeType, equalTo(ContentType.TEXT_HTML.getMimeType()));

获取响应的正文

CloseableHttpResponse response = instance.execute(new HttpGet("http://www.google.com"));
String bodyAsString = EntityUtils.toString(response.getEntity());
assertThat(bodyAsString, notNullValue());

配置请求的超时

@Test(expected = SocketTimeoutException.class)
public void givenLowTimeout_whenExecutingRequestWithTimeout_thenException() 
    throws ClientProtocolException, IOException {
    RequestConfig requestConfig = RequestConfig.custom()
      .setConnectionRequestTimeout(1000).setConnectTimeout(1000).setSocketTimeout(1000).build();
    HttpGet request = new HttpGet(SAMPLE_URL);
    request.setConfig(requestConfig);
    instance.execute(request);
}

在整个客户端上配置超时

RequestConfig requestConfig = RequestConfig.custom().
    setConnectionRequestTimeout(1000).setConnectTimeout(1000).setSocketTimeout(1000).build();
HttpClientBuilder builder = HttpClientBuilder.create().setDefaultRequestConfig(requestConfig);

发送 POST 请求

instance.execute(new HttpPost(SAMPLE_URL));

向请求添加参数

List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("key1", "value1"));
params.add(new BasicNameValuePair("key2", "value2"));
request.setEntity(new UrlEncodedFormEntity(params, Consts.UTF_8));

配置如何处理 HTTP 请求的重定向

CloseableHttpClient instance = HttpClientBuilder.create().disableRedirectHandling().build();
CloseableHttpResponse response = instance.execute(new HttpGet("http://t.co/I5YYd9tddw"));
assertThat(response.getStatusLine().getStatusCode(), equalTo(301));

配置请求的标头

HttpGet request = new HttpGet(SAMPLE_URL);
request.addHeader(HttpHeaders.ACCEPT, "application/xml");
response = instance.execute(request);

从响应中获取标头

CloseableHttpResponse response = instance.execute(new HttpGet(SAMPLE_URL));
Header[] headers = response.getHeaders(HttpHeaders.CONTENT_TYPE);
assertThat(headers, not(emptyArray()));

关闭/释放资源

response = instance.execute(new HttpGet(SAMPLE_URL));
try {
    HttpEntity entity = response.getEntity();
    if (entity != null) {
        InputStream instream = entity.getContent();
        instream.close();
    }
} finally {
    response.close();
}