【一】HttpClient4.3.1简单入门实例

1、先看一下示例代码

 public class HttpClientTest {
     public static void main(String args[]) {
         //创建HttpClientBuilder
         HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
         //HttpClient
         CloseableHttpClient closeableHttpClient = httpClientBuilder.build();

         HttpGet httpGet = new HttpGet("http://www.gxnu.edu.cn/default.html");
         System.out.println(httpGet.getRequestLine());
         try {
             //执行get请求
             HttpResponse httpResponse = closeableHttpClient.execute(httpGet);
             //获取响应消息实体
             HttpEntity entity = httpResponse.getEntity();
             //响应状态
             System.out.println("status:" + httpResponse.getStatusLine());
             //判断响应实体是否为空
             if (entity != null) {
                 System.out.println("contentEncoding:" + entity.getContentEncoding());
                 System.out.println("response content:" + EntityUtils.toString(entity));
             }
         } catch (IOException e) {
             e.printStackTrace();
         } finally {
             try {

             //关闭流并释放资源
             closeableHttpClient.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

以下内容来自 HttpClient4.3.1 API 文档： http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/overview-summary.html

2、HttpClientBuilder

HttpClientBuilder用于创建CloseableHttpClient实例。看了一下API文档，AbstractHttpClient、 AutoRetryHttpClient、 DefaultHttpClient等都被弃用了，使用HttpClientBuilder代替。

3、CloseableHttpClient

实现接口：Closeable, AutoCloseable, HttpClient；子类：AbstractHttpClient

4、HttpGet

非线程安全；HttpGet有三个构造方法：HttpGet()、HttpGet(String uri)、HttpGet(URI uri)

5、HttpResponse

服务器在接收和解释请求之后返回一个HTTP响应信息

     Response      = Status-Line
                     *(( general-header
                      | response-header
                      | entity-header ) CRLF)
                     CRLF
                     [ message-body ]