1、先看一下示例程式碼

public class HttpClientTest {
    public static void main(String args[]) {
        //建立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 {
            //執行get請求
            HttpResponse httpResponse = closeableHttpClient.execute(httpGet);
            //獲取響應訊息實體
            HttpEntity entity = httpResponse.getEntity();
            //響應狀態
            System.out.println("status:" + httpResponse.getStatusLine());
            //判斷響應實體是否為空
            if (entity != null) {
                System.out.println("contentEncoding:" + entity.getContentEncoding());
                System.out.println("response content:" + EntityUtils.toString(entity));
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
 

                //關閉流並釋放資源
                closeableHttpClient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

2、HttpClientBuilder

HttpClientBuilder用於建立CloseableHttpClient例項。看了一下API文件，AbstractHttpClient、AutoRetryHttpClient、DefaultHttpClient等都被棄用了，使用HttpClientBuilder代替。

3、CloseableHttpClient

4、HttpGet

非執行緒安全；HttpGet有三個構造方法：HttpGet()、HttpGet(String uri)、HttpGet(URI uri)

5、HttpResponse

伺服器在接收和解釋請求之後返回一個HTTP響應資訊

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