步驟:

1. 建立HttpClient物件。

2. 建立請求方法的例項，並指定請求URL。如果需要傳送GET請求，建立HttpGet物件；如果需要傳送POST請求，建立HttpPost物件。

3. 如果需要傳送請求引數，可呼叫HttpGet、HttpPost共同的setParams(HetpParams params)方法來新增請求引數；對於HttpPost物件而言，也可呼叫setEntity(HttpEntity entity)方法來設定請求引數。

4. 呼叫HttpClient物件的execute(HttpUriRequest request)傳送請求，該方法返回一個HttpResponse。

5. 呼叫HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取伺服器的響應頭；呼叫HttpResponse的getEntity()方法可獲取HttpEntity物件，該物件包裝了伺服器的響應內容。程式可通過該物件獲取伺服器的響應內容。

6. 釋放連線。無論執行方法是否成功，都必須釋放連線

程式碼:

/**
     * httpClient post請求
     * @param url 請求url
     * @param header 頭部資訊
     * @param param 請求引數 form提交適用
     * @param entity 請求實體 json/xml提交適用
     * @return 可能為空 需要處理
     * @throws Exception
     *
     */
    public static String post(String  url, Map<String, String> header, Map<String, String> param, HttpEntity entity) throws Exception {
        String result = "";
        CloseableHttpClient httpClient = null;
        try {
            httpClient = getHttpClient();
 

            HttpPost httpPost = new HttpPost(url);
            // 設定頭資訊
            if (MapUtils.isNotEmpty(header)) {
                for (Map.Entry<String, String> entry : header.entrySet()) {
                    httpPost.addHeader(entry.getKey(), entry.getValue());
                }
            }
            // 設定請求引數
            if (MapUtils.isNotEmpty(param)) {
                List<NameValuePair> formparams = new ArrayList<NameValuePair>();
                for (Map.Entry<String, String> entry : param.entrySet()) {
                    //給引數賦值
                    formparams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
                }
                UrlEncodedFormEntity urlEncodedFormEntity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);
                httpPost.setEntity(urlEncodedFormEntity);
            }
            // 設定實體 優先順序高
            if (entity != null) {
                httpPost.setEntity(entity);
            }
            HttpResponse httpResponse = httpClient.execute(httpPost);
            int statusCode = httpResponse.getStatusLine().getStatusCode();
            if (statusCode == HttpStatus.SC_OK) {
                HttpEntity resEntity = httpResponse.getEntity();
                result = EntityUtils.toString(resEntity);
            } else {
                readHttpResponse
 
(httpResponse);
            }
        } catch (Exception e) {throw e;
        } finally {
            if (httpClient != null) {
                httpClient.close();
            }
        }
        return result;
    }

public static String readHttpResponse(HttpResponse httpResponse)
            throws ParseException, IOException {
        StringBuilder builder = new StringBuilder();
        // 獲取響應訊息實體
        HttpEntity entity = httpResponse.getEntity();
        // 響應狀態
        builder.append("status:" + httpResponse.getStatusLine());
        builder.append("headers:");
        HeaderIterator iterator = httpResponse.headerIterator();
        while (iterator.hasNext()) {
            builder.append("\t" + iterator.next());
        }
        // 判斷響應實體是否為空
        if (entity != null) {
            String responseString = EntityUtils.toString(entity);
            builder.append("response length:" + responseString.length());
            builder.append("response content:" + responseString.replace("\r\n", ""));
        }
        return builder.toString();
    }

 public static CloseableHttpClient getHttpClient() throws Exception {
        CloseableHttpClient httpClient = HttpClients.custom()
                .setSSLSocketFactory(sslsf)
                .setConnectionManager(cm)
                .setConnectionManagerShared(true)
                .build();
        return httpClient;
    }