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一、前言

在現代的軟件開發中，經常需要與遠程服務器進行通信，例如獲取數據或發送數據。Apache HttpClient 是一個流行的 Java HTTP 客戶端庫，能夠簡化 HTTP 請求的發起和響應處理。本文將介紹如何使用自定義的 HttpClientUtils 類來利用 Apache HttpClient 發起 POST 請求，并且管理連接池以優化性能。

1.HttpClientUtils 類概覽

public class HttpClientUtils {// 靜態常量和變量聲明private static final int MAX_TOTAL_CONN = 600;private static final int MAX_CONN_PER_HOST = 300;private static final int SOCKET_TIMEOUT = 5000;private static final int CONNECTION_TIMEOUT = 200;private static final int CONNECTION_MANAGER_TIMEOUT = 100;private static CloseableHttpClient httpclient;private static PoolingHttpClientConnectionManager connMrg;private static String encoding = StandardCharsets.UTF_8.name();private static Logger log = LoggerFactory.getLogger(HttpClientUtils.class);private static final ScheduledExecutorService scheduledService = Executors.newScheduledThreadPool(2);// 靜態代碼塊，用于初始化 HttpClient 和連接管理器，并設置 JVM 退出時關閉 HttpClientstatic {init();destroyByJvmExit();}// 初始化連接管理器和 HttpClientprivate static void init() {connMrg = new PoolingHttpClientConnectionManager();connMrg.setMaxTotal(MAX_TOTAL_CONN);connMrg.setDefaultMaxPerRoute(MAX_CONN_PER_HOST);httpclient = HttpClients.custom().setConnectionManager(connMrg).setDefaultRequestConfig(HttpClientUtils.defaultRequestConfig()).build();// 定時任務，定期清理過期和空閑連接scheduledService.scheduleAtFixedRate(() -> {connMrg.closeExpiredConnections();connMrg.closeIdleConnections(CONNECTION_MANAGER_TIMEOUT, TimeUnit.MILLISECONDS);}, 0, CONNECTION_MANAGER_TIMEOUT, TimeUnit.MILLISECONDS);}// JVM 退出時關閉 HttpClientprivate static void destroyByJvmExit() {Runtime.getRuntime().addShutdownHook(new Thread(() -> {try {httpclient.close();} catch (IOException e) {log.error("Error closing HttpClient: {}", e.getMessage());}}));}// 創建 HttpClientContextprivate static HttpClientContext createContext() {return HttpClientContext.create();}// 創建默認的 RequestConfigprivate static RequestConfig defaultRequestConfig() {return RequestConfig.custom().setConnectTimeout(CONNECTION_TIMEOUT).setSocketTimeout(SOCKET_TIMEOUT).setConnectionRequestTimeout(CONNECTION_MANAGER_TIMEOUT).build();}// 發起帶參數的 POST 表單請求，返回字符串結果public static String postWithParamsForString(String url, List<NameValuePair> params) {HttpPost httpPost = new HttpPost();try {URI uri = new URIBuilder(url).build();httpPost.setURI(uri);httpPost.setEntity(new UrlEncodedFormEntity(params, StandardCharsets.UTF_8));return executeRequest(httpPost);} catch (URISyntaxException | IOException e) {log.error("Error executing POST request: {}", e.getMessage());} finally {httpPost.releaseConnection();}return null;}// 發起 GET 請求，返回字符串結果public static String get(String url, List<NameValuePair> params) {HttpGet httpGet = new HttpGet();try {URI uri = new URIBuilder(url).setParameters(params).build();httpGet.setURI(uri);return executeRequest(httpGet);} catch (URISyntaxException | IOException e) {log.error("HTTP GET request failed", e);} finally {httpGet.releaseConnection();}return null;}// 發起 Post 請求，返回字符串結果public static String post(String url, List<NameValuePair> params) {HttpPost httpPost = new HttpPost();try {httpPost.setURI(new URI(url));httpPost.setEntity(new UrlEncodedFormEntity(params, StandardCharsets.UTF_8));return executeRequest(httpPost);} catch (URISyntaxException | IOException e) {log.error("HTTP POST request failed", e);} finally {httpPost.releaseConnection();}return null;}// 執行 HTTP 請求并處理響應private static String executeRequest(HttpUriRequest request) throws IOException {try (CloseableHttpResponse response = httpclient.execute(request, createContext())) {int statusCode = response.getStatusLine().getStatusCode();if (statusCode == HttpStatus.SC_OK) {HttpEntity entity = response.getEntity();if (entity != null) {return EntityUtils.toString(entity, encoding);} else {log.warn("Empty response entity");}} else {log.error("HTTP request failed with status code: {}", statusCode);}} catch (IOException e) {log.error("HTTP request execution failed: {}", e.getMessage());throw e;}return null;}
}

2.解析 HttpClientUtils 類

1. 靜態常量和變量:

   • 定義了最大連接數、連接超時時間、Socket 超時時間等常量和變量。

2. 初始化和銷毀:

   • 在靜態代碼塊中初始化了 HttpClient 和連接管理器 PoolingHttpClientConnectionManager。
   • 使用 ScheduledExecutorService 定期清理過期和空閑連接。
   • 在 destroyByJvmExit 方法中，注冊了一個 JVM 退出鉤子，確保在 JVM 關閉時關閉 HttpClient。

3. HTTP 請求方法:

   • postWithParamsForString 方法用于執行帶參數的 POST 請求。
   • 使用 HttpPost 構建請求，設置 URL 和請求參數，最終調用 executeRequest 方法執行請求。

4. 執行請求和處理響應:

   • executeRequest 方法接收 HttpUriRequest，執行 HTTP 請求并處理響應。
   • 檢查響應的狀態碼，如果是 200（OK），則讀取響應實體并將其轉換為字符串返回。
   • 使用日志記錄錯誤和警告信息，確保代碼的健壯性和可靠性。

3.使用 HttpClientUtils 類

使用 HttpClientUtils 類可以簡化 HTTP 請求的編寫和管理，具體步驟如下：

public class Main {public static void main(String[] args) {List<NameValuePair> params = new ArrayList<>();params.add(new BasicNameValuePair("param1", "value1"));params.add(new BasicNameValuePair("param2", "value2"));String response = HttpClientUtils.postWithParamsForString("http://example.com/api", params);if (response != null) {System.out.println("Response: " + response);} else {System.err.println("Failed to execute POST request");}}
}

通過以上學習，你現在應該了解如何使用 HttpClientUtils 類來管理 HTTP 客戶端和發起請求。這種方式可以幫助你在 Java 應用中更高效地處理 HTTP 通信，同時通過連接池和定期清理機制提升性能和穩定性。