在實際項目中，經常會遇到調用外部（第三方）的接口，如果調用量較大的話，可能需要考慮連接池、失敗重試、SSL證書等問題，以提升性能和穩定性。

以下代碼是封裝的小組件，供大家參考。

• maven依賴

<dependency><groupId>org.apache.httpcomponents</groupId><artifactId>httpclient</artifactId><version>4.5.6</version></dependency>

• HttpUtil.java代碼：

import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.HttpStatus; import org.apache.http.NameValuePair; import org.apache.http.client.HttpRequestRetryHandler; import org.apache.http.client.config.RequestConfig; import org.apache.http.client.entity.UrlEncodedFormEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpPost; import org.apache.http.config.Registry; import org.apache.http.config.RegistryBuilder; import org.apache.http.conn.HttpClientConnectionManager; import org.apache.http.conn.socket.ConnectionSocketFactory; import org.apache.http.conn.socket.PlainConnectionSocketFactory; import org.apache.http.conn.ssl.DefaultHostnameVerifier; import org.apache.http.conn.ssl.SSLConnectionSocketFactory; import org.apache.http.entity.StringEntity; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.impl.client.HttpClients; import org.apache.http.impl.conn.PoolingHttpClientConnectionManager; import org.apache.http.message.BasicNameValuePair; import org.apache.http.util.EntityUtils; import org.springframework.util.CollectionUtils;import javax.exceptions.ServiceException; import javax.net.ssl.KeyManagerFactory; import javax.net.ssl.SSLContext; import java.io.IOException; import java.io.InputStream; import java.security.KeyStore; import java.security.SecureRandom; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map;/*** http/https工具類。* 支持線程池管理、failRetry特性。*/ public class HttpUtil {private static final String DEFAULT_CHARSET = "UTF-8";private static CloseableHttpClient httpClient;public static String get(final String url) throws Exception {return getExecute(url, null, getHttpClient(null), null);}public static String get(final String url, final Map<String, Object> paramMap) throws Exception {return getExecute(url, paramMap, getHttpClient(null), null);}public static String get(final String url, final Map<String, Object> paramMap, final Map<String, String> headers) throws Exception {return getExecute(url, paramMap, getHttpClient(null), headers);}/*** POST請求，支持失敗重試。*/public static String post(final String url, final Map<String, Object> paramMap) throws Exception {return postExecute(url, paramMap, new HashMap<>(), getHttpClient(null));}/*** POST請求，支持失敗重試。*/public static String postRetry(final String url, final Map<String, Object> paramMap, final Map<String, String> headers) throws Exception {return postExecute(url, paramMap, headers, getHttpClient(null));}/*** POST請求，支持失敗重試。*/public static String postRetry(final String url, final String paramStr,final CertInfo certInfo, final Map<String, String> headers) throws Exception {return postExecute(url, paramStr, headers, getHttpClient(certInfo));}/*** POST請求，支持失敗重試。*/public static String postRetry(final String url, final Map<String, Object> paramMap,final CertInfo certInfo, final Map<String, String> headers) throws Exception {return postExecute(url, paramMap, headers, getHttpClient(certInfo));}private static synchronized CloseableHttpClient getHttpClient(final CertInfo certInfo) {if (null == certInfo && null != httpClient) {return httpClient;} else {//https請求暫不走httpClient緩存，因為每次請求可能使用不同的證書。RequestConfig config = RequestConfig.custom().setSocketTimeout(Constants.HTTP_READ_TIMEOUT_MS).setConnectTimeout(Constants.HTTP_CONNECTION_TIMEOUT_MS).build();HttpClientConnectionManager connManager = getPoolConnManager(certInfo);HttpRequestRetryHandler retryHandler = RetryHandler.getHandler(Constants.DEFAULT_HTTP_RETRY_MAX_TIMES, Constants.DEFAULT_HTTP_RETRY_INTERVAL_MILLIS);httpClient = HttpClients.custom().setConnectionManager(connManager).setDefaultRequestConfig(config).setRetryHandler(retryHandler).build();//jvm關閉時，釋放連接Runtime.getRuntime().addShutdownHook(new Thread(() -> {try {httpClient.close();} catch (IOException e) {//catched}}));return httpClient;}}/*** 獲取 連接管理器實例 。* 支持http/https和連接池。*/private static HttpClientConnectionManager getPoolConnManager(final CertInfo certInfo) {Registry<ConnectionSocketFactory> registry;if (null != certInfo) {certInfo.validate();try {// 證書char[] password = certInfo.getPassword().toCharArray();InputStream certStream = certInfo.getCertStream();KeyStore ks = KeyStore.getInstance("PKCS12");ks.load(certStream, password);// 實例化密鑰庫 & 初始化密鑰工廠KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());kmf.init(ks, password);// 創建 SSLContextSSLContext sslContext = SSLContext.getInstance("TLS");sslContext.init(kmf.getKeyManagers(), null, new SecureRandom());SSLConnectionSocketFactory sslConnectionSocketFactory = new SSLConnectionSocketFactory(sslContext,new String[]{"TLSv1"},null,new DefaultHostnameVerifier());registry = RegistryBuilder.<ConnectionSocketFactory>create().register("https", sslConnectionSocketFactory).register("http", PlainConnectionSocketFactory.getSocketFactory()).build();} catch (Exception e) {throw new ServiceException(ErrorCodeEnums.InternalServerError, "創建 SSLContext 失敗，證書初始化失敗");}} else {registry = RegistryBuilder.<ConnectionSocketFactory>create().register("http", PlainConnectionSocketFactory.getSocketFactory()).register("https", SSLConnectionSocketFactory.getSocketFactory()).build();}PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);//http連接池: 最大連接數，默認20connectionManager.setMaxTotal(Constants.HTTP_POOL_MAX_TOTAL);//http連接池: 每個路由的并發連接，默認2connectionManager.setDefaultMaxPerRoute(Constants.HTTP_POOL_MAX_PER_ROUTE);return connectionManager;}/*** 執行POST請求。*/private static String postExecute(String url, String data, Map<String, String> headers,CloseableHttpClient closeableHttpClient) throws IOException {HttpPost httpPost = new HttpPost(url);if (!CollectionUtils.isEmpty(headers)) {headers.forEach(httpPost::addHeader);}StringEntity postEntity = new StringEntity(data, DEFAULT_CHARSET);httpPost.setEntity(postEntity);HttpResponse httpResponse = closeableHttpClient.execute(httpPost);int httpStatus = httpResponse.getStatusLine().getStatusCode();if (HttpStatus.SC_OK != httpStatus) {System.err.println(url + "接口調用失敗，返回狀態碼:" + httpStatus);}HttpEntity httpEntity = httpResponse.getEntity();return EntityUtils.toString(httpEntity, DEFAULT_CHARSET);}private static String postExecute(String url, Map<String, Object> params, Map<String, String> headers,CloseableHttpClient closeableHttpClient) throws IOException {HttpPost httpPost = new HttpPost(url);if (headers != null && !headers.isEmpty()) {headers.forEach(httpPost::addHeader);}List<NameValuePair> pairList = new ArrayList<>(params.size());for (Map.Entry<String, Object> entry : params.entrySet()) {NameValuePair pair = new BasicNameValuePair(entry.getKey(), entry.getValue().toString());pairList.add(pair);}httpPost.setEntity(new UrlEncodedFormEntity(pairList, DEFAULT_CHARSET));HttpResponse httpResponse = closeableHttpClient.execute(httpPost);int httpStatus = httpResponse.getStatusLine().getStatusCode();if (HttpStatus.SC_OK != httpStatus) {System.err.println(url + "接口調用失敗，返回狀態碼:" + httpStatus);}HttpEntity httpEntity = httpResponse.getEntity();return EntityUtils.toString(httpEntity, DEFAULT_CHARSET);}private static String getExecute(String url, Map<String, Object> params, CloseableHttpClient closeableHttpClient, Map<String, String> headers) throws IOException {CloseableHttpResponse response;if (!CollectionUtils.isEmpty(params)) {StringBuilder realUrl = new StringBuilder().append(url).append("?");for (String key : params.keySet()) {realUrl.append(key).append("=").append(params.get(key)).append("&");}url = realUrl.substring(0, realUrl.length() - 1);}HttpGet httpGet = new HttpGet(url);if (!CollectionUtils.isEmpty(headers)) {headers.forEach(httpGet::addHeader);}response = closeableHttpClient.execute(httpGet);int httpStatus = response.getStatusLine().getStatusCode();if (HttpStatus.SC_OK != httpStatus) {System.err.println(url + "接口調用失敗，返回狀態碼:" + httpStatus);}return EntityUtils.toString(response.getEntity(), DEFAULT_CHARSET);} }

• Constants 常量類:

public class Constants {// --------------------- http配置相關 start ------------------/*** HTTP連接超時時間。*/public static final int HTTP_CONNECTION_TIMEOUT_MS = 3000;/*** http read timeout*/public static final int HTTP_READ_TIMEOUT_MS = 25000;/*** http連接池: 最大連接數，默認20**/public static final int HTTP_POOL_MAX_TOTAL = 32;/*** http連接池: 每個路由的并發連接，默認2**/public static final int HTTP_POOL_MAX_PER_ROUTE = 16;/*** http失敗重試: 默認最大重試次數。*/public static final int DEFAULT_HTTP_RETRY_MAX_TIMES = 2;/*** http失敗重試: 默認每次的間隔時間。默認為1秒。*/public static final Integer DEFAULT_HTTP_RETRY_INTERVAL_MILLIS = 1000;// --------------------- http配置相關 end ------------------ }

• ErrorCodeEnums.java類：

public enum ErrorCodeEnums {InternalServerError(500, "服務器內部錯誤"), }

• SSL證書類CertInfo.java：

import org.springframework.util.Assert;import java.io.InputStream; /*** 發起HTTPS/SSL使用的證書。** */ public class CertInfo {//證書密碼（口令）private String password;//證書文件private InputStream certStream;public String getPassword() {return password;}public CertInfo setPassword(String password) {this.password = password;return this;}public InputStream getCertStream() {return certStream;}public CertInfo setCertStream(InputStream certStream) {this.certStream = certStream;return this;}public void validate() {Assert.hasLength(password, "password不能為空");Assert.notNull(certStream, "certStream不能為空");} }

• HTTP重試策略類：

import org.apache.http.HttpEntityEnclosingRequest; import org.apache.http.HttpRequest; import org.apache.http.NoHttpResponseException; import org.apache.http.client.HttpRequestRetryHandler; import org.apache.http.client.protocol.HttpClientContext; import org.apache.http.conn.ConnectTimeoutException; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger;import javax.net.ssl.SSLException; import javax.net.ssl.SSLHandshakeException; import java.io.IOException; import java.io.InterruptedIOException; import java.net.UnknownHostException;/*** HTTP重試策略。** @author machunlin* @date 2018/4/26*/ public class RetryHandler {private static final Logger LOGGER = LogManager.getLogger(RetryHandler.class);/*** 自定義HTTP重試策略。** @param maxRetryTimes 最大重試次數* @param intervalMillis 重試間隔時間，毫秒* @return*/public static HttpRequestRetryHandler getHandler(final Integer maxRetryTimes, final Integer intervalMillis) {if (maxRetryTimes == null || maxRetryTimes <= 0) {throw new IllegalArgumentException("maxRetryTimes參數不合法：" + maxRetryTimes);}return (exception, executionCount, context) -> {if (executionCount > maxRetryTimes) {LOGGER.error(" 已超過最大重試次數。 當前為第{}次重試，最大重試次數為{}", executionCount, maxRetryTimes, exception);return false;}try {long interval = (null != intervalMillis) ? intervalMillis : Constants.DEFAULT_HTTP_RETRY_INTERVAL_MILLIS;long nextInterval = interval * executionCount;Thread.sleep(nextInterval);} catch (InterruptedException e) {//聲明線程狀態為"可中斷的"。Thread.currentThread().interrupt();}if (exception instanceof UnknownHostException) {LOGGER.error("目標服務器不可達, Unknown host", exception);return false;}if (exception instanceof ConnectTimeoutException) {LOGGER.error("連接被拒絕,ConnectTimeout ", exception);return true;}if (exception instanceof InterruptedIOException) {LOGGER.error("連接超時, Timeout", exception);return true;}if (exception instanceof IOException) {LOGGER.error("網絡異常, IOException", exception);return true;}if (exception instanceof SSLHandshakeException) {LOGGER.error("SSL握手異常,SSLHandshakeException ", exception);return false;}if (exception instanceof SSLException) {LOGGER.error("SSLException exception", exception);return false;}if (exception instanceof NoHttpResponseException) {// 如果服務器丟掉了連接，那么就重試return true;}if (exception instanceof Exception) {return true;}HttpClientContext clientContext = HttpClientContext.adapt(context);HttpRequest request = clientContext.getRequest();if (!(request instanceof HttpEntityEnclosingRequest)) {// 如果請求是冪等的，就再次嘗試return true;}LOGGER.error("HttpRequestRetryHandler, return false");return false;};} }

總結

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