httpclient org.apache.http.NoHttpResponseException: host:端口 failed to respond 错误原因和解决方法

• 原因：httpclient 之前与服务端建立的链接已经失效（例如：tomcat 默认的keep-alive timeout ：20s），再次从连接池拿该失效链接进行请求时，就会保存。
• 解决方法：官方链接：http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html#d5e659
• 上面官方链接的2.6 解决方法的代码如果报错，可能是自己的httpclient版本 不适用。自己用的是httpclient 4.0.1，使用以下代码绿色代码：

  import com.google.api.client.http.ByteArrayContent;
  import com.google.api.client.http.GenericUrl;
  import com.google.api.client.http.HttpBackOffUnsuccessfulResponseHandler;
  import com.google.api.client.http.HttpContent;
  import com.google.api.client.http.HttpHeaders;
  import com.google.api.client.http.HttpRequest;
  import com.google.api.client.http.HttpRequestFactory;
  import com.google.api.client.http.HttpResponse;
  import com.google.api.client.http.HttpStatusCodes;
  import com.google.api.client.http.HttpTransport;
  import com.google.api.client.http.apache.ApacheHttpTransport;
  import com.google.api.client.util.BackOff;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.ProxySelector;
  import java.util.Map;
  import java.util.Timer;
  import java.util.TimerTask;
  import java.util.concurrent.TimeUnit;
  import javax.annotation.PreDestroy;
  import lombok.Data;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.http.HeaderElement;
  import org.apache.http.HeaderElementIterator;
  import org.apache.http.HttpHost;
  import org.apache.http.conn.ClientConnectionManager;
  import org.apache.http.conn.ConnectionKeepAliveStrategy;
  import org.apache.http.conn.params.ConnManagerParams;
  import org.apache.http.conn.params.ConnPerRouteBean;
  import org.apache.http.conn.scheme.PlainSocketFactory;
  import org.apache.http.conn.scheme.Scheme;
  import org.apache.http.conn.scheme.SchemeRegistry;
  import org.apache.http.conn.ssl.SSLSocketFactory;
  import org.apache.http.impl.client.DefaultHttpClient;
  import org.apache.http.impl.client.DefaultHttpRequestRetryHandler;
  import org.apache.http.impl.conn.ProxySelectorRoutePlanner;
  import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
  import org.apache.http.message.BasicHeaderElementIterator;
  import org.apache.http.params.BasicHttpParams;
  import org.apache.http.params.HttpConnectionParams;
  import org.apache.http.params.HttpParams;
  import org.apache.http.protocol.HTTP;
  import org.apache.http.protocol.HttpContext;
   
  /**
   * @author Li Sheng
   */
  @Slf4j
  public class HttpClientUtils {
   
    private static HttpRequestFactory requestFactory;
    private static HttpTransport httpTransport;
    private static final String CONTENT_TYPE_JSON = "application/json";
   
    private static final int CACHE_SIZE = 4096;
   
    static {
   
      HttpParams params = new BasicHttpParams();
      HttpConnectionParams.setStaleCheckingEnabled(params, false);
      HttpConnectionParams.setSocketBufferSize(params, 245760); // 8k(8192) * 30
      ConnManagerParams.setMaxTotalConnections(params, 400);
      ConnManagerParams.setMaxConnectionsPerRoute(params, new ConnPerRouteBean(200));
   
      SchemeRegistry registry = new SchemeRegistry();
      registry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));
      registry.register(new Scheme("https", SSLSocketFactory.getSocketFactory(), 443));
      ClientConnectionManager connectionManager = new ThreadSafeClientConnManager(params, registry);
   
      DefaultHttpClient defaultHttpClient = new DefaultHttpClient(connectionManager, params);
      defaultHttpClient.setHttpRequestRetryHandler(new DefaultHttpRequestRetryHandler(0, false));
      defaultHttpClient
          .setRoutePlanner(new ProxySelectorRoutePlanner(registry, ProxySelector.getDefault()));
   
      ConnectionKeepAliveStrategy connectionKeepAliveStrategy = new ConnectionKeepAliveStrategy() {
        @Override
        public long getKeepAliveDuration(org.apache.http.HttpResponse httpResponse,
            HttpContext httpContext) {
          return 20 * 1000; // 20 seconds,because tomcat default keep-alive timeout is 20s
        }
      };
      defaultHttpClient.setKeepAliveStrategy(connectionKeepAliveStrategy);
   
      httpTransport = new ApacheHttpTransport(defaultHttpClient);
   
      requestFactory = httpTransport.createRequestFactory();
   
    }
   
    @Data
    public static class PostParam {
   
      private Integer connectTimeoutMills;  // 可选,默认 20s
      private Integer readTimeoutMills;  // 可选，默认 20s
      private Map<String, String> headers; // 可选
      private String url; //必填
      private String postJson; //必填
      private Boolean readResponseData; //必填：是否需要读取数据。如果不需要返回结果,设置 false
      private BackOff backOff; //可选,重试机制策略
      private String authorization; //可选
   
      public PostParam(String url, String postJson, boolean readResponseData) {
        this.url = url;
        this.postJson = postJson;
        this.readResponseData = readResponseData;
      }
    }
   
    public static String postWithJson(PostParam postParam) {
      GenericUrl genericUrl = new GenericUrl(postParam.getUrl());
      HttpContent httpContent = ByteArrayContent.fromString(null, postParam.getPostJson());
      HttpResponse httpResponse = null;
      try {
        HttpRequest httpRequest = requestFactory.buildPostRequest(genericUrl, httpContent);
        if (postParam.getConnectTimeoutMills() != null) {
          httpRequest.setConnectTimeout(postParam.getConnectTimeoutMills());
        }
        if (postParam.getReadTimeoutMills() != null) {
          httpRequest.setReadTimeout(postParam.getReadTimeoutMills());
        }
        if (postParam.getBackOff() != null) {
          httpRequest.setUnsuccessfulResponseHandler(
              new HttpBackOffUnsuccessfulResponseHandler(postParam.getBackOff()));
        }
   
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.setContentType(CONTENT_TYPE_JSON);
        Map<String, String> headers = postParam.getHeaders();
        if (headers != null && headers.size() > 0) {
          headers.forEach(httpHeaders::set);
        }
        if (postParam.getAuthorization() != null && !postParam.equals("")) {
          httpHeaders.setAuthorization(postParam.getAuthorization());
        }
   
        httpRequest.setHeaders(httpHeaders);
        httpResponse = httpRequest.execute();
        if (httpResponse.getStatusCode() != HttpStatusCodes.STATUS_CODE_OK) {
          log.error("http status not 200. param:{},status:{},msg:{}", postParam,
              httpResponse.getStatusCode(), httpResponse.getStatusMessage());
          return null;
        }
        Boolean readResponseData = postParam.getReadResponseData();
        if (readResponseData != null && readResponseData) {
          InputStream inputStream = httpResponse.getContent();
          if (inputStream != null) {
            StringBuffer out = new StringBuffer();
            byte[] b = new byte[CACHE_SIZE];
            for (int n; (n = inputStream.read(b)) != -1; ) {
              out.append(new String(b, 0, n));
            }
            return out.toString();
          }
        }
      } catch (Exception e) {
        log.error("post exception,param:{}", postParam, e);
      } finally {
        try {
          if (httpResponse != null) {
            httpResponse.disconnect();
          }
        } catch (Exception e) {
          log.error("httpResponse disconnect exception", e);
        }
      }
      return null;
    }
   
    @PreDestroy
    public static void destory() {
      try {
        log.info("httpTransport shutdown now....");
        httpTransport.shutdown();
      } catch (IOException e) {
        log.error("shut down httpTransport exception", e);
      }
    }
   
  }

• 如果想使用上面的 HttpClientUtils，必须引入 google-httpclient:

  •  　　<dependency>
            <groupId>com.google.http-client</groupId>
            <artifactId>google-http-client</artifactId>
            <version>1.22.0</version>
          </dependency>