httpclient封装了java中进行http网络请求的底层实现，是一个被广泛使用的组件。

httpclient是支持池化机制的，这两个参数就是表示池化设置的。

服务之间发送http请求常用的有Apache的Fluent以及spring的restTemplate等

Apache的Fluent，以及spring的restTemplate都是对httpclient进行了封装

以Apache的Fluent为例说明

其Executor类

/**

 * An Executor for fluent requests

 * <p/>

 * A {@link PoolingHttpClientConnectionManager} with maximum 100 connections per route and

 * a total maximum of 200 connections is used internally.

 */

最大100 connections per route 以及 最大200个 connection

CONNMGR = new PoolingHttpClientConnectionManager(sfr);

CONNMGR.setDefaultMaxPerRoute(100);

CONNMGR.setMaxTotal(200);

CLIENT = HttpClientBuilder.create().setConnectionManager(CONNMGR).build();

其代码中是写死的

这两个参数的含义是什么呢？

下面用测试代码说明一下

测试端

public class HttpFluentUtil {

    private Logger logger = LoggerFactory.getLogger(HttpFluentUtil.class);

    private final static int MaxPerRoute = 2;

    private final static int MaxTotal = 4;



    final static PoolingHttpClientConnectionManager CONNMGR;

    final static HttpClient CLIENT;

    final static Executor EXECUTOR;



    static {

        LayeredConnectionSocketFactory ssl = null;

        try {

            ssl = SSLConnectionSocketFactory.getSystemSocketFactory();

        } catch (final SSLInitializationException ex) {

            final SSLContext sslcontext;

            try {

                sslcontext = SSLContext.getInstance(SSLConnectionSocketFactory.TLS);

                sslcontext.init(null, null, null);

                ssl = new SSLConnectionSocketFactory(sslcontext);

            } catch (final SecurityException ignore) {

            } catch (final KeyManagementException ignore) {

            } catch (final NoSuchAlgorithmException ignore) {

            }

        }



        final Registry<ConnectionSocketFactory> sfr = RegistryBuilder.<ConnectionSocketFactory>create()

                .register("http", PlainConnectionSocketFactory.getSocketFactory())

                .register("https", ssl != null ? ssl : SSLConnectionSocketFactory.getSocketFactory()).build();



        CONNMGR = new PoolingHttpClientConnectionManager(sfr);

        CONNMGR.setDefaultMaxPerRoute(MaxPerRoute);

        CONNMGR.setMaxTotal(MaxTotal);

        CLIENT = HttpClientBuilder.create().setConnectionManager(CONNMGR).build();

        EXECUTOR = Executor.newInstance(CLIENT);

    }



    public static String Get(String uri, int connectTimeout, int socketTimeout) throws IOException {

        return EXECUTOR.execute(Request.Get(uri).connectTimeout(connectTimeout).socketTimeout(socketTimeout))

                .returnContent().asString();

    }



    public static String Post(String uri, StringEntity stringEntity, int connectTimeout, int socketTimeout)

            throws IOException {

        return EXECUTOR.execute(Request.Post(uri).socketTimeout(socketTimeout)

                .addHeader("Content-Type", "application/json").body(stringEntity)).returnContent().asString();

    }





    public static void main(String[] args) {

        HttpUtil httpUtil = new HttpUtil();

        String url = "http://localhost:9064/app/test"; // 服务端sleep 5秒再返回

        for (int i = 0; i < 5; i++) { // MaxPerRoute若设置为2，则5线程分3组返回（2、2、1），共15秒

            new Thread(new Runnable() {



                @Override

                public void run() {

                    try {

                        String result = HttpFluentUtil.Get(url, 2000, 2000);

                        System.out.println(result);

                    } catch (IOException e) {

                        e.printStackTrace();

                    }



                }

            }).start();

        }



    }



}

服务器端

很简单的springmvc

@GetMapping(value="test")

public String test() throws InterruptedException {

    Thread.sleep(1000);

    return "1";

}

测试1：测试端MaxPerRoute=5 MaxTotal=4

服务器端结果

可以看到先接收4个请求，处理完成后，再接收下一次剩余的1个请求。即其一次最多接收MaxTotal次请求

测试2：测试端MaxPerRoute=2 MaxTotal=5

服务器端结果

可以看到接收2个请求，2个请求，1个请求，即说明maxPerRoute意思是某一个服务每次能并行接收的请求数量

什么场景下要设置？

知道了两个参数的含义，那么在什么情况下要对这两个参数进行设置呢？

比如说下面的场景

服务1要通过Fluent调用服务2的接口。服务1发送了400个请求，但由于Fluent默认只支持maxPerRoute=100，MaxTotal=200，比如接口执行时间为500ms，由于maxPerRoute=100，所以要分为100,100,100,100分四批来执行，全部执行完成需要2000ms。而如果maxPerRoute设置为400，全部执行完需要500ms。在这种情况下（提供并发能力时）就要对这两个参数进行设置了。

设置的方法

Apache Fluent可以使用上面测试的HttpFluentUtil工具类来执行请求

RestTemplate类似使用下面的方式

@Bean

public HttpClient httpClient() {

   Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()

            .register("http", PlainConnectionSocketFactory.getSocketFactory())

            .register("https", SSLConnectionSocketFactory.getSocketFactory())

            .build();

    PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);

    connectionManager.setMaxTotal(restTemplateProperties.getMaxTotal());

    connectionManager.setDefaultMaxPerRoute(restTemplateProperties.getDefaultMaxPerRoute());

    connectionManager.setValidateAfterInactivity(restTemplateProperties.getValidateAfterInactivity());

    RequestConfig requestConfig = RequestConfig.custom()

            .setSocketTimeout(restTemplateProperties.getSocketTimeout())

            .setConnectTimeout(restTemplateProperties.getConnectTimeout())

            .setConnectionRequestTimeout(restTemplateProperties.getConnectionRequestTimeout())

            .build();

    return HttpClientBuilder.create()

            .setDefaultRequestConfig(requestConfig)

            .setConnectionManager(connectionManager)

            .build();

   

}

@Bean

public ClientHttpRequestFactory httpRequestFactory() {

    return new HttpComponentsClientHttpRequestFactory(httpClient());

}

@Bean

   public RestTemplate restTemplate() {

       return new RestTemplate(httpRequestFactory());

   }

其中RestTemplateProperties通过配置文件来配置

max-total

default-max-per-route

connect-timeout  获取连接超时

connection-request-timeout  请求超时

socket-timeout  读超时