配置使用连接池的httpClient

httpclient版本：

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.1</version>
</dependency>

spring配置如下:

<bean id="pollingConnectionManager"
  class="org.apache.http.impl.conn.PoolingHttpClientConnectionManager">
    <property name="maxTotal" value="10" />
    <property name="defaultMaxPerRoute" value="5" />
  </bean>

  <bean id="httpClientBuilder" class="org.apache.http.impl.client.HttpClientBuilder"
  factory-method="create">
    <property name="connectionManager" ref="pollingConnectionManager" />
  </bean>

  <bean id="httpClient" factory-bean="httpClientBuilder"
  factory-method="build" />

  <!-- -->
  <bean id="clientHttpRequestFactory"
  class="org.springframework.http.client.HttpComponentsClientHttpRequestFactory">
    <constructor-arg ref="httpClient" />
    <property name="connectTimeout" value="30000" />
    <property name="readTimeout" value="30000" />
  </bean>

配置带有连接池的org.springframework.web.client.RestTemplate

<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
    <constructor-arg ref="clientHttpRequestFactory" />
    <property name="messageConverters">
      <list>
        <bean      class="org.springframework.http.converter.StringHttpMessageConverter" />
        <bean      class="org.springframework.http.converter.xml.SourceHttpMessageConverter" />
        <bean class="org.springframework.http.converter.FormHttpMessageConverter" />
        <bean      class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter" />
        <bean      class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter" />
      </list>
    </property>
  </bean>

基于注解的httpclient配置，在带有@Configuration的类中编写如下代码：

  @Bean(name = "poolingHttpClientConnectionManager")
    public PoolingHttpClientConnectionManager poolingHttpClientConnectionManager() {
        PoolingHttpClientConnectionManager poolingHttpClientConnectionManager = new PoolingHttpClientConnectionManager();
        poolingHttpClientConnectionManager.setMaxTotal(10);
        poolingHttpClientConnectionManager.setDefaultMaxPerRoute(5);
        return poolingHttpClientConnectionManager;
    }

    @Bean(name = "httpClientBuilder")
    public HttpClientBuilder httpClientBuilder() {
        HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
        httpClientBuilder.setConnectionManager(poolingHttpClientConnectionManager());
        return httpClientBuilder;
    }


    @Bean(name = "httpClient")
    public CloseableHttpClient httpClient() {

        return httpClientBuilder().build();

    }