封装了对 HTTP 请求的各种操作

使用 RestTemplate 可以方便地与 RESTful 服务进行交互，例如调用远程接口、访问 Web 服务、获取和发送数据等。

标准模板

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration(proxyBeanMethods = false)
public class RestTemplateConfiguration {

	@Bean
	public RestTemplate restTemplate() {
		return new RestTemplate();
	}

	@Bean  
	public ClientHttpRequestFactory clientHttpRequestFactory() {  
	    SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory()   ;  
	    // 连接超时时间10s  
	    factory.setConnectTimeout(10000);  
	    // 读取超时时间10s  
	    factory.setReadTimeout(10000);  
	    return factory;  
	}
}

模板2

import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig {


    @Bean
    public RestTemplate restTemplate(ClientHttpRequestFactory requestFactory){
        return new RestTemplate(requestFactory);
    }


    @Bean
    public ClientHttpRequestFactory httpRequestFactory(){
       return new HttpComponentsClientHttpRequestFactory(httpClient());
    }

    @Bean
    public HttpClient httpClient(){


        Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory>create()
                .register("http", PlainConnectionSocketFactory.getSocketFactory())
                .register("https", SSLConnectionSocketFactory.getSocketFactory())
                .build();

        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager(registry);


        //设置连接池最大是500个连接
        connectionManager.setMaxTotal(500);
        //MaxPerRoute是对maxtotal的细分，每个主机的并发最大是300，route是指域名
        connectionManager.setDefaultMaxPerRoute(300);
        /**
         * 只请求 xdclass.net,最大并发300
         *
         * 请求 xdclass.net,最大并发300
         * 请求 open1024.com,最大并发200
         *
         * //MaxtTotal=400 DefaultMaxPerRoute=200
         * //只连接到http://xdclass.net时，到这个主机的并发最多只有200；而不是400；
         * //而连接到http://xdclass.net 和 http://open1024.com时，到每个主机的并发最多只有200；
         * // 即加起来是400（但不能超过400）；所以起作用的设置是DefaultMaxPerRoute。
         *
         */

        RequestConfig requestConfig = RequestConfig.custom()
                //返回数据的超时时间
                .setSocketTimeout(20000)
                //连接上服务器的超时时间
                .setConnectTimeout(10000)
                //从连接池中获取连接的超时时间
                .setConnectionRequestTimeout(1000)
                .build();


        CloseableHttpClient closeableHttpClient = HttpClientBuilder.create().setDefaultRequestConfig(requestConfig)
                .setConnectionManager(connectionManager)
                .build();

        return closeableHttpClient;
    }
}