Spring Boot 使用RestTemplate-02-使用OkHttp

一、简介

OkHttp是一个高效的HTTP客户端，容许全部同一个主机地址的请求共享同一个socket链接；链接池减小请求延时；透明的GZIP压缩减小响应数据的大小；缓存响应内容，避免一些彻底重复的请求

当网络出现问题的时候OkHttp依然坚守本身的职责，它会自动恢复通常的链接问题，若是你的服务有多个IP地址，当第一个IP请求失败时，OkHttp会交替尝试你配置的其余IP，OkHttp使用现代TLS技术(SNI, ALPN)初始化新的链接，当握手失败时会回退到TLS 1.0。

1）使用：它的请求/响应 API 使用构造器模式builders来设计，它支持阻塞式的同步请求和带回调的异步请求。

<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>3.10.0</version>
</dependency>

import okhttp3.ConnectionPool;
import okhttp3.OkHttpClient;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.ClientHttpRequestFactory;
import org.springframework.http.client.OkHttp3ClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.concurrent.TimeUnit;

@Configuration
public class OkHttpRestTemplateConfig {


    @Bean("okHttpRestTemplate")
    public RestTemplate okHttpRestTemplate() {
        OkHttpClient httpClient = okHttpClient();
        ClientHttpRequestFactory factory = new OkHttp3ClientHttpRequestFactory(httpClient);
        RestTemplate restTemplate = new RestTemplate(factory);
        // 能够添加消息转换
        //restTemplate.setMessageConverters(...);
        // 能够增长拦截器
        //restTemplate.setInterceptors(...);
        return restTemplate;
    }

    @Bean
    public OkHttpClient okHttpClient() {
        return new OkHttpClient.Builder()
                //.sslSocketFactory(sslSocketFactory(), x509TrustManager())
                .retryOnConnectionFailure(false)
                .connectionPool(pool())
                .connectTimeout(30, TimeUnit.SECONDS)
                .readTimeout(30, TimeUnit.SECONDS)
                .writeTimeout(30,TimeUnit.SECONDS)
                .build();
    }

    @Bean
    public X509TrustManager x509TrustManager() {
        return new X509TrustManager() {
            @Override
            public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
            }
            @Override
            public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException {
            }
            @Override
            public X509Certificate[] getAcceptedIssuers() {
                return new X509Certificate[0];
            }
        };
    }

    @Bean
    public SSLSocketFactory sslSocketFactory() {
        try {
            //信任任何连接
            SSLContext sslContext = SSLContext.getInstance("TLS");
            sslContext.init(null, new TrustManager[]{x509TrustManager()}, new SecureRandom());
            return sslContext.getSocketFactory();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        }
        return null;
    }

    /**
     * Create a new connection pool with tuning parameters appropriate for a single-user application.
     * The tuning parameters in this pool are subject to change in future OkHttp releases. Currently
     */
    @Bean
    public ConnectionPool pool() {
        return new ConnectionPool(200, 5, TimeUnit.MINUTES);
    }
}