Spring Boot 使用RestTemplate-02-使用OkHttp

一、簡介

OkHttp是一個高效的HTTP客戶端，容許全部同一個主機地址的請求共享同一個socket鏈接；鏈接池減小請求延時；透明的GZIP壓縮減小響應數據的大小；緩存響應內容，避免一些徹底重複的請求

當網絡出現問題的時候OkHttp依然堅守本身的職責，它會自動恢復通常的鏈接問題，若是你的服務有多個IP地址，當第一個IP請求失敗時，OkHttp會交替嘗試你配置的其餘IP，OkHttp使用現代TLS技術(SNI, ALPN)初始化新的鏈接，當握手失敗時會回退到TLS 1.0。

1）使用：它的請求/響應 API 使用構造器模式builders來設計，它支持阻塞式的同步請求和帶回調的異步請求。

<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);
        // 能夠添加消息轉換
        //restTemplate.setMessageConverters(...);
        // 能夠增長攔截器
        //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 {
            //信任任何連接
            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);
    }
}