超文本传输安全协议（英语：Hypertext Transfer Protocol Secure，缩写：HTTPS，也被称为HTTP over TLS，HTTP over SSL或HTTP Secure）是一种网络安全传输协议。

OkHttp：Java 平台上的新一代 HTTP 客户端

安卓官方文档 https://developer.android.google.cn/develop/index.html

Chrome 中通过 HTTPS 加载的页面百分比

一个 HTTPS 示例

假设您有一个由知名 CA 发放证书的网络服务器，那么，您可以使用如下简单代码发起安全的请求：

URL url = new URL("https://wikipedia.org");
URLConnection urlConnection = url.openConnection();
InputStream in = urlConnection.getInputStream();
copyInputStreamToOutputStream(in, System.out);

使用未知的证书颁发机构或者自签署的服务器证书可以参考官方文档，中文的哟
https://developer.android.google.cn/training/articles/security-ssl.html

Retrofit OkHttp HTTPS

官方 WIKI 关于使用 HTTPS 的介绍 https://github.com/square/okhttp/wiki/HTTPS

Show Code CustomTrust

import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.util.Arrays;
import java.util.Collection;

import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

import okhttp3.CertificatePinner;
import okio.Buffer;

public final class CustomTrust {

    public final X509TrustManager trustManager;
    public final SSLSocketFactory sslSocketFactory;

    public CustomTrust() {
        try {
            trustManager = trustManagerForCertificates(trustedCertificatesInputStream());
            SSLContext sslContext = SSLContext.getInstance("TLS");
            sslContext.init(null, new TrustManager[]{trustManager}, null);
            sslSocketFactory = sslContext.getSocketFactory();
        } catch (GeneralSecurityException e) {
            throw new RuntimeException(e);
        }
    }

    /**
    * Returns an input stream containing one or more certificate PEM files. This implementation just
    * embeds the PEM files in Java strings; most applications will instead read this from a resource
    * file that gets bundled with the application.
    */
    private InputStream trustedCertificatesInputStream() {
        // PEM files for root certificates of Comodo and Entrust. These two CAs are sufficient to view
        // https://publicobject.com (Comodo) and https://squareup.com (Entrust). But they aren't
        // sufficient to connect to most HTTPS sites including https://godaddy.com and https://visa.com.
        // Typically developers will need to get a PEM file from their organization's TLS administrator.
        String comodoRsaCertificationAuthority = ""
                + "-----BEGIN CERTIFICATE-----\n"
                + "MIIF2DCCA8CgAwIBAgIQTKr5yttjb+Af907YWwOGnTANBgkqhkiG9w0BAQwFADCB\n"
                + "hTELMAkGA1UEBhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4G\n"
                + "A1UEBxMHU2FsZm9yZDEaMBgGA1UEChMRQ09NT0RPIENBIExpbWl0ZWQxKzApBgNV\n"
                + "BAMTIkNPTU9ETyBSU0EgQ2VydGlmaWNhdGlvbiBBdXRob3JpdHkwHhcNMTAwMTE5\n"
                + "MDAwMDAwWhcNMzgwMTE4MjM1OTU5WjCBhTELMAkGA1UEBhMCR0IxGzAZBgNVBAgT\n"
                + "EkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMR\n"
                + "Q09NT0RPIENBIExpbWl0ZWQxKzApBgNVBAMTIkNPTU9ETyBSU0EgQ2VydGlmaWNh\n"
                + "dGlvbiBBdXRob3JpdHkwggIiMA0GCSqGSIb3DQEBAQUAA4ICDwAwggIKAoICAQCR\n"
                + "6FSS0gpWsawNJN3Fz0RndJkrN6N9I3AAcbxT38T6KhKPS38QVr2fcHK3YX/JSw8X\n"
                + "pz3jsARh7v8Rl8f0hj4K+j5c+ZPmNHrZFGvnnLOFoIJ6dq9xkNfs/Q36nGz637CC\n"
                + "9BR++b7Epi9Pf5l/tfxnQ3K9DADWietrLNPtj5gcFKt+5eNu/Nio5JIk2kNrYrhV\n"
                + "/erBvGy2i/MOjZrkm2xpmfh4SDBF1a3hDTxFYPwyllEnvGfDyi62a+pGx8cgoLEf\n"
                + "Zd5ICLqkTqnyg0Y3hOvozIFIQ2dOciqbXL1MGyiKXCJ7tKuY2e7gUYPDCUZObT6Z\n"
                + "+pUX2nwzV0E8jVHtC7ZcryxjGt9XyD+86V3Em69FmeKjWiS0uqlWPc9vqv9JWL7w\n"
                + "qP/0uK3pN/u6uPQLOvnoQ0IeidiEyxPx2bvhiWC4jChWrBQdnArncevPDt09qZah\n"
                + "SL0896+1DSJMwBGB7FY79tOi4lu3sgQiUpWAk2nojkxl8ZEDLXB0AuqLZxUpaVIC\n"
                + "u9ffUGpVRr+goyhhf3DQw6KqLCGqR84onAZFdr+CGCe01a60y1Dma/RMhnEw6abf\n"
                + "Fobg2P9A3fvQQoh/ozM6LlweQRGBY84YcWsr7KaKtzFcOmpH4MN5WdYgGq/yapiq\n"
                + "crxXStJLnbsQ/LBMQeXtHT1eKJ2czL+zUdqnR+WEUwIDAQABo0IwQDAdBgNVHQ4E\n"
                + "FgQUu69+Aj36pvE8hI6t7jiY7NkyMtQwDgYDVR0PAQH/BAQDAgEGMA8GA1UdEwEB\n"
                + "/wQFMAMBAf8wDQYJKoZIhvcNAQEMBQADggIBAArx1UaEt65Ru2yyTUEUAJNMnMvl\n"
                + "wFTPoCWOAvn9sKIN9SCYPBMtrFaisNZ+EZLpLrqeLppysb0ZRGxhNaKatBYSaVqM\n"
                + "4dc+pBroLwP0rmEdEBsqpIt6xf4FpuHA1sj+nq6PK7o9mfjYcwlYRm6mnPTXJ9OV\n"
                + "2jeDchzTc+CiR5kDOF3VSXkAKRzH7JsgHAckaVd4sjn8OoSgtZx8jb8uk2Intzna\n"
                + "FxiuvTwJaP+EmzzV1gsD41eeFPfR60/IvYcjt7ZJQ3mFXLrrkguhxuhoqEwWsRqZ\n"
                + "CuhTLJK7oQkYdQxlqHvLI7cawiiFwxv/0Cti76R7CZGYZ4wUAc1oBmpjIXUDgIiK\n"
                + "boHGhfKppC3n9KUkEEeDys30jXlYsQab5xoq2Z0B15R97QNKyvDb6KkBPvVWmcke\n"
                + "jkk9u+UJueBPSZI9FoJAzMxZxuY67RIuaTxslbH9qh17f4a+Hg4yRvv7E491f0yL\n"
                + "S0Zj/gA0QHDBw7mh3aZw4gSzQbzpgJHqZJx64SIDqZxubw5lT2yHh17zbqD5daWb\n"
                + "QOhTsiedSrnAdyGN/4fy3ryM7xfft0kL0fJuMAsaDk527RH89elWsn2/x20Kk4yl\n"
                + "0MC2Hb46TpSi125sC8KKfPog88Tk5c0NqMuRkrF8hey1FGlmDoLnzc7ILaZRfyHB\n"
                + "NVOFBkpdn627G190\n"
                + "-----END CERTIFICATE-----\n";
        String entrustRootCertificateAuthority = ""
                + "-----BEGIN CERTIFICATE-----\n"
                + "MIIEkTCCA3mgAwIBAgIERWtQVDANBgkqhkiG9w0BAQUFADCBsDELMAkGA1UEBhMC\n"
                + "VVMxFjAUBgNVBAoTDUVudHJ1c3QsIEluYy4xOTA3BgNVBAsTMHd3dy5lbnRydXN0\n"
                + "Lm5ldC9DUFMgaXMgaW5jb3Jwb3JhdGVkIGJ5IHJlZmVyZW5jZTEfMB0GA1UECxMW\n"
                + "KGMpIDIwMDYgRW50cnVzdCwgSW5jLjEtMCsGA1UEAxMkRW50cnVzdCBSb290IENl\n"
                + "cnRpZmljYXRpb24gQXV0aG9yaXR5MB4XDTA2MTEyNzIwMjM0MloXDTI2MTEyNzIw\n"
                + "NTM0MlowgbAxCzAJBgNVBAYTAlVTMRYwFAYDVQQKEw1FbnRydXN0LCBJbmMuMTkw\n"
                + "NwYDVQQLEzB3d3cuZW50cnVzdC5uZXQvQ1BTIGlzIGluY29ycG9yYXRlZCBieSBy\n"
                + "ZWZlcmVuY2UxHzAdBgNVBAsTFihjKSAyMDA2IEVudHJ1c3QsIEluYy4xLTArBgNV\n"
                + "BAMTJEVudHJ1c3QgUm9vdCBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTCCASIwDQYJ\n"
                + "KoZIhvcNAQEBBQADggEPADCCAQoCggEBALaVtkNC+sZtKm9I35RMOVcF7sN5EUFo\n"
                + "Nu3s/poBj6E4KPz3EEZmLk0eGrEaTsbRwJWIsMn/MYszA9u3g3s+IIRe7bJWKKf4\n"
                + "4LlAcTfFy0cOlypowCKVYhXbR9n10Cv/gkvJrT7eTNuQgFA/CYqEAOwwCj0Yzfv9\n"
                + "KlmaI5UXLEWeH25DeW0MXJj+SKfFI0dcXv1u5x609mhF0YaDW6KKjbHjKYD+JXGI\n"
                + "rb68j6xSlkuqUY3kEzEZ6E5Nn9uss2rVvDlUccp6en+Q3X0dgNmBu1kmwhH+5pPi\n"
                + "94DkZfs0Nw4pgHBNrziGLp5/V6+eF67rHMsoIV+2HNjnogQi+dPa2MsCAwEAAaOB\n"
                + "sDCBrTAOBgNVHQ8BAf8EBAMCAQYwDwYDVR0TAQH/BAUwAwEB/zArBgNVHRAEJDAi\n"
                + "gA8yMDA2MTEyNzIwMjM0MlqBDzIwMjYxMTI3MjA1MzQyWjAfBgNVHSMEGDAWgBRo\n"
                + "kORnpKZTgMeGZqTx90tD+4S9bTAdBgNVHQ4EFgQUaJDkZ6SmU4DHhmak8fdLQ/uE\n"
                + "vW0wHQYJKoZIhvZ9B0EABBAwDhsIVjcuMTo0LjADAgSQMA0GCSqGSIb3DQEBBQUA\n"
                + "A4IBAQCT1DCw1wMgKtD5Y+iRDAUgqV8ZyntyTtSx29CW+1RaGSwMCPeyvIWonX9t\n"
                + "O1KzKtvn1ISMY/YPyyYBkVBs9F8U4pN0wBOeMDpQ47RgxRzwIkSNcUesyBrJ6Zua\n"
                + "AGAT/3B+XxFNSRuzFVJ7yVTav52Vr2ua2J7p8eRDjeIRRDq/r72DQnNSi6q7pynP\n"
                + "9WQcCk3RvKqsnyrQ/39/2n3qse0wJcGE2jTSW3iDVuycNsMm4hH2Z0kdkquM++v/\n"
                + "eu6FSqdQgPCnXEqULl8FmTxSQeDNtGPPAUO6nIPcj2A781q0tHuu2guQOHXvgR1m\n"
                + "0vdXcDazv/wor3ElhVsT/h5/WrQ8\n"
                + "-----END CERTIFICATE-----\n";
        return new Buffer()
                .writeUtf8(comodoRsaCertificationAuthority)
                .writeUtf8(entrustRootCertificateAuthority)
                .inputStream();
    }

    /**
    * Returns a trust manager that trusts {@code certificates} and none other. HTTPS services whose
    * certificates have not been signed by these certificates will fail with a {@code
    * SSLHandshakeException}.
    * <p>
    * <p>This can be used to replace the host platform's built-in trusted certificates with a custom
    * set. This is useful in development where certificate authority-trusted certificates aren't
    * available. Or in production, to avoid reliance on third-party certificate authorities.
    * <p>
    * <p>See also {@link CertificatePinner}, which can limit trusted certificates while still using
    * the host platform's built-in trust store.
    * <p>
    * <h3>Warning: Customizing Trusted Certificates is Dangerous!</h3>
    * <p>
    * <p>Relying on your own trusted certificates limits your server team's ability to update their
    * TLS certificates. By installing a specific set of trusted certificates, you take on additional
    * operational complexity and limit your ability to migrate between certificate authorities. Do
    * not use custom trusted certificates in production without the blessing of your server's TLS
    * administrator.
    */
    private X509TrustManager trustManagerForCertificates(InputStream in)
            throws GeneralSecurityException {
        CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
        Collection<? extends Certificate> certificates = certificateFactory.generateCertificates(in);
        if (certificates.isEmpty()) {
            throw new IllegalArgumentException("expected non-empty set of trusted certificates");
        }

        // Put the certificates a key store.
        char[] password = "password".toCharArray(); // Any password will work.
        KeyStore keyStore = newEmptyKeyStore(password);
        int index = 0;
        for (Certificate certificate : certificates) {
            String certificateAlias = Integer.toString(index++);
            keyStore.setCertificateEntry(certificateAlias, certificate);
        }

        // Use it to build an X509 trust manager.
        KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance(
                KeyManagerFactory.getDefaultAlgorithm());
        keyManagerFactory.init(keyStore, password);
        TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(
                TrustManagerFactory.getDefaultAlgorithm());
        trustManagerFactory.init(keyStore);
        TrustManager[] trustManagers = trustManagerFactory.getTrustManagers();
        if (trustManagers.length != 1 || !(trustManagers[0] instanceof X509TrustManager)) {
            throw new IllegalStateException("Unexpected default trust managers:"
                    + Arrays.toString(trustManagers));
        }
        return (X509TrustManager) trustManagers[0];
    }

    private KeyStore newEmptyKeyStore(char[] password) throws GeneralSecurityException {
        try {
            KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
            InputStream in = null; // By convention, 'null' creates an empty key store.
            keyStore.load(in, password);
            return keyStore;
        } catch (IOException e) {
            throw new AssertionError(e);
        }
    }

}

构建客户端

static RequestService newClient() {
    CustomTrust ct = new CustomTrust();
    OkHttpClient client = new OkHttpClient.Builder()
            .addInterceptor(chain -> {
                // 请求头
                Request request = chain.request().newBuilder()
                        .addHeader("X-CRM-Application-Id", RequestConstants.APPLICATION_ID)
                        .addHeader("X-CRM-Version", RequestConstants.VERSION)
                        .addHeader("Content-Type", RequestConstants.JSON_TYPE)
                        .build();
                return chain.proceed(request);
            })
            // 超时时间
            .readTimeout(5, TimeUnit.MINUTES)
            .connectTimeout(5, TimeUnit.MINUTES)
            // HTTPS
            .sslSocketFactory(ct.sslSocketFactory, ct.trustManager)
            // Hostname domain.com not verified
            .hostnameVerifier((s, sslSession) -> true)
            .build();

    Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(RequestConstants.BASE_URL)
            .client(client)
             // FastJson
            .addConverterFactory(FastJsonConvertFactory.create())
             // RxJava2
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .build();

    return retrofit.create(RequestService.class);
}

参考资料：

• HTTP将被标为不安全
• 向越来越多的HTTPS致敬！
• OkHttp 示例代码