Common configuration - Encrypted communication

可以通过HttpClientConfigCallback配置加密传输。 参数org.apache.http.impl.nio.client.HttpAsyncClientBuilder 公开了多个方法来配置加密传输：setSSLContext，setSSLSessionStrategy和setConnectionManager，以下是一个例子：

KeyStore truststore = KeyStore.getInstance("jks");
try (InputStream is = Files.newInputStream(keyStorePath)) {
    truststore.load(is, keyStorePass.toCharArray());
}
SSLContextBuilder sslBuilder = SSLContexts.custom().loadTrustMaterial(truststore, null);
final SSLContext sslContext = sslBuilder.build();
RestClientBuilder builder = RestClient.builder(new HttpHost("localhost", 9200, "https"))
        .setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
            @Override
            public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
                return httpClientBuilder.setSSLContext(sslContext);
            }
        });

如果没有提供明确的配置，则使用系统默认配置。