System.setProperty("javax.net.debug", "all");

adding as trusted cert:
 Subject: CN=Entrust.net Certification Authority (2048), OU=(c)    1999   Entrust.net Limited, OU=www.entrust.net/CPS_2048 incorp. by ref. (limits liab.), O=Entrust.net
 Issuer:  CN=Entrust.net Certification Authority (2048), OU=(c) 1999 Entrust.net Limited, OU=www.entrust.net/CPS_2048 incorp. by ref. (limits liab.), O=Entrust.net
 Algorithm: RSA; Serial number: 0x3863def8
 Valid from Fri Dec 24 12:50:51 EST 1999 until Tue Jul 24 10:15:12 EDT 2029

main, READ: TLSv1 Handshake, length = 2649
*** Certificate chain
chain [0] =   [0]         Version: 3
     SerialNumber: 1356119177
       IssuerDN: C=US,O=Entrust, Inc.,OU=See www.entrust.net/legal-terms,OU=(c) 2012 Entrust, Inc. - for authorized use only,CN=Entrust Certification Authority - L1K
       Start Date: Wed Jul 15 11:50:20 EDT 2015
       Final Date: Sun Jul 15 18:27:04 EDT 2018

***
Caught: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException:
PKIX path building failed: java.security.cert.CertPathBuilderException:
No issuer certificate for certificate in certification path found.
main, SEND TLSv1 ALERT:  fatal, description = certificate_unknown

private class TrustAll implements X509TrustManager
{
    public void checkClientTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException
{
}

public void checkServerTrusted(X509Certificate[] x509Certificates, String s) throws CertificateException
{
}

public X509Certificate[] getAcceptedIssuers()
{
    return new X509Certificate[0];
}

TrustManager[] trustArray = [new TrustAll()] as TrustManager[]
SSLContext ctx = SSLContext.getInstance("TLSv1");
ctx.init(null, trustArray, null);

// create an http client builder
HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();
 httpClientBuilder.setSslcontext(ctx)

 httpclient = httpClientBuilder.build();