Resolve the hostname in Java code and use it

I am connecting to a service through my Java code. Let's call FQDN or hostname of service as: abc.xyz.com.

My Java implementation returns exception:

java.net.UnknownHostException: dfour6gtsg5a.streaming.us-phoenix-1.oci.oraclecloud.com
	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:567)
	at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:327)
	at java.base/java.net.Socket.connect(Socket.java:633)
	at java.base/sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:304)
	at java.base/sun.security.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:174)
	at java.base/sun.net.NetworkClient.doConnect(NetworkClient.java:183)
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:532)
	at java.base/sun.net.www.http.HttpClient.openServer(HttpClient.java:637)
	at java.base/sun.net.www.protocol.https.HttpsClient.<init>(HttpsClient.java:266)
	at java.base/sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:380)
	at 

Now, when I include entry of FQDN of service and IPAddress in /etc/hosts as below:

127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
...
100.70.125.57 abc.xyz.com

Same Java implementation works correctly as service FQDN get resolved to IP address correctly.

If I try to run Java implementation with IPAddress, I get below error:

javax.net.ssl.SSLHandshakeException: No subject alternative names matching IP address 100.70.125.57 found
	at java.base/sun.security.ssl.Alert.createSSLException(Alert.java:131)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:371)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:314)
	at java.base/sun.security.ssl.TransportContext.fatal(TransportContext.java:309)
	at java.base/sun.security.ssl.CertificateMessage$T12CertificateConsumer.checkServerCerts(CertificateMessage.java:654)
	at java.base/sun.security.ssl.CertificateMessage$T12CertificateConsumer.onCertificate(CertificateMessage.java:473)
	at java.base/sun.security.ssl.CertificateMessage$T12CertificateConsumer.consume(CertificateMessage.java:369)
	at java.base/sun.security.ssl.SSLHandshake.consume(SSLHandshake.java:396)

In production environment, I will not have access to /etc/hosts for editing.

How can I resolve the Service FQDN to the IPAddress inside my Java implementation?

The simplest way I found is to provide value true to HttpsURLConnection.setHostnameVerifier()

You need to override the method public boolean verify(String hostname, SSLSession session) for returning true everytime.

Below is an example:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.lang.Exception;
import java.net.URL;
import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLSession;
public class SkipVerification implements Runnable {
private static final String TAG = SkipVerification.class.toString();
private String server_port;
private String serverIP;
public SkipVerification(String serverIP, String server_port){
this.serverIP = serverIP;
this.server_port = server_port;
}
public void run() {
try {
HostnameVerifier hostnameVerifier = new HostnameVerifier() {
@Override
public boolean verify(String hostname, SSLSession session) {
return true;
}
};
URL url = new URL("https://" + serverIP + ":" + server_port + "/json");
InputStream inStream = null;
try {
HttpsURLConnection urlConnection = (HttpsURLConnection)url.openConnection();
urlConnection.setRequestProperty("Content-Type", "application/json");
urlConnection.setHostnameVerifier(hostnameVerifier);
inStream = urlConnection.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inStream));
} catch (Exception e) {
Log.e(TAG, "error fetching data from server", e);
} finally {
if (inStream != null) {
inStream.close();
}
}
} catch (Exception e) {
Log.e(TAG, "error initializing SkipVerificationn thread", e);
}
}
}

This works when using HttpsURLConnection class. For other implementation, please refer to comment to question by @Elliott Frisch.