2 way TLS (1.2) between Java client and Apple pay server - java-8

Question

Trying to achieve:
As required in Apple Pay for Web, 2 way TLS 1.2 is required. In my case i'm trying to hit apple pay server from my java with json payload (which you can say as client).
https://developer.apple.com/reference/applepayjs/applepaysession#2166532
My points of Concern:
1) Any command that list all the cipher suites supported? running on java 1.8.
2) What is required while making HttpsURLconnection.openconnection to be TLS1.2?
3) Any example code by which i can achieve this connection.
4) What are the settings required like certificate and private key?
Any help would be useful.
I know i have asked very direct questions, but i will keep adding more specific questions in this.
Update: First 3 points are done.
Now only Regarding point 4: I'm sending both the files key and cert by converting to cert.p12 file and saving as new keystore.
openssl x509 -inform der -in merchant_id.cer -out merchant_id.pem
openssl pkcs12 -nodes -export -in merchant_id.pem -inkey clientprivate.key -out cert.p12 -name "Certificate"
After that running java code with VM arguments in eclipse:
-Djavax.net.ssl.keyStoreType=pkcs12 -Djavax.net.ssl.keyStore=cert.p12 -Djavax.net.debug=ssl
I can see following error in console:
*ServerHelloDone
Warning: no suitable certificate found - continuing without client authentication
* Certificate chain
** ECDHClientKeyExchange
main, WRITE: TLSv1.2 Change Cipher Spec, length = 1
*** Finished
verify_data:
*
main, WRITE: TLSv1.2 Handshake, length = 64
main, handling exception: java.net.SocketException: Connection reset
%% Invalidated: [Session-1, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA]
main, SEND TLSv1.2 ALERT: fatal, description = unexpected_message
main, WRITE: TLSv1.2 Alert, length = 48
main, Exception sending alert: java.net.SocketException: Connection reset by peer: socket write error
main, called closeSocket()
java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at sun.security.ssl.InputRecord.readFully(Unknown Source)
at sun.security.ssl.InputRecord.read(Unknown Source)
at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
at sun.net.www.protocol.https.HttpsClient.afterConnect(Unknown Source)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(Unknown Source)
Here is the java code:
HttpsURLConnection conn = (HttpsURLConnection)url.openConnection();
conn.setSSLSocketFactory(factory);
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
conn.setRequestProperty("Accept", "application/json");
conn.setRequestMethod("POST");
OutputStream os = conn.getOutputStream();
os.write(jsonInString.getBytes("UTF-8"));
Failing at
conn.getOutputStream();
Using java 1.8

Answer 1

General answers in the order asked..
I found this very helpful to list all ciphers: https://confluence.atlassian.com/stashkb/list-ciphers-used-by-jvm-679609085.html
I used this System.setProperty("https.protocols", "TLSv1.2"); to set it to TLS 1.2.
I can't post my whole project here its too much code... It's a basic http request with all required fields sent along.
First create an "apple pay merchant id" certificate on apple's website, download it, extract the certificate and the key from it into 2 separate files, send both along with your request (with the password, of course).