keytool -export -alias tomcat  -keystore <you jks>wsriakey.keystore -file <outputfile>wsriakey.crt

openssl x509 -out <outputfilename>wsriakey-pem.crt -outform pem -text -in <some crt you want to use>wsriakey.crt -inform der

使用Java 代码

git clone https://github.com/joshvette001/java-exportpriv.git

cd java-exportpriv.git

javac ExportPriv.java

java ExportPriv <keystore> <alias> <password> > wsriakey-pkcs8.key

openssl pkcs8 -inform PEM -nocrypt -in wsriakey-pkcs8.key -out <you private key>wsriakey.keyitclj.key

https://github.com/joshvette001/java-exportpriv.git
https://myssl.com/
https://mozilla.github.io/server-side-tls/ssl-config-generator/