How can I create keystore from an existing certificate (abc.crt) and abc.key files?

Adding to @MK Yung and @Bruno's answer.. Do enter a password for the destination keystore. I saw my console hanging when I entered the command without a password.

openssl pkcs12 -export -in abc.crt -inkey abc.key -out abc.p12 -name localhost  -passout pass:changeit

In addition to @Bruno's answer, you need to supply the -name for alias, otherwise Tomcat will throw Alias name tomcat does not identify a key entry error

Sample Command: openssl pkcs12 -export -in localhost.crt -inkey localhost.key -out localhost.p12 -name localhost

Ideally you should have received 3 files: ca_bundle.crt yourname.crt yourname.key

Use the following command to create the pk cs 12 version of it with:

openssl pkcs12 -export -out yourname.pfx -inkey yourname.key -in yourname.crt -certfile ca_bundle.crt

Then you will need to import it into key store that is easy to configure in Apache

keytool -importkeystore -srckeystore yourname.pfx -srcstorepass yourpassword -srcstoretype pkcs12 -destkeystore yourkeystore.jks -deststoretype jks -deststorepass yourkeystorepassword

If the keystore is for tomcat then, after creating the keystore with the above answers, you must add a final step to create the "tomcat" alias for the key:

keytool -changealias -alias "1" -destalias "tomcat" -keystore keystore-file.jks

You can check the result with:

keytool -list -keystore keystore-file.jks -v