Importing private keys into a Java keystore using keytool
For ages the keytool application shipped as part of Java could provide all the functionality to generate a private key and certificate sign request from a Java keystore, but the most basic function, importing a preexisting private key and certificate generated externally, remained overlooked.
This is fixed in Java 6, at long last.
The solution is to convert your existing certificate and key into a PKCS12 file, and then use the keytool functionality to merge one keystore with another one. Java 6 can treat a PKCS12 file as a keystore, so putting this together, you get this:
keytool -importkeystore -deststorepass changeit -destkeypass changeit -destkeystore my-keystore.jks -srckeystore cert-and-key.p12 -srcstoretype PKCS12 -srcstorepass cert-and-key-password -alias 1
The alias of 1 is required to choose the certificate in the source PKCS12 file, keytool isn't clever enough to figure out which certificate you want in a store containing one certificate.
At last, it works.