The reverse proxy approach does seem to be the most common option. However, as an 'experiment' I looked into using just ring, jetty compojure etc with https. It isn't that hard.
First you need to use keytool to generate a self signed certificate and install that into a new keystore. The keytool docs a pretty good and can walk you through this process. Note that if you use a self signed cert, you will need to add an exception rule with most browsers to say that you trust that certificate.
Copy the keystore file created into the root of your project tree
Update the jetty config parameters to specify ssl, ssl-port, keystore file and keystore password.
Add the ring/ring-defaults package to your project.clj
Add the wrap-defaults middleware with the secure-site-defaults configuration option to force https connections i.e. redirect http connections to https.
This is not the setup I would recommend for production use, but I found it simpler than also having to configure ngix when doing development etc. The hardest part was working through the keytool process. However, just following the docs and examples gives you enough provided you don't allow yoruself to be overwhelmed by all the options - just keep it simple.
Something like
keytool -genkeypair \
-keystore $SSL_DIR/$KS_NAME \
-keypass $PASSWORD \
-storepass $PASSWORD \
-keyalg RSA -keysize 2048 \
-alias root \
-ext bc:c \
-dname "$ROOT_CN"
echo "CA Key"
keytool -genkeypair \
-keystore $SSL_DIR/$KS_NAME \
-alias ca \
-ext bc:c \
-keypass $PASSWORD \
-keyalg RSA -keysize 2048 \
-storepass $PASSWORD \
-dname "$CA_CN"
echo "Server Key"
keytool -genkeypair \
-keystore $SSL_DIR/$KS_NAME \
-alias server \
-keypass $PASSWORD \
-storepass $PASSWORD \
-keyalg RSA -keysize 2048 \
-dname "$SERVER_CN"
echo "Root Cert"
keytool -keystore $SSL_DIR/$KS_NAME \
-storepass $PASSWORD \
-alias root \
-exportcert \
-rfc > $SSL_DIR/root.pem
echo "CA Cert"
keytool -storepass $PASSWORD \
-keystore $SSL_DIR/$KS_NAME \
-certreq \
-alias ca | keytool -storepass $PASSWORD \
-keystore $SSL_DIR/$KS_NAME \
-gencert \
-alias root \
-ext BC=0 \
-rfc > $SSL_DIR/ca.pem
echo "Import CA cert"
keytool -keystore $SSL_DIR/$KS_NAME \
-storepass $PASSWORD \
-importcert \
-alias ca \
-file $SSL_DIR/ca.pem
echo "Server Cert"
keytool -storepass $PASSWORD \
-keystore $SSL_DIR/$KS_NAME \
-certreq \
-alias server | keytool -storepass $PASSWORD \
-keystore $SSL_DIR/$KS_NAME \
-gencert \
-alias ca \
-rfc > $SSL_DIR/server.pem
echo "Import Server Cert"
cat $SSL_DIR/root.pem $SSL_DIR/ca.pem $SSL_DIR/server.pem | \
keytool -keystore $SSL_DIR/$KS_NAME \
-storepass $PASSWORD \
-keypass $PASSWORD \
-importcert \
-alias server