Lately I’ve been digging into Spring Security by reading a book “Spring Security in Action” by Laurentiu Spilca.

In the 2nd chapter we are given an example of how to use HTTPS with spring boot:

  1. Generate a certificate: openssl req -newkey rsa:2048 -x509 -keyout key.pem -out cert.pem -days 365

  2. Convert it to ‘p12’ format: openssl pkcs12 -export -in cert.pem -inkey key.pem -out certificate.p12 -name "certificate"

  3. Copy the generated ‘certificate.p12’ file inside ‘src/main/resources’ directory.

  4. Update ‘’:


One problem with this approach is that such certificates are not recognized by browsers, which will show an indicator that “this certificate is not trustworthy”.

An easy workaround involves using a tool mkcert:

With simple installation for macOS as an example:

# Install
brew install mkcert
brew install nss # if you use Firefox

# Setup local certificate authority (CA)
mkcert -install

# Generate certificate
mkcert -pkcs12 localhost

This will generate a new p12 (‘localhost+2.p12’) certificate for localhost and in current directory that will be registered in local certificate authority (CA) which will keep browsers happy when doing local development.

The rest of the steps is the same, copy into ‘src/main/resources’ and update ‘’.