Avoid gpg signing prompt when using Maven release plugin

Just set it up in a profile in settings.xml and activate it by default:

<settings>
  <profiles>
    <profile>
      <id>gpg</id>
      <properties>
        <gpg.executable>gpg2</gpg.executable>
        <gpg.passphrase>mypassphrase</gpg.passphrase>
      </properties>
    </profile>
  </profiles>
  <activeProfiles>
    <activeProfile>gpg</activeProfile>
  </activeProfiles>
</settings>

As you can see you can do that with any property .. e.g. also other usernames and passwords for the jarsigner plugin and so on.

This should be always active. It might depend on using a newer Maven version but you can always debug this with

mvn help:active-profiles

Encrypting the password

The comments and other answers are pointing out that keeping passwords in a file is not secure… This is true to an extent, but luckily Maven allows us to make this very secure by creating one master password and then encrypting all the passwords in settings.xml with it.

Have a look at the mini guide Password Encryption for details.