title: how to use environment variable in spring boot properties
body: <p>i have an app with spring boot that i want to connect to sqlite database in that path C:\Users\user7\AppData\Roaming.
  what i have to write on the app.properties to indicate environment variable APPDATA path?
  this is my app.properties</p>
  <pre><code>spring.datasource.url = jdbc:sqlite:sqlitesample.db
  </code></pre>
  <p>how to use APPDATA variable?
  regards</p>