Change effective on 02 February 2017
Heroku’s support for Java will now set the
SPRING_DATASOURCE_URL environment variable for all Java apps using a SQL Database add-on. This environment variable may take precedence over existing configuration, which may cause unexpected database connection errors.
For more information see the Dev Center article Connecting to Relational Databases on Heroku with Java. For more information on Spring configuration see the Official Spring Documentation.