I struggle on this for over 3 weeks. god...
Liferay CE 7.4.2 GA3
Oracle JDK 8
Liferay Developer Studio Version: 22.214.171.124108090632-ga5
sometime, we have to connect to another database for many reasons, system is old, they cannot provide web service..etc.
there have two ways for this purpose, DataSourceProvider and SpringBeans
1. before start, we have to download ojdbc.jar, because i use jdk8 and my target database is Oracle, so i need ojdbc8.jar, and put it on TOMCAT_HOME\webapps\ROOT\WEB-INF\shielded-container-lib
2. download liferay-portal-database-all-in-one-support and put it in TOMCAT_HOME\webapps\ROOT\WEB-INF\lib
3. in your -service module's bnd.bnd after "-dsannotations-options: inherit" add follows:
Especially the point 3, there is no document mentioned so far (maybe I have not studied deeply enough)
Super thank to Mr. Antonio Musarra. He selflessly shared code and suggestions, which helped me a lot.