To view detailed log-messaging in JDeveloper’s “Embedded OC4J Server – Log” window, do the following in JDeveloper 10g:

1. In the Applications Navigator, right click on the Project and select Project Properties.
2. Select Run/Debug.
3. Select Default in the “Run Configurations” window, and click on the Edit button.
4. In the Launch Settings window,  add the following parameter to the string in the Java Options field:

-Djbo.debugoutput=console

5. Click on OK.
6. Rebuild the project and run again to see the OC4J runtime debug information in JDeveloper’s Server Log window.