To have the server logs and messages printed to System.out on your command prompt screen, you can start the server in verbose mode. This makes it easy to do simple debugging using print statements, without having to view the server.log file every time.
To start the server in verbose mode, use the --verbose option as follows:
asadmin start-domain --user adminuser --verbose [domain-name]
On Windows platforms, you must perform an extra preparation step if you want to use Ctrl-Break to print a thread dump. In the as-install/asenv.bat file, change AS_NATIVE_LAUNCHER="false" to AS_NATIVE_LAUNCHER="true".
When the server is in verbose mode, messages are logged to the console or terminal window in addition to the log file. In addition, pressing Ctrl-C stops the server and pressing Ctrl-\ (on UNIX platforms) or Ctrl-Break (on Windows platforms) prints a thread dump. On UNIX platforms, you can also print a thread dump using the jstack command (see http://java.sun.com/javase/6/docs/technotes/tools/share/jstack.html) or the command kill -QUIT process_id.