I created a proxy service and added a Log action to log out the message body, but I didn't see the log on WebLogic console.
The problem is related with log level as the default level is higher than info level. Change the log level will solve it.
1. Enter the WSL admin console
2. Click on Environment->Servers
3. Click on Admin Server (or the appropriate server name of yours)
4. Select Logging tab
5. Click Advanced
6. Set Severity Level of Standard Out to Debug.
7. Click Save
After that, maybe a restart is needed.