Debugging tips

The tutorial The NetBeans E-commerce Tutorial - Managing Sessions has many debugging tips and examples.
View/manage a list of breakpoints
open the debugger's Breakpoints window (Window > Debugging > Breakpoints).
Examining Client-Server Communication with the HTTP Monitor
1. activate the HTTP Monitor for the server you are using. Choose Tools > Servers. In the left column of the Servers window, select the server you are using (GlassFish). Then, in the main column, select the Enable HTTP Monitor option.
2. If your server is already running, you need to restart it. However, since we plan to use the debugger, and running the debugger restarts the server to communicate on a different port, just click the Debug Project ( ) button in the IDE's main toolbar. The server restarts, a debug session begins and the application's welcome page opens in your browser. The HTTP Monitor displays in the bottom region of the IDE.

Java