Debugging

IntelliJ IDEA provides a very powerful but simple to use the debugger that we can use to develop our microservices. If we go back to our ExampleService class, we can click on the gutter in the same line that our getHello method is and we can create a breakpoint, this will be visualized as a red dot on the gutter. Alternatively, we can use the keybinding Ctrl + F8 in Windows, command + F8 on a Mac.

Now, we can go back to the application class, click on the Kotlin icon but choose to debug instead of run. If we request again the URL http://localhost:8080/user/Kotlin, the debugger should stop the application and show our breakpoint.

When the application is stopped, we can see in the middle-bottom side of the screen, the Debugger window:

In this window on the left-hand side, we can see a section named Frames that allows us to navigate through the stack trace to the point where we were stopped.

On the right-hand side, we can see the variables and their value in the current scope of the debugger. Right-clicking on this allows us to define watches that will monitor values using expressions, or inspect objects to see all attributes and methods for existing values.
On the top, near the tabs, we have a vertical bar that contains buttons to navigate through the execution of the debugger, for example, to step in and out of functions calls, or continue running to the current cursor.

We can invoke the debugger from Maven phases and goals, right-click on the Maven Projects Windows to a phase or goal and choose Debug.