Spring used your constructor (having P and 1).
Then it set the properties (overwriting with Q and 2).
You can debug by putting System.out.println inside the constructor method, showing that the program passed that area.
The first 2 steps in a bean cycle are (from Spring In Action 3rd Edition):
1. Spring instantiates the bean.
2. Spring injects values and bean references into the bean’s properties.
3. <etc....>
-k
[
SpringSource Certified Spring Professional - Practice Tests]