Idiom: Happy Camper;
used as a noun

First Example:
Pete: Hey Chip, what’s
going on?  You seem to be incredibly unhappy.
Chip: Every time I almost get
my work done, someone interrupts me. I’m not a happy
camper.
Pete: No kidding, you’ve
been quite irritated for the last couple of days.  I guess that project was tough huh?

Second Example:
Jean: You’re certainly a
happy camper after your trip to Europe.
Matt: I had a chance to
visit so many sites and try so many good things to eat.  What’s not to be happy about?

Meaning: 
Tobe a “happy camper” means to be satisfied,
cheerful or pleased with something, someone, or the result of something.  In the first example, Pete noticed Chip’s
demeanor and noticed how unhappy he was with something.  Chip explains that he keeps getting interrupted. This idiom is commonly used with a negative to mean unhappy.
In the second
example, Matt expresses his positive experience in Europe and why he was so
happy.  He was a satisfied customer, or a
Happy Camper.


https://www.languagesystems.com/