I guess your "real" constuctor is invoked by your code within your Flink
program. The default constructor is used during serialization between
operators. If you are interested in the internals, you can have a look
at the PojoSerializer . The POJO is created with the default
constrcutor and then filled. If you want to reduce the calls of
constructors you can also enable the object reuse mode  but this
requires your code to be correct to prevent side effects.
Am 09.03.18 um 21:24 schrieb NEKRASSOV, ALEXEI:
I added a default constructor to the class that represents messages
flowing through my Flink job graph – to satisfy Flink POJO requirements.
Although I don’t call that default constructor explicitly, the logs
show that it is called anyway.
Why is this happening?
In my test, for 77 incoming messages I see 77 calls to my “real”
constructor, but also another 77 calls – to default constructor, that
essentially create objects with no value.
Is this expected, or I’m doing something wrong?