Hi Naehee, Short answer would be for historic reasons and compatibility reasons. It was implemented that way back in the days and we don't want to change the default type extraction logic. Otherwise user jobs that rely on the default type extraction logic for state storing would end up with a state stored in an incompatible way with the updated serializer.
This is not a problem for Table/SQL programs as we control the state internally, and that's why we were able to change the requirements for POJOs in Table/SQL programs. [1] Best, Dawid [1] https://ci.apache.org/projects/flink/flink-docs-master/docs/dev/table/types/#user-defined-data-types On 08/07/2021 00:09, Naehee Kim wrote: > According to the Flink doc, > > Flink recognizes a data type as a POJO type (and allows “by-name” > field referencing) if the following conditions are fulfilled: > > * The class is public and standalone (no non-static inner class) > * The class has a public no-argument constructor > * All non-static, non-transient fields in the class (and all > superclasses) are either public (and non-final) or have a public > getter- and a setter- method that follows the Java beans naming > conventions for getters and setters. > > > PojoSerializer uses Java reflection to access an object's fields. One > of PojoSerializer's constructor calls setAccessible(true) for all fields. > for (int i = 0; i < numFields; i++) { > this.fields[i].setAccessible(true); > } > Then, to my knowledge, it can set a field regardless of the field's > access control(private, public,..). > > However, its another constructor, called by PojoSerializerSnapshot, > doesn't call setAccessible(true). Does anyone know the reason why > setAccessible(true) is not called here? And why fields should be > public or have a public gettter- and setter- method? > > Regards, > Naehee > >
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