What is entity and its precautions when designing in JPA?

Entity

The Entity class is a class that is mapped 1:1 with tables in the actual database. It should only have columns that exist in the DB as attributes.

How are entities mapped?

@JoinColumn(name = “name_of_FK_joining_2_tables”)
//Name is “team_id” or name of FK

If you omit this attribute, JPA finds FK via Field name (team) + _ + table column name reference like

(TEAM_ID) = team_TEAM_ID

Precautions

Never use setters indiscriminately

When creating entities, indiscriminate use of setters can change the value of an object (Entity), so object consistency cannot be guaranteed. To elaborate, when entity is managed by PersistenceContext and its value is changed, its updated value is updated into DB. But if setter is open to be used, it opens up random accidental changes of its value, making it hard for 유지보수. This applies not only to entity, but DTO as well.

All 연관관계 in LAZY

I explained this in my fetchType post

Reset collections at field level immediately

Tbc