Hibernate: Bidirectional toString causes a StackOverflowError

Parent prints child, child prints parent. Lombok's @Data generates exactly this by default.

Code

@Entity
@Data                      // includes toString of ALL fields
class Order {
    @OneToMany(mappedBy = "order") List<OrderItem> items;
}

@Entity
@Data
class OrderItem {
    @ManyToOne Order order;    // back to the start
}

Output

java.lang.StackOverflowError
  at Order.toString -> OrderItem.toString -> Order.toString ...

Fix: @ToString(exclude = "order") or write toString by hand.

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Published 2026-08-11