Can a @ManyToOne JPA relation be null?

Question

I have a table that has foreign key of another table (many to one relationship) but i want it to be nullable.

Something like this:

public class SubType() {

    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    private String id;

}

public class TopUp {

    @Column(nullable = true)
    @ManyToOne(optional = false, fetch = FetchType.LAZY)
    private SubType subType;

}

But @Column(nullable = true) throws the NullPointerException and says subtype can not be null. Is there any way to get the ManyToOne accept null?

Answer 1

You need to set:

@ManyToOne(optional = true, fetch = FetchType.LAZY)

not optional=false.

The @Column(nullable=true) is to instruct the DDL generation tool to include a NULL SQL column type constraint.

For more on optional vs nullable, check out this StackOverflow answer.