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.

Answer 2

try this:

@JoinColumn(name = "subType_id", nullable = true)