CODEWITHSUNDEEP
javahibernatejpahibernate-mappingmany-to-one
Narges
Narges

Reputation: 1355

Can a @ManyToOne JPA relation be null?

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?

Upvotes: 33

Views: 67192

Answers (3)

Vlad Mihalcea
Vlad Mihalcea

Reputation: 153690

The @ManyToOne associations are optional by default, so you don't need to set anything if you want them to be nullable.

However, because you set the optional=false attribute, you made it mandatory.

So instead of:

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

Set it like this:

@ManyToOne(fetch = FetchType.LAZY)

The optional is true by default.

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

Upvotes: 78

Oleksandr_DJ
Oleksandr_DJ

Reputation: 1515

Only this helped me:

public class TopUp {
    @ManyToOne
    @JoinColumn(columnDefinition="integer", name="subtype_id")
    private SubType subType;
}

columnDefinition is a solution!

Upvotes: 0

Sarwar kamal
Sarwar kamal

Reputation: 111

try this:

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

Upvotes: 5

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