I am using Hibernate 3.2.6 with the entities configured using annotations. DB is PostgreSQL.

I want to persist an object which has a collection associated with it. The collection should also be persisted when the parent object is persisted.

Say the parent object is foo and the collection objects are bar, the table structure is as below

Foo table:

CREATE SEQUENCE foo_id_seq;

CREATE TABLE foo
(
id integer primary key default nextval('foo_id_seq'),
<other fields>
)

Bar table:

CREATE SEQUENCE bar_id_seq;

CREATE TABLE bar
(
id integer primary key default nextval('bar_seq'),
foo_id integer,
<other fields>,
CONSTRAINT bar_has_foo_id FOREIGN KEY (foo_id)
REFERENCES foo (id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION
)

The entity mapping:

Foo:

@Entity(name = "foo")
public class Foo {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int id;
@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "foo_id")
@OrderBy("id")
private List<Bar> barList;
<getters and setters>
}

Bar:

@Entity(name = "bar")
public class Bar {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
@ManyToOne(targetEntity = Foo.class)
@JoinColumn(name = "foo_id")
private Foo foo;
<getters and setters>
}

Now when I try to store a Foo object with associated Bar objects I want the Foo as well as Bar objects to be saved. The code for this would be as below:

Foo foo = new Foo();
Bar bar0 = new Bar();
Bar bar1 = new Bar();
List<Bar> barList = new ArrayList<Bar>();
barList.add(bar0);
barList.add(bar1);
foo.setBarList(barList);
<persist foo>

This works fine. Both my Foo as well as Bar objects get saved.

Now if I add a constraint to the Bar table that foo_id foreign key is not null i.e
foo_id integer not null, then the above code ceases to work and I get an exception saying

2140 [main] ERROR org.hibernate.util.JDBCExceptionReporter - ERROR: null value in column "foo_id" violates not-null constraint

org.springframework.dao.DataIntegrityViolationException: could not insert: [Bar]; nested exception is org.hibernate.exception.ConstraintViolationException: could not insert: [Bar]


I can guess as to what is happening. When I try to store a foo object with associated bar objects then the bar table is populated first with foo_id as null. Then the foo table is populated. Now the foo_id column of bar table is updated with the stored foo id. But when I add a not null constraint the above sequence of events causes a DB error.

My question is how do I maintain my not null constraint and also save the foo object and it's associated bar object collection in one go?

You didn't provide Foo.setBarList() implementation but I believe that you just have a one like



I.e. 'Bar.foo' property is uninitialized.

The proper way to implement the method is below:


Also you should specify one end of your bidirectional association as inverse and add not-null constraint. I.e. the mappings look as follows: