Insert on Parent only on a one-to-many relation

deepak · **Joined:** Wed Jan 28, 2004 7:43 am **Posts:** 1

Hi,

Is there any way to insert a row in the parent table alone using hibernate.

My case is like this

A department table is related to an employee table in one-to many fashion. But while trying to insert a row in department, i am force to add a set of employees also.The ddl used to create the schema are as follows

create table department (dept_id varchar(15) primary key,
dept_name varchar(50),
dept_location varchar(50));

create table employee (emp_id number(10) primary key,
emp_name varchar(50),
dept_id varchar(15),
foreign key (dept_id) references department(dept_id));

I used middlegen to create the mapping files they are as follows

Department.hbl.xml-----------------------
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

<hibernate-mapping>


<class
name="com.roche.dal.Department"
table="DEPARTMENT"
>

<id
name="deptId"
type="java.lang.String"
column="DEPT_ID"
>
<generator class="assigned" />
</id>

<property
name="deptName"
type="java.lang.String"
column="DEPT_NAME"
length="50"
/>
<property
name="deptLocation"
type="java.lang.String"
column="DEPT_LOCATION"
length="50"
/>




<set
name="employees"
lazy="true"
inverse="false"
cascade="delete"
>
<key>
<column name="DEPT_ID" />
</key>
<one-to-many
class="com.roche.dal.Employee"

/>
</set>

</class>
</hibernate-mapping>

employee.hbm.xml--------------------------
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

<hibernate-mapping>


<class
name="com.roche.dal.Employee"
table="EMPLOYEE"
>

<id
name="empId"
type="java.lang.String"
column="EMP_ID"
>
<generator class="assigned" />
</id>

<property
name="empName"
type="java.lang.String"
column="EMP_NAME"
length="50"
/>




<many-to-one
name="department"
class="com.roche.dal.Department"
not-null="true"
>
<column name="DEPT_ID" />
</many-to-one>


<one-to-one
name="employeeSecurityData"
class="com.roche.dal.EmployeeSecurityData"
outer-join="auto"
/>

<set
name="documentReviewDatas"
lazy="true"
inverse="true"
>
<key>
<column name="EMP_ID" />
</key>
<one-to-many
class="com.roche.dal.DocumentReviewData"
/>
</set>

<set
name="documentDatas"
lazy="true"
table="DOCUMENT_REVIEW_DATA"
>
<key>
<column name="EMP_ID" />
</key>
<many-to-many
class="com.roche.dal.DocumentData"
>
<column name="DOC_ID" />
</many-to-many>
</set>

</class>
</hibernate-mapping>

and my generated Department class is

import java.io.Serializable;
import java.util.Set;
import org.apache.commons.lang.builder.EqualsBuilder;
import org.apache.commons.lang.builder.HashCodeBuilder;
import org.apache.commons.lang.builder.ToStringBuilder;

/** @author Hibernate CodeGenerator */
public class Department implements Serializable {

/** identifier field */
private String deptId;

/** nullable persistent field */
private String deptName;

/** nullable persistent field */
private String deptLocation;

/** persistent field */
private Set employees;

/** full constructor */
public Department(String deptId, String deptName, String deptLocation, Set employees) {
this.deptId = deptId;
this.deptName = deptName;
this.deptLocation = deptLocation;
this.employees = employees;
}

/** default constructor */
public Department() {
}

/** minimal constructor */
public Department(String deptId, Set employees) {
this.deptId = deptId;
this.employees = employees;
}

public String getDeptId() {
return this.deptId;
}

public void setDeptId(String deptId) {
this.deptId = deptId;
}

public String getDeptName() {
return this.deptName;
}

public void setDeptName(String deptName) {
this.deptName = deptName;
}

public String getDeptLocation() {
return this.deptLocation;
}

public void setDeptLocation(String deptLocation) {
this.deptLocation = deptLocation;
}

public Set getEmployees() {
return this.employees;
}

public void setEmployees(Set employees) {
this.employees = employees;
}

public String toString() {
return new ToStringBuilder(this)
.append("deptId", getDeptId())
.toString();
}

public boolean equals(Object other) {
if ( !(other instanceof Department) ) return false;
Department castOther = (Department) other;
return new EqualsBuilder()
.append(this.getDeptId(), castOther.getDeptId())
.isEquals();
}

public int hashCode() {
return new HashCodeBuilder()
.append(getDeptId())
.toHashCode();
}

}

Since I want to have other tables related to employee, I can add an employee when ever a department is added.

Is there any configuration setting or any parameter in the mapping file so that i can insert to the parent table alone?

Thanks in advance
Deepak

michael · **Posted:** Wed Feb 04, 2004 10:41 am

Well just save a department with an empty Employee Set ...

fraguio · **Posted:** Wed Feb 04, 2004 3:29 pm

quite the opposite, i'm trying insert a set of child entities 'Boletin' ( Bulletin ) as the same time as i insert a new parent entity 'Usuario' ( User ).

is this possible only save de parent entity ?

.....
session.save( usuario );
.....

i think ( and i could like ) it's possible reading deepak's post but at the moment i haven't it achieved :-(

mapping files and code
-----------------------------------------------------------------

############################ ### Usuario.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

<hibernate-mapping>


<class
name="com.cca.database.hibernate.Usuario"
table="usuario"
>

<id
name="codUsuario"
type="java.lang.Long"
column="codUsuario"
>
<generator class="identity" />
</id>

<property
name="nombre"
type="java.lang.String"
column="nombre"
not-null="true"
length="200"
/>

.... more properties ....



... more asociations .....


<set
name="boletines"
lazy="true"
inverse="true"
>
<key>
<column name="codUsuario" />
</key>
<one-to-many
class="com.cca.database.hibernate.Boletin"
/>
</set>
... more asociations .....

</class>
</hibernate-mapping>

############################ ### Boletin.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

<hibernate-mapping>


<class
name="com.cca.database.hibernate.Boletin"
table="boletin"
>

<id
name="codBoletin"
type="java.lang.Long"
column="codBoletin"
>
<generator class="identity" />
</id>

<property
name="fechaBoletin"
type="java.sql.Timestamp"
column="fechaBoletin"
not-null="true"
length="19"
/>

.... more properties ....



<many-to-one
name="usuario"
class="com.cca.database.hibernate.Usuario"
not-null="true"
>
<column name="codUsuario" />
</many-to-one>

</class>
</hibernate-mapping>

############################### ### Java Code

... ... ... ...

Set bulletins = new HashSet();

Boletin bulletin1 = new Boletin( new Date(), "bulletin 1" );
bulletins.add( bulletin1 );
Boletin bulletin2 = new Boletin( new Date(), "bulletin 2" );
bulletins.add( bulletin2 );
Boletin bulletin3 = new Boletin( new Date(), "bulletin 3" );
bulletins.add( bulletin3 );

Transaction tx = session.beginTransaction();

Usuario usuario = new Usuario( "new user", ... more params..., bulletins );
session.save( usuario ); // Why the bulletins are not saved ???
tx.commit();

... ... ... ...

############################ ### Output Console

Hibernate: insert into usuario (nombre, apellidos, dniCifPasaporte, edad, sexo, eMail, domicilio, poblacion, cp,

telefono1, telefono2, login, password, personaContacto, codPais, codProvincia, codSector, codPerfil) values (?, ?,

?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: SELECT LAST_INSERT_ID()

-----------------------------------------------------------------

What's wrong ???

if this behavior isn't possible i don't know why the parent entity take instances of chil entities
in the contructor

Thanks in advance and sorry for my english !!!

Eduardo.
A Coru

michael · **Posted:** Wed Feb 04, 2004 3:48 pm

Ah, you want something like cascade, i suppose. Take a look at http://www.hibernate.org/hib_docs/reference/html/parent-child.html#parent-child-cascades

fraguio · **Posted:** Thu Feb 05, 2004 12:38 pm

Thanks for your reply, gloeglm.

... and this has been one step beyond. I've modified 'Usuario.hbm.xml' adding to the set 'boletines' the attribute 'cascade=all' as follows:

############################ ### Usuario.hbm.xml

...............

<set
name="boletines"
lazy="true"
inverse="true"
cascade="all"
>
<key>
<column name="codUsuario" />
</key>
<one-to-many
class="com.cca.database.hibernate.Boletin"
/>
</set>
...............

I've modified my code as follows:

############################### ### Java Code
Transaction tx = session.beginTransaction();

Set bulletins = new HashSet();
Usuario user = new Usuario( "new user", ... more params..., bulletins );

Boletin bulletin1 = new Boletin( new Date(), "bulletin1", user );
bulletins.add( bulletin1 ); // i've tried too user.getBulletins().add( bulletin1 )

Boletin bulletin2 = new Boletin( new Date(), "bulletin2", user );
bulletins.add( bulletin2 ); // i've tried too user.getBulletins().add( bulletin2 )

Boletin bulletin3 = new Boletin( new Date(), "bulletin3", user );
bulletins.add( bulletin3 ); // i've tried too user.getBulletins().add( bulletin3 )

session.save( usuario );
tx.commit();

--------------------------------------------------------------------------------

... and now my entity 'User' is persisted but only the entity 'bulletin1' it's too. Why 'bulletin2' and 'bulletin3' are not inserted in the DB ??

in view of i've described above i've modified my code as follows( only to satisfy my cusiosity ):

############################### ### Java Code
Transaction tx = session.beginTransaction();

Set bulletins = new HashSet();
Usuario user = new Usuario( "new user", ... more params..., bulletins );

Boletin bulletin1 = new Boletin( new Date(), "bulletin1", user );
bulletins.add( bulletin1 ); // i've tried too user.getBulletins().add( bulletin1 )
session.saveOrUpdate( user );

Boletin bulletin2 = new Boletin( new Date(), "bulletin2", user );
bulletins.add( bulletin2 ); // i've tried too user.getBulletins().add( bulletin2 )
session.saveOrUpdate( user );

Boletin bulletin3 = new Boletin( new Date(), "bulletin3", user );
bulletins.add( bulletin3 ); // i've tried too user.getBulletins().add( bulletin3 )
session.saveOrUpdate( user );

tx.commit();

--------------------------------------------------------------------------------

... and surprisingly was inserted in the DB, of course, the entity 'user' and the child entities 'bulletin1' and 'bulletin2'. Where is 'bulletin3' ??

i can't understand this behavior !!!

Thanks in advance and sorry for my english !!!

Eduardo.
A Coru

michael · **Posted:** Thu Feb 05, 2004 5:00 pm

What SQL is generated? How does your equals/hashCode look like? Is this really exactly the code you execute?

fraguio · **Posted:** Fri Feb 06, 2004 8:26 am

Yes gloeglm, this is really exactly the code i execute !! Are you too surpised for the obtained result ??

For my first test ( see reference in my last post ) the output console was as fowolls:

############################ ### Output Console

Hibernate: insert into usuario (nombre, apellidos, dniCifPasaporte, edad, sexo, eMail, domicilio, poblacion, cp, telefono1, telefono2, login, password, personaContacto, codPais, codProvincia, codSector, codPerfil) values(?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: SELECT LAST_INSERT_ID()
Hibernate: insert into boletin (fechaBoletin, rutaPdf, codUsuario) values (?, ?, ?)
Hibernate: SELECT LAST_INSERT_ID()

For the second test the output console was as fowolls:

############################ ### Output Console

Hibernate: insert into usuario (nombre, apellidos, dniCifPasaporte, edad, sexo, eMail, domicilio, poblacion, cp, telefono1, telefono2, login, password, personaContacto, codPais, codProvincia, codSector, codPerfil) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: SELECT LAST_INSERT_ID()
Hibernate: insert into boletin (fechaBoletin, rutaPdf, codUsuario) values (?, ?, ?)
Hibernate: SELECT LAST_INSERT_ID()
Hibernate: insert into boletin (fechaBoletin, rutaPdf, codUsuario) values (?, ?, ?)
Hibernate: SELECT LAST_INSERT_ID()

Last, my equals and hashCode methods, generated by Hibernate CodeGenerator:

############################ ### Usuario.java

... ... ...

public boolean equals( Object other ) {
if( ! ( other instanceof Usuario ) ) {
return false;
}
Usuario castOther = ( Usuario )other;
return new EqualsBuilder()
.append( this.getCodUsuario(), castOther.getCodUsuario() )
.isEquals();
}

public int hashCode() {
return new HashCodeBuilder()
.append( getCodUsuario() )
.toHashCode();
}

... ... ...

############################ ### Boletin.java

... ... ...

public boolean equals( Object other ) {
if( ! ( other instanceof Boletin ) ) {
return false;
}
Boletin castOther = ( Boletin )other;
return new EqualsBuilder()
.append( this.getCodBoletin(), castOther.getCodBoletin() )
.isEquals();
}

public int hashCode() {
return new HashCodeBuilder()
.append( getCodBoletin() )
.toHashCode();
}

... ... ...

Curiously, in my second test, you can add the number of instances of 'Boletin' what you want, as follows:

############################### ### Java Code

... ... ...

Boletin bulletin1 = new Boletin( new Date(), "bulletin1", user );
user.getBulletins().add( bulletin1 ) // bulletin 1
session.saveOrUpdate( user );

... ... ...

Boletin bulletinN = new Boletin( new Date(), "bulletinN", user );
user.getBulletins().add( bulletinN ) // bulletin n
session.saveOrUpdate( user );

... ... ...

---------------------------------------------------------------------------

Only the first ans second instances of Boletin are inserted in the DB.

What's happen ??

Thanks.

Eduardo.

michael · **Posted:** Fri Feb 06, 2004 8:39 am

Most likely the problem is you insert a lot of elements into a hashSet which all have the same identifier (null) and all have the same hashCode and are all equal. What rather puzzles me is that you do saveOrUpdate() in between .. try calling session.flush() after every saveOrUpdate()

fraguio · **Posted:** Mon Feb 09, 2004 1:07 pm

all right gloeglm ...

if i call session.flush() after every saveOrUpdate(), the instances of bulletin are inserted in the database, but i would like, and i thought that hibernate worked in other manner.

Don't you think that if a parent entity take a Set of instances of child entities in the constructor, would be logical to persist the child entities in the same moment ( in the same sentence -> session.save( parent ) ) that the parent entity is persisted ?

i'm a new hibernate user and i'm trying to understand the tool's possibilities.

Thank you for your help.

Eduardo.

michael · **Posted:** Mon Feb 09, 2004 1:15 pm

You can not insert multiple new instances into a set, if your equals method relies on the identifier (they have all null as the id value). Every new entry will replace the old one.

emmanuel · **Posted:** Mon Feb 09, 2004 1:16 pm

It seems not to be related to Hibernate but to equals/hashcode Java specification. Try to implement a proper equals method http://www.hibernate.org/Documentation/EqualsAndHashCode

christian · **Posted:** Mon Feb 09, 2004 1:20 pm

The pattern described at this page is not a good practice! I added a comment...