Problem in <one-to-one> relation mapping

[Sai Kiran nukala]

Hi frnds...i got a prob. i am posting everything what i wrote....In database there are two tables Person and Car

Person table(id,name,address)
Car table(id,brand,person_id)....person_id is FK from person table.

Person Class:

   

package com.examples;

public class Person {
private int id;
private String name;
private String address;
private Car car;

public Car getCar() {
	return car;
}
public void setCar(Car car) {
	this.car = car;
}
public String getAddress() {
	return address;
}
public void setAddress(String address) {
	this.address = address;
}
public int getId() {
	return id;
}
public void setId(int id) {
	this.id = id;
}
public String getName() {
	return name;
}
public void setName(String name) {
	this.name = name;
}

}

 

Car Class:

   
package com.examples;

public class Car {

	private int id;
	private String brand;

	
	public String getBrand() {
		return brand;
	}
	public void setBrand(String brand) {
		this.brand = brand;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}

}


 

Car Mapping file:

   

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.examples.Car" table="car">
 
 <id name="id" column="id">
 <generator class="native"></generator> 
 </id>
 
 <property name="brand" column="brand" type="string"/>

</class>

</hibernate-mapping>

 

Person Mapping file:

   

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.examples.Person" table="person">
 
 <id name="id" column="id">
 <generator class="native"></generator> 
 </id>
 
 <property name="name" column="name" type="string"/>
 <property name="address" column="address" type="string"/>
 
 <many-to-one name="car" column="person_id" class="com.examples.Car" unique="true" cascade="save-update,delete">
 </many-to-one>

</class>

</hibernate-mapping>
 

Connection class where i created session and all others.

   
package com.examples;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class Connection {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		Configuration config = new Configuration().configure();
		
		SessionFactory sessionFactory = config.buildSessionFactory();
		Session session = sessionFactory.openSession();
		session.beginTransaction();
		Person person = new Person();
		person.setAddress("Hyd");
		person.setName("saikiran");
		Car car = new Car();
		car.setBrand("GE");
		person.setCar(car);
		session.saveOrUpdate(person);
		session.flush();
		session.beginTransaction().commit();
		sessionFactory.close();
		System.out.println("inserting..");
		
	}

}



 

here i created one-to-one mapping using <many-to-one> relation by putting "unique" attribute to true in Person mapping file. And when i execute it i got an error which is shown below:

   

Hibernate: insert into car (brand) values (?)
Oct 5, 2009 1:26:36 AM org.hibernate.util.JDBCExceptionReporter logExceptions
WARNING: SQL Error: 1364, SQLState: HY000
Oct 5, 2009 1:26:36 AM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: Field 'person_id' doesn't have a default value
Exception in thread "main" org.hibernate.exception.GenericJDBCException: could not insert: [com.examples.Car]
	at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:126)
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:114)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
	at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:64)
	at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2176)
	at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2656)
	at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:71)
	at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)
	at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:321)
	at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:204)
	at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:130)
	at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:210)
	at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:195)
	at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:117)
	at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
	at org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:535)
	at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:527)
	at org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:523)
	at com.examples.Connection.main(Connection.java:25)
Caused by: java.sql.SQLException: Field 'person_id' doesn't have a default value
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055)
	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3558)
	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3490)
	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109)
	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2648)
	at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2362)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2280)
	at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2265)
	at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:94)
	at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:57)
	... 15 more

 

Frnds please help me in clearing this mapping relation i'm very confused with this. Waiting for your valuable replies. If i did any mistake in the above code. Please correct me...

Thank in advance.

[Ben Narendren]

Since the CAR table has the PERSON_ID column (I find this a little unusual though), I am assuming the Car object is pointing to a Person object. In that case your Car class should be

package com.examples;

public class Car {

	private int id;
	private String brand;
        private Person person
	
	public String getBrand() {
		return brand;
	}
	public void setBrand(String brand) {
		this.brand = brand;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
        
        // Person getter and setter

}

and your car mapping should be

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.examples.Car" table="car">
 
 <id name="id" column="id">
 <generator class="native"></generator> 
 </id>
 
 <property name="brand" column="brand" type="string"/>

  <many-to-one name="person" column="person_id" class="com.examples.Person" unique="true" cascade="save-update,delete">  
  </many-to-one> 

</class>

</hibernate-mapping>

If you truly really want a bidirectional relationship and wish a pointer from person to car, the person mapping should be

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.examples.Person" table="person">
 
 <id name="id" column="id">
 <generator class="native"></generator> 
 </id>
 
 <property name="name" column="name" type="string"/>
 <property name="address" column="address" type="string"/>
 
 <one-to-one name="car"
  class="com.examples.Car"
  property-ref="person"/>

</class>

</hibernate-mapping>