Component Class:
A class is said to be a component class if it is completely depends upon its container class life cycle and it is stored as a member variable not as an instance.
Component mapping:
If an entity class has a reference entity as a component variable then this property can mapped by using <component> element.
Example:
Student.java
/**
* This class represents a persistent class for Student.
* @author javawithease
*/
public class Student {
//data members
private int studentId;
private String firstName;
private String lastName;
private String rollNo;
private int age;
private StudentClass studentClass;
//no-argument constructor
public Student(){
}
//argument constructor
public Student(String firstName, String lastName, String
rollNo, int age, StudentClass studentClass){
this.firstName = firstName;
this.lastName = lastName;
this.rollNo = rollNo;
this.age = age;
this.studentClass = studentClass;
}
//getter and setter methods
public int getStudentId() {
return studentId;
}
public void setStudentId(int studentId) {
this.studentId = studentId;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getRollNo() {
return rollNo;
}
public void setRollNo(String rollNo) {
this.rollNo = rollNo;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public StudentClass getStudentClass() {
return studentClass;
}
public void setStudentClass(StudentClass studentClass) {
this.studentClass = studentClass;
}
} |
StudentClass.java
/**
* This class represents a persistent class for Subject.
* @author javawithease
*/
public class StudentClass {
//data members
private String classId;
private String className;
//no argument constructor
public StudentClass(){
}
//argument constructor
public StudentClass(String className){
this.className = className;
}
//getter and setter methods
public String getClassId() {
return classId;
}
public void setClassId(String classId) {
this.classId = classId;
}
public String getClassName() {
return className;
}
public void setClassName(String className) {
this.className = className;
}
} |
hibernate.cfg.xml
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration SYSTEM
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="dialect">
org.hibernate.dialect.OracleDialect
</property>
<property name="connection.url">
jdbc:oracle:thin:@localhost:1521:XE
</property>
<property name="connection.username">
system
</property>
<property name="connection.password">
oracle
</property>
<property name="connection.driver_class">
oracle.jdbc.driver.OracleDriver
</property>
<property name="hbm2ddl.auto">
update
</property>
<property name="show_sql">
true
</property>
<mapping resource="student.hbm.xml"/>
</session-factory>
</hibernate-configuration> |
student.hbm.xml
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-mapping SYSTEM
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.javawithease.business.Student" table="Student">
<id name="studentId" type="int" column="Student_Id">
<generator class="native"></generator>
</id>
<property name="firstName" column="First_Name" type="string"/>
<property name="lastName" column="Last_Name" type="string"/>
<property name="rollNo" column="RollNo" type="string"/>
<property name="age" column="Age" type="int"/>
<component name="studentClass"
class="com.javawithease.business.StudentClass">
<property name="classId" column="Class_Id" type="string"/>
<property name="className" column="Class_Name" type="string"/>
</component>
</class>
</hibernate-mapping> |
HibernateUtil.java
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
/**
* This is a utility class for getting the hibernate session object.
* @author javawithease
*/
public class HibernateUtil {
private static final SessionFactory sessionFactory =
buildSessionFactory();
private static SessionFactory buildSessionFactory() {
SessionFactory sessionFactory = null;
try {
//Create the configuration object.
Configuration configuration = new Configuration();
//Initialize the configuration object
//with the configuration file data
configuration.configure("hibernate.cfg.xml");
// Get the SessionFactory object from configuration.
sessionFactory = configuration.buildSessionFactory();
}
catch (Exception e) {
e.printStackTrace();
}
return sessionFactory;
}
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
} |
HibernateTest.java
import com.javawithease.persistence.StudentDBOperations;
/**
* This class is used for the hibernate operations.
* @author javawithease
*/
public class HibernateTest {
public static void main(String args[]){
StudentClass studentClass =
new StudentClass("IT1","MCA1");
//Create the student object.
Student student = new Student("Amani", "kaur",
"MCA/07/14", 27, studentClass);
StudentDBOperations obj = new StudentDBOperations();
//insert student object.
obj.addStudent(student);
//show all student object.
obj.showAllStudentDetails();
}
} |
StudentDBOperations.java
import java.util.List;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.javawithease.business.Student;
import com.javawithease.business.StudentClass;
/**
* This class contains the methods to interact with database.
* @author javawithease
*/
public class StudentDBOperations {
/**
* This method is used to insert a new student record.
* @param student
* @return studentId
* @author javawithease
*/
public Integer addStudent(Student student){
Transaction tx = null;
Integer studentId = null;
//Get the session object.
Session session =
HibernateUtil.getSessionFactory().openSession();
try{
tx = session.beginTransaction();
studentId = (Integer) session.save(student);
tx.commit();
}catch (HibernateException e) {
if(tx!=null){
tx.rollback();
}
e.printStackTrace();
}finally {
session.close();
}
return studentId;
}
/**
* This method is used retrieve and show the records.
* @author javawithease
*/
public void showAllStudentDetails(){
Transaction tx = null;
//Get the session object.
Session session =
HibernateUtil.getSessionFactory().openSession();
try{
tx = session.beginTransaction();
List<Student> students =
session.createQuery("FROM Student").list();
for(Student student : students){
System.out.println("First Name: "
+ student.getFirstName());
System.out.println("Last Name: "
+ student.getLastName());
System.out.println("RollNo: "
+ student.getRollNo());
System.out.println("Age: "
+ student.getAge());
StudentClass studentClass =
student.getStudentClass();
System.out.println("Class Name:"
+ studentClass.getClassName());
System.out.println("Class Id:"
+ studentClass.getClassId());
}
tx.commit();
}catch (HibernateException e) {
if(tx!=null){
tx.rollback();
}
e.printStackTrace();
}finally {
session.close();
}
}
} |
Output:
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: insert into Student (First_Name, Last_Name, RollNo,
Age, Class_Id, Class_Name, Student_Id) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: select student0_.Student_Id as Student1_0_,
student0_.First_Name as First2_0_, student0_.Last_Name as
Last3_0_, student0_.RollNo as RollNo0_, student0_.Age as
Age0_, student0_.Class_Id as Class6_0_, student0_.Class_Name
as Class7_0_ from Student student0_
First Name: Amani
Last Name: kaur
RollNo: MCA/07/14
Age: 27
Class Name:MCA1
Class Id:IT1 |
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