Shambhuraje - Technology: May 2013

Here are steps to create sample hibernate application using eclipse. I am using hibernate version 4.2 and MySQL database for reference.

First I will create it using mapping xml file. Then convert same application to use annotation and finally JPA.

Create Java Project as:

Create java project - HibernateJPA

Create below packages in src folder by using option "create package"
com.test.beans

com.test.resources

com.test.dao

com.test.util

Add hibernate dependencies for project by right clicking on project "Build Path" --> Configure Build Path.

Under Libraries Tab: Add external jar button and add Hibernate required jar files.

antlr-2.7.7.jar
dom4j-1.6.1.jar
hibernate-commons-annotations-4.0.1.Final.jar
hibernate-core-4.2.0.Final.jar
hibernate-jpa-2.0-api-1.0.1.Final.jar
javassist-3.15.0-GA.jar
jboss-logging-3.1.0.GA.jar
jboss-transaction-api_1.1_spec-1.0.0.Final.jar

Also add mysql connector jar.

mysql-connector-java-3.1.14-bin.jar

Create HibernateUtil.java file under package com.test.util for creating and using SessionFactory object as:
For more details about building SessionFactory refer post Creating SessionFactory.
HibernateUtil.java

package com.test.util;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

public class HibernateUtil {

private static SessionFactory sessionFactory;

static{

try {

sessionFactory = new Configuration().configure("com/test/resources/hibernate.cfg.xml").buildSessionFactory();

}

catch (Exception e) {

throw new ExceptionInInitializerError(e);

}

public static SessionFactory getSessionFactory(){

return sessionFactory;

}

public static void shutDown(){

getSessionFactory().close();

}
}

Employee and Department classes which are persistace objects in package com.test.beans:

Employee.java

package com.test.beans;

public class Employee {

private Long empId;

private String firstName;
private String lastName;
private String designation;
private double salary;
private Department dept;
public Long getEmpId() {
        return empId;
}
public void setEmpId(Long empId) {
        this.empId = empId;
}
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 getDesignation() {
       return designation;
}
public void setDesignation(String designation) {
       this.designation = designation;
}
public double getSalary() {
      return salary;
}
public void setSalary(double salary) {
     this.salary = salary;
}
public Department getDept() {
     return dept;
}
public void setDept(Department dept) {
     this.dept = dept;
}
}

Department.java

package com.test.beans;

public class Department {
private long deptId;

private String deptName;
private String location;

public long getDeptId() {

return deptId;

}

public void setDeptId(long deptId) {

this.deptId = deptId;

}

public String getDeptName() {

return deptName;

}

public void setDeptName(String deptName) {

this.deptName = deptName;

}

public String getLocation() {

return location;

}

public void setLocation(String location) {

this.location = location;

}

We need hibernate configuration file for settings related to connecting database. (configuration file contains much more but for simple application, i am only defining minimum required settings)

hibernate.cfg.xml

<? xml version="1.0" encoding="UTF-8"?>

DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD/EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd" >

<hibernate-configuration>

<session-factory>

<property name="dialect">org.hibernate.dialect.MySQLDialect</property>

<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/test</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>
<property name="hibernate.current_session_context_class">thread</property>
<property name="hbm2ddl.auto">create</property>
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<property name="hibernate.use_sql_comments">true</property>
<mapping resource="com/test/beans/organization.hbm.xml" />
</session-factory>
</hibernate-configuration>

Now we need mapping file which defines mapping of Persistance classes with database tables:

organization.hbm.xml

< xml version="1.0"?>

DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

package="com.test.beans">

<class name="Department" table="DEPT">
     <id name="deptId" column="dept_id">
               <generator class="native" />
     </id>
     <property name="deptName" type="string" column="dept_name" unique="true"/>
     <property name="location" type="string" column="loc"/>
</class>
<class name="Employee" table="EMP" >
       <id name="empId" column="emp_id">
                 <generator class="native"></generator>
       </id>
       <property name="firstName" type="string" column="first_name" />
       <property name="lastName" type="string" column="last_name" />
       <property name="designation" type="string" column="degn" />
       <property name="salary" type="double" column="sal" />
       <many-to-one name="dept" column="dept" class="Department" />
</class>
</hibernate-mapping>

Hibernate application is ready and let's create test class to test the application.

Test.java

package com.test.dao;

import org.hibernate.Session;
import org.hibernate.Transaction;
import com.test.beans.Department;
import com.test.beans.Employee;
import com.test.util.HibernateUtil;

public class Test {

public static void main(String[] args) {

          Employee emp = new Employee();
          emp.setFirstName("fName");
          emp.setLastName("lName");
          emp.setDesignation("Java Developer");
          emp.setSalary(20000);
          Department dept= new Department();
          dept.setDeptName("Design");
          emp.setDept(dept);
          Session sess = HibernateUtil.getSessionFactory().openSession();
         Transaction tran = sess.beginTransaction();

sess.save(emp);

sess.flush();

tran.commit();
sess.close();

}

After running above class, Employee and Department data is stored in respective tables. You get console log to understand how hibernate works in background.

Console Log:

May 31, 2013 7:18:36 PM org.hibernate.annotations.common.Version

INFO: HCANN000001: Hibernate Commons Annotations {4.0.1.Final}

May 31, 2013 7:18:36 PM org.hibernate.Version logVersion

INFO: HHH000412: Hibernate Core {4.2.0.Final}

May 31, 2013 7:18:36 PM org.hibernate.cfg.Environment

INFO: HHH000206: hibernate.properties not found

May 31, 2013 7:18:36 PM org.hibernate.cfg.Environment buildBytecodeProvider

INFO: HHH000021: Bytecode provider name : javassist

May 31, 2013 7:18:36 PM org.hibernate.cfg.Configuration configure

INFO: HHH000043: Configuring from resource: com/test/resources/hibernate.cfg.xml

May 31, 2013 7:18:36 PM org.hibernate.cfg.Configuration getConfigurationInputStream

INFO: HHH000040: Configuration resource: com/test/resources/hibernate.cfg.xml

May 31, 2013 7:18:36 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity

WARN: HHH000223: Recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!

May 31, 2013 7:18:36 PM org.hibernate.cfg.Configuration addResource

INFO: HHH000221: Reading mappings from resource: com/test/beans/organization.hbm.xml

May 31, 2013 7:18:36 PM org.hibernate.internal.util.xml.DTDEntityResolver resolveEntity

WARN: HHH000223: Recognized obsolete hibernate namespace http://hibernate.sourceforge.net/. Use namespace http://www.hibernate.org/dtd/ instead. Refer to Hibernate 3.6 Migration Guide!

May 31, 2013 7:18:36 PM org.hibernate.cfg.Configuration doConfigure

INFO: HHH000041: Configured SessionFactory: null