Hibernate Hello World Example in Eclipse (Annotation)

October 23, 2016 by javainterviewpoint Leave a Comment

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In the previous article, we wrote our first Hibernate Hello World Example using XML Mapping, configuring hibernate through XML configuration is a bit complex process this can be done easily if we are using Annotation. In this Hibernate Hello World Example, we will learn how to write a simple Hibernate application using JPA Annotations.

Creating table

Create an EMPLOYEE Table, simply Copy and Paste the following SQL query in the query editor to get the table created.

CREATE TABLE "EMPLOYEE" 
   (	"ID" NUMBER(10,0) NOT NULL ENABLE, 
	"NAME" VARCHAR2(255 CHAR), 
	"AGE" NUMBER(10,0), 
	"DEPT" VARCHAR2(255 CHAR), 
	 PRIMARY KEY ("ID")
	 );

Folder Structure:

Create a simple Maven Project “HibernateTutorial” and create a package for our source files “com.javainterviewpoint” under src/main/java

Now add the following dependency in the POM.xml

 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0%20http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>
   <groupId>HibernateTutorial</groupId>
   <artifactId>HibernateTutorial</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <properties>
      <hibernate.version>4.3.11.Final</hibernate.version>
      <oracle.connector.version>11.2.0</oracle.connector.version>
   </properties>

   <dependencies>
     <!-- Hibernate -->
     <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>${hibernate.version}</version>
     </dependency>

     <!-- Oracle -->
     <dependency>
        <groupId>com.oracle</groupId>
        <artifactId>ojdbc14</artifactId>
        <version>${oracle.connector.version}</version>
     </dependency>
   </dependencies>
   <build>
     <sourceDirectory>src</sourceDirectory>
     <plugins>
       <plugin>
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.3</version>
         <configuration>
         <source>1.7</source>
         <target>1.7</target>
         </configuration>
       </plugin>
     </plugins>
   </build>
 </project>

Create the Java classes Employee.java and EmployeeHibernateExample.java under com.javainterviewpoint folder.
Place the hibernate.cfg.xml under the src/main/resources directory

Hibernate Hello World Example in Eclipse

Employee.java

Create a new Java file Employee.java under the package com.javainterviewpoint and add the following code

package com.javainterviewpoint;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="EMPLOYEE")
public class Employee implements Serializable 
{
    private static final long serialVersionUID = -889976693182180703L;
    
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    
    @Column(name="NAME")
    private String name;
    
    @Column(name="AGE")
    private int age;
    
    @Column(name="DEPT")
    private String dept;
    
    public Employee()
    {
        super();
    }

    public Employee(int id, String name, int age, String dept)
    {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.dept = dept;
    }
    
    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;
    }
    public int getAge()
    {
        return age;
    }
    public void setAge(int age)
    {
        this.age = age;
    }
    public String getDept()
    {
        return dept;
    }
    public void setDept(String dept)
    {
        this.dept = dept;
    }
    @Override
    public String toString()
    {
        return "Employee [id=" + id + ", name=" + name + ", age=" + age + ", dept=" + dept + "]";
    }
    @Override
    public int hashCode()
    {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((dept == null) ? 0 : dept.hashCode());
        result = prime * result + id;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj)
    {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Employee other = (Employee) obj;
        if (age != other.age)
            return false;
        if (dept == null)
        {
            if (other.dept != null)
                return false;
        } else if (!dept.equals(other.dept))
            return false;
        if (id != other.id)
            return false;
        if (name == null)
        {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
}

Our Employee class is a simple POJO class consisting of the getters and setters for the Employee class properties (id, name, age, dept).

In the POJO class, we have used the below JPA Annotations.

@Entity – This annotation will mark our Employee class as an Entity Bean.
@Table – @Table annotation will map our class to the corresponding database table. You can also specify other attributes such as indexes, catalog, schema, uniqueConstraints. The @Table annotation is an optional annotation if this annotation is not provided then the class name will be used as the table name.
@Id – The @Id annotation marks the particular field as the primary key of the Entity. We have specified the strategy as “AUTO” so that hibernate choose the optimal strategy for the database. Say for example SEQUENCE Strategy is supported by Oracle and not MySql and IDENTITY strategy is supported by MySQL but not Oracle. So it is better to leave it as AUTO.
@Column – This annotation maps the corresponding fields to their respective columns in the database table.

hibernate.cfg.xml

Place the hibernate.cfg.xml file also under the src/main/resources folder

 <?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
 "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

 <session-factory>

 <!-- Database connection settings -->
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>
<property name="hibernate.connection.url">jdbc:oracle:thin:@mydb:40051:dev</property>
<!-- JDBC connection pool (use the built-in) --> 
<property name="connection.pool_size">1</property> 

<!-- SQL dialect --> 
<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property> 

<!-- Echo all executed SQL to stdout --> 
<property name="show_sql">true</property> 

<!-- Drop and re-create the database schema on startup --> 
<property name="hibernate.hbm2ddl.auto">update</property> 

<!-- Entity class -->
 <mapping class="com.javainterviewpoint.Employee" />
</session-factory> 

</hibernate-configuration>

First and foremost property is for specifying the JDBC Driver class, in my case it OracleDriver

<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

Give the connection URL for connecting the database and provide username and password for connecting the above database

 <property name="hibernate.connection.url">jdbc:oracle:thin:@mydb:40051:dev</property>
 <property name="hibernate.connection.username">root</property>
 <property name="hibernate.connection.password">root</property>

Specify the connection pool size, this property limits the number of connections in the Hibernate connection pool.

<property name="connection.pool_size">1</property>

Dialect Property makes the Hibernate generate the SQL for the corresponding database which is being used. In this example we are using Oracle database hence Oracle query will be generated. If you are using MySQL database then you need to change the dialect accordingly.

<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>

The show_sql property will print the executed sql in the console when set to true.

<property name="show_sql">true</property>

If the property “hibernate.hbm2ddl.auto” is set to “create” This will drop and recreate the database schema on every execution. If it is set to “update” then the database schema will be updated every time rather than dropping and recreating.

<property name="hibernate.hbm2ddl.auto">update</property>

Under the Mapping tag class property give our Entity class name

<mapping class="com.javainterviewpoint.Employee" />

EmployeeHibernateExample.java

package com.javainterviewpoint;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class EmployeeHibernateExample
{
    public static void main(String args[])
    {
        //Reading the hibernate configuration file
        Configuration configuration = new Configuration().configure("hibernate.cfg.xml");
        StandardServiceRegistryBuilder srb = new StandardServiceRegistryBuilder();
        srb.applySettings(configuration.getProperties());
        ServiceRegistry serviceRegistry = srb.build();
        
        //Create SessionFacctory
        SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        
        //Create Session from SessionFactory
        Session session = sessionFactory.openSession();
        
        //Begin the transaction
        session.beginTransaction();
        
        //Create Employee object
        Employee ee = new Employee();
        
        //Set value to it properties
        ee.setAge(100);
        ee.setDept("IT");
        ee.setName("JIP");
        
        //Persist the employee object
        session.save(ee);
        
        //Commit the changes
        session.getTransaction().commit();
        //Close the session
        session.close();
    }
}

Create the Configuration object and read the configuration file using the configure() method.

Configuration configuration = new Configuration().configure("hibernate.cfg.xml");

Get the SessionFactory object through the buildSessionFactory() method of the configuration object.

SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);

openSession() method opens up the new session and begin a new transaction

Session session = sessionFactory.openSession();
session.beginTransaction();

Create a new Employee object and set values to its properties, we have set value for the property id, oracle will create a sequence and will insert value for it.

Employee ee = new Employee();
ee.setAge(100);
ee.setDept("IT");
ee.setName("JIP");

save() method of the session object will persist the employee object into the database.

session.save(ee);

Finally get the transaction and commit the changes and close the session.

session.getTransaction().commit();
session.close();

Console:

Oct 20, 2016 5:25:56 PM org.hibernate.tool.hbm2ddl.TableMetadata <init>
INFO: HHH000037: Columns: [id, age, name, dept]
Oct 20, 2016 5:25:56 PM org.hibernate.tool.hbm2ddl.TableMetadata <init>
INFO: HHH000108: Foreign keys: []
Oct 20, 2016 5:25:56 PM org.hibernate.tool.hbm2ddl.TableMetadata <init>
INFO: HHH000126: Indexes: [sys_c0014161]
Oct 20, 2016 5:25:56 PM org.hibernate.tool.hbm2ddl.SchemaUpdate execute
INFO: HHH000232: Schema update complete
Hibernate: select hibernate_sequence.nextval from dual
Hibernate: insert into EMPLOYEE (AGE, DEPT, NAME, id) values (?, ?, ?, ?)

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