Hibernate Framework Architecture and Basics
Hibernate Hello World Tutorial
Hibernate XML Configuration Example
Hibernate Java Configuration Example
Hibernate Transaction Management
Hibernate/JPA - Primary Key Generation Strategies
JPA and Hibernate Cascade Types
Hibernate - Save an Entity Example
Hibernate - Persist an Entity Example
Hibernate - saveOrUpdate() Method Example
Hibernate - get(), load() and byId() Method
Hibernate - merge() Example
Hibernate - Delete or Remove an Entity Example
Hibernate - load() Method Example
Hibernate Session.clear() Method Example
Hibernate One to One Mapping
Hibernate One to Many Mapping
Hibernate Many to Many Annotation
Hibernate One to Many CRUD Example
Hibernate One to One CRUD Example
Hibernate Inheritance Mapping
Hibernate Query Language
Hibernate CRUD Operations Example
Hibernate Session Interface Methods
JSP Servlet Hibernate CRUD Example
Hibernate Registration Form Example
Login Form using JSP + Servlet + Hibernate + MySQL
More .........
In Hibernate, an entity can be removed from a database by calling the Session.delete() or Session.remove(). Using these methods, we can remove a transient or persistent object from datastore.
The following snappits or examples demonstrate the use of Session.delete() and Session.remove() methods.
Session.delete(Object object) Method
Remove a persistent instance from the datastore. The argument may be an instance associated with the receiving Session or a transient instance with an identifier associated with existing persistent state. This operation cascades to associated instances if the association is mapped with cascade="delete".
EntityManager.remove(Object entity)
Remove the entity instance.
In this article, we will JPA annotations for mapping between the Student Java class and database table.
Technologies and tools used
- Hibernate 5.3.7.Final
- IDE - Eclipse Noen
- Maven 3.5.3
- JavaSE 1.8
- MySQL - 8.0.13
Let's start developing step by step Hibernate application using Maven as project management and build tool.
Development Steps
- Create a Simple Maven Project
- Project Directory Structure
- Add jar Dependencies to pom.xml
- Creating the JPA Entity Class(Persistent class)
- Create a Hibernate configuration file - Java Configuration
- Removing an entity using delete() method
- Removing an entity using remove() method
- Create the Main class and Run an Application
1. Create a Simple Maven Project
Use the How to Create a Simple Maven Project in Eclipse article to create a simple Maven project in Eclipse IDE.
2. Project Directory Structure
The project directory structure for your reference -
3. Add jar Dependencies to 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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>net.javaguides.hibernate</groupId>
<artifactId>hibernate-tutorial</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>hibernate-remove-entity-example</artifactId>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.3.7.Final</version>
</dependency>
</dependencies>
<build>
<sourceDirectory>src/main/java</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
4. Creating the JPA Entity Class(Persistent class)
Let's create a Student persistent class that is mapped to a database table.

A simple Persistent class should follow some rules:
- A no-arg constructor: It is recommended that you have a default constructor at least package visibility so that hibernate can create the instance of the Persistent class by newInstance() method.
- Provide an identifier property: It is better to assign an attribute as id. This attribute behaves as a primary key in a database.
- Declare getter and setter methods: The Hibernate recognizes the method by getter and setter method names by default.
- Prefer non-final class: Hibernate uses the concept of proxies, that depend on the persistent class. The application programmer will not be able to use proxies for lazy association fetching.
Create a Student entity class under net.javaguides.hibernate.entity package as follows.
package net.javaguides.hibernate.entity;
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 = "student")
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;
@Column(name = "first_name")
private String firstName;
@Column(name = "last_name")
private String lastName;
@Column(name = "email")
private String email;
public Student() {
}
public Student(String firstName, String lastName, String email) {
this.firstName = firstName;
this.lastName = lastName;
this.email = email;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
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 getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "Student [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", email=" + email + "]";
}
}
5. Create a Hibernate configuration file - Java Configuration
The HibernateUtil Java configuration file contains information about the database and mapping file.
HibernateUtil is a helper class to bootstrap hibernate SessionFactory.Add the Student entity to MetadataSources for mapping.
package net.javaguides.hibernate.util;
import java.util.Properties;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.cfg.Environment;
import org.hibernate.service.ServiceRegistry;
import net.javaguides.hibernate.entity.Student;
public class HibernateUtil {
private static SessionFactory sessionFactory;
public static SessionFactory getSessionFactory() {
if (sessionFactory == null) {
try {
Configuration configuration = new Configuration();
// Hibernate settings equivalent to hibernate.cfg.xml's properties
Properties settings = new Properties();
settings.put(Environment.DRIVER, "com.mysql.cj.jdbc.Driver");
settings.put(Environment.URL, "jdbc:mysql://localhost:3306/hibernate_db?useSSL=false");
settings.put(Environment.USER, "root");
settings.put(Environment.PASS, "root");
settings.put(Environment.DIALECT, "org.hibernate.dialect.MySQL5Dialect");
settings.put(Environment.SHOW_SQL, "true");
settings.put(Environment.CURRENT_SESSION_CONTEXT_CLASS, "thread");
settings.put(Environment.HBM2DDL_AUTO, "create-drop");
configuration.setProperties(settings);
configuration.addAnnotatedClass(Student.class);
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
.applySettings(configuration.getProperties()).build();
sessionFactory = configuration.buildSessionFactory(serviceRegistry);
} catch (Exception e) {
e.printStackTrace();
}
}
return sessionFactory;
}
}
6. Removing an entity using the delete() method
The following example deletes transient and persistent objects from the datastore using the Session.delete() method.
package net.javaguides.hibernate.dao;
import org.hibernate.Session;
import org.hibernate.Transaction;
import net.javaguides.hibernate.entity.Student;
import net.javaguides.hibernate.util.HibernateUtil;
public class SessionDeleteExample {
public void deleteStudent(int id) {
Transaction transaction = null;
try (Session session = HibernateUtil.getSessionFactory().openSession()) {
// start a transaction
transaction = session.beginTransaction();
// Delete a persistent object
Student student = session.get(Student.class, id);
if (student != null) {
session.delete(student);
System.out.println("student 1 is deleted");
}
// Delete a transient object
Student student2 = new Student();
student2.setId(2);
session.delete(student2);
System.out.println("Student 2 is deleted");
// commit transaction
transaction.commit();
} catch (Exception e) {
if (transaction != null) {
transaction.rollback();
}
e.printStackTrace();
}
}
}
7. Removing an entity using the remove() method
The following example deletes transient and persistent objects from the datastore using Session.remove() method.
package net.javaguides.hibernate.dao;
import org.hibernate.Session;
import org.hibernate.Transaction;
import net.javaguides.hibernate.entity.Student;
import net.javaguides.hibernate.util.HibernateUtil;
public class SessionRemoveExample {
public void removeStudent(int id) {
Transaction transaction = null;
try (Session session = HibernateUtil.getSessionFactory().openSession()) {
// start a transaction
transaction = session.beginTransaction();
// Delete a persistent object
Student student = session.get(Student.class, id);
if (student != null) {
session.remove(student);
System.out.println("student 1 is deleted");
}
// Delete a transient object
Student student2 = new Student();
student2.setId(2);
session.remove(student2);
System.out.println("Student 2 is deleted");
// commit transaction
transaction.commit();
} catch (Exception e) {
if (transaction != null) {
transaction.rollback();
}
e.printStackTrace();
}
}
}
8. Create the main App class and Run an Application
Let's test Hibernate application to connect MySQL database.
package net.javaguides.hibernate;
import net.javaguides.hibernate.dao.SessionDeleteExample;
import net.javaguides.hibernate.dao.SessionRemoveExample;
import net.javaguides.hibernate.dao.SessionSaveExample;
import net.javaguides.hibernate.entity.Student;
public class App {
public static void main(String[] args) {
// first save few records to database
SessionSaveExample studentDao = new SessionSaveExample();
Student s1 = new Student("Ramesh", "Fadatare", "rameshfadatare@javaguides.com");
Student s2 = new Student("John", "Cena", "johncena@javaguides.com");
studentDao.saveStudent(s1);
studentDao.saveStudent(s2);
// delete student
SessionDeleteExample deleteExample = new SessionDeleteExample();
deleteExample.deleteStudent(1);
// delete second student
SessionRemoveExample persistExample = new SessionRemoveExample();
persistExample.removeStudent(2);
}
}
Output
GitHub Repository
The complete source code of this article is available on my GitHub Repository - https://github.com/RameshMF/Hibernate-ORM-Tutorials
Conclusion
In this article, we have created a simple hibernate application to demonstrate the use of Session.delete() and Session.remove() methods.
You can learn more about Hibernate ORM Framework at Hibernate Tutorial
References
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