Hibernate

How many types of association mapping are possible in hibernate?

There can be 4 types of association mapping in hibernate.

One to One
One to Many
Many to One
Many to Many

Define persistent classes?

Classes whose objects are stored in a database table are called as persistent classes.

What are the key components of Hibernate?

Key components of Hibernate are:

Configuration
Session
SessionFactory
Criteria
Query
Transaction

ORM is an acronym for Object-Relational mapping. It is a programming strategy to map object with the data stored in the database. It simplifies data creation, data manipulation, and data access. Object-Relational Mapping (ORM) is a technique that lets you query and manipulate data from a database using

Snippets

The configuration file contains information about the database and mapping file. Conventionally, its name should be hibernate.cfg.xml.
create an XML file named hibernate.cfg.xml under the resources folder

<!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>

        <!-- JDBC Database connection settings -->
        <property name="connection.driver_class">com.mysql.cj.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate_db?useSSL=false</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>

        <!-- JDBC connection pool settings ... using built-in test pool -->
        <property name="connection.pool_size">1</property>

        <!-- Select our SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

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

        <!-- Set the current session context -->
        <property name="current_session_context_class">thread</property>

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

        <!-- dbcp connection pool configuration -->
        <property name="hibernate.dbcp.initialSize">5</property>
        <property name="hibernate.dbcp.maxTotal">20</property>
        <property name="hibernate.dbcp.maxIdle">10</property>
        <property name="hibernate.dbcp.minIdle">5</property>
        <property name="hibernate.dbcp.maxWaitMillis">-1</property>
        <mapping class="net.javaguides.hibernate.entity.Student" />
    </session-factory>
</hibernate-configuration>

<!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>

<property name="connection.driver_class">com.mysql.cj.jdbc.Driver</property>

<property name="connection.url">jdbc:mysql://localhost:3306/hibernate_db?useSSL=false</property>

<property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>

<property name="current_session_context_class">thread</property>

<property name="hbm2ddl.auto">create-drop</property>

</session-factory>

</hibernate-configuration>

Snippets

public class Employee {
   private int id;
   private String firstName; 
   private String lastName;   
   private int salary;  

   public Employee() {}
   public Employee(String fname, String lname, int salary) {
      this.firstName = fname;
      this.lastName = lname;
      this.salary = salary;
   }
   
   public int getId() {
      return id;
   }
   
   public void setId( int id ) {
      this.id = id;
   }
   
   public String getFirstName() {
      return firstName;
   }
   
   public void setFirstName( String first_name ) {
      this.firstName = first_name;
   }
   
   public String getLastName() {
      return lastName;
   }
   
   public void setLastName( String last_name ) {
      this.lastName = last_name;
   }
   
   public int getSalary() {
      return salary;
   }
   
   public void setSalary( int salary ) {
      this.salary = salary;
   }
}

public class Employee {

private int id;

private String firstName;

private String lastName;

private int salary;

public Employee() {}

public Employee(String fname, String lname, int salary) {

this.firstName = fname;

this.lastName = lname;

this.salary = salary;

}

public int getId() {

return id;

}

public void setId( int id ) {

this.id = id;

}

public String getFirstName() {

return firstName;

}

public void setFirstName( String first_name ) {

this.firstName = first_name;

}

public String getLastName() {

return lastName;

}

public void setLastName( String last_name ) {

this.lastName = last_name;

}

public int getSalary() {

return salary;

}

public void setSalary( int salary ) {

this.salary = salary;

}

What is HQL?

HQL stand for Hibernate Query Language. Hibernate Query Language (HQL) is an object-oriented query language, similar to SQL, but instead of operating on tables and columns, HQL works with persistent objects and their properties. HQL queries are translated by Hibernate into conventional SQL queries.

The HQL query is created with syntax:
Read More

What are the core interfaces of Hibernate?

The core interfaces of Hibernate framework are:

Configuration
SessionFactory
Session
Query
Criteria
Transaction

What is hibernate?

Hibernate is an open-source and lightweight ORM tool that is used to store, manipulate, and retrieve data from the database.

How many types of association mapping are possible in hibernate?

Define persistent classes?

What are the key components of Hibernate?

What is ORM?

Hibernate Example Configuration File — hibernate.cfg.xml

Simple POJO Example – Employee

What is HQL?

What are the core interfaces of Hibernate?

What is hibernate?