Collection Mapping in Hibernate

 Collection Mapping in Hibernate

For Explanation watch Video ::

Directory Structure:

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>

<groupId>com.test</groupId>

<artifactId>CollectionMapping</artifactId>

<version>0.0.1-SNAPSHOT</version>

<packaging>jar</packaging>

<name>CollectionMapping</name>

<url>http://maven.apache.org</url>

<properties>

<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

<maven.compiler.source>1.9</maven.compiler.source>

<maven.compiler.target>1.9</maven.compiler.target>

</properties>

<dependencies>

<dependency>

<groupId>junit</groupId>

<artifactId>junit</artifactId>

<version>3.8.1</version>

<scope>test</scope>

</dependency>

<dependency>

<groupId>org.hibernate</groupId>

<artifactId>hibernate-core</artifactId>

<version>5.6.8.Final</version>

</dependency>

<dependency>

<groupId>org.projectlombok</groupId>

<artifactId>lombok</artifactId>

<version>1.18.20</version>

<scope>provided</scope>

</dependency>

<dependency>

<groupId>mysql</groupId>

<artifactId>mysql-connector-java</artifactId>

<version>8.0.22</version>

</dependency>

</dependencies>

</project>

HibernateUtil

package com.test.util;

import java.util.Properties;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.hibernate.cfg.Environment;

import com.test.entity.Employee;

public class HibernateUtil {

static SessionFactory factory = null;

static {

Configuration cfg = new Configuration();

Properties props = new Properties();

props.put(Environment.URL, "jdbc:mysql://localhost:3306/new");

props.put(Environment.USER, "root");

props.put(Environment.PASS, "root");

props.put(Environment.SHOW_SQL, true);

props.put(Environment.FORMAT_SQL, true);

props.put(Environment.HBM2DDL_AUTO, "update");

cfg.setProperties(props);

cfg.addAnnotatedClass(Employee.class);

factory = cfg.buildSessionFactory();

}

public static SessionFactory getSessionFactory() {

return factory;

}

public static Session getSession() {

return factory.openSession();

}

}

Employee

package com.test.entity;

import java.util.List;

import java.util.Map;

import java.util.Set;

import javax.persistence.CollectionTable;

import javax.persistence.Column;

import javax.persistence.ElementCollection;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.MapKeyColumn;

import javax.persistence.OrderColumn;

import javax.persistence.Table;

import lombok.AllArgsConstructor;

import lombok.Data;

import lombok.NoArgsConstructor;

@Data

@AllArgsConstructor

@NoArgsConstructor

@Entity

@Table(name = "emptab")

public class Employee {

@Id

private Integer id;

private String name;

@ElementCollection

@CollectionTable(

name = "emp_friends",

joinColumns= @JoinColumn(name = "eid")

)

@Column(name="friendName")

@OrderColumn(name = "pos")

private List<String> friends;

@ElementCollection

@CollectionTable(

name = "emp_cards",

joinColumns= @JoinColumn(name = "eid")

)

@Column(name="cno")

@MapKeyColumn(name = "cname")

private Map<String,String> cards;

@ElementCollection

@CollectionTable(

name = "emp_projs",

joinColumns= @JoinColumn(name = "eid")

)

@Column(name = "projName")

private Set<String> projs;

}

App

package com.test;

import java.util.Arrays;

import java.util.List;

import java.util.Map;

import java.util.Set;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import com.test.entity.Employee;

import com.test.util.HibernateUtil;

/**

 * Hello world!

 *

 */

public class App 

{

    public static void main( String[] args )

    {

    //get the SessionFactory Obj

    SessionFactory factory = HibernateUtil.getSessionFactory();

    //set the Session Obj

    Session ses = HibernateUtil.getSession();

    try(factory;ses){

   

    //list of friends

    List<String> list = Arrays.asList("Angela","Carla");

   

    //create the Map

    Map<String,String> map = Map.of("aadhar","123","pan","mk12");

   

    //create the set for projects

    Set<String> set = Set.of("p1","p2");

   

    //create the emp Obj

    Employee emp = new Employee(101,"sam",list,map,set);

   

    //save 

    //begin the tx

    ses.beginTransaction();

   

    ses.save(emp);

   

    //commit the tx

    ses.getTransaction().commit();

    }

    }

}