Delete Data From Many-to-many Relationship

CustomerEntity class

@Entity(name = "CUSTOMER")

public class CustomerEntity {

   @Id

   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "customerid-gen")

   @SequenceGenerator(name = "customerid-gen", sequenceName = "CUSTOMER_SEQ", 

      allocationSize = 1, initialValue = 0)

   @Column(name = "CUSTOMER_ID")

   private Integer id;

   private String customerName;

   @ManyToMany(cascade ={CascadeType.ALL})

   @JoinTable(name = "CUST_PHONE", 

      joinColumns = @JoinColumn(name = "CUSTOMER_ID", 

                                 referencedColumnName = "CUSTOMER_ID"), 

   inverseJoinColumns = @JoinColumn(name = "PHONE_ID", 

                                 referencedColumnName = "PHONE_ID"))

   private List<PhoneNumberEntity> phones = new ArrayList<PhoneNumberEntity>();

}

PhoneNumberEntity class

@Entity(name = "PHONE")

public class PhoneNumberEntity {

   @Id

   @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "phoneid-gen")

   @SequenceGenerator(name = "phoneid-gen", sequenceName = "PHONE_SEQ", 

      allocationSize = 1, initialValue = 0)

   @Column(name = "PHONE_ID")

   private Integer id;

   private String phNumber;

   @ManyToMany(cascade ={CascadeType.ALL})

   @JoinTable(name = "CUST_PHONE", joinColumns = @JoinColumn(name = "PHONE_ID",

                   referencedColumnName = "PHONE_ID"),

              inverseJoinColumns = @JoinColumn(name = "CUSTOMER_ID", 

                     referencedColumnName = "CUSTOMER_ID"))

   private List<CustomerEntity> customers;

}

Testing class

CustomerEntity entity = new CustomerEntity("Shambhu");

entity.getPhones().add(new PhoneNumberEntity("(8837199181"));

entity.getPhones().add(new PhoneNumberEntity("(8981518899"));

Integer id = emService.persistCustomer(entity);

             

CustomerEntity customerEntity=emService.findCustomerById(id);

             

List<PhoneNumberEntity> phones= customerEntity.getPhones();

             

for(PhoneNumberEntity entity2:phones){

       System.out.println("Deleting phone id :"+entity2.getId());

       emService.deletePhone(entity2.getId());

       //break;

}

Sequence generator

There are different ways to generate sequence
1) Automatic
2) Custom

1) Automatic

@Id

@GeneratedValue(strategy = GenerationType.SEQUENCE,generator= "countryid-gen")

@SequenceGenerator(name = "countryid-gen", sequenceName = "COUNTRY_SEQ",

              allocationSize = 1, initialValue = 0)

@Column(name = "COUNTRY_ID")

private int id;

2) Custom 

First need to create 

a) Custom Class, then 

b) implement that custom class.

a) Custom Class

package com.pristine.util;

import java.io.Serializable;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import org.apache.commons.lang3.StringUtils;

import org.hibernate.HibernateException;

import org.hibernate.engine.spi.SessionImplementor;

import org.hibernate.id.IdentifierGenerator;

public class EmployeeCodeGenerator implements IdentifierGenerator {

    public Serializable generate(SessionImplementor session, Object object)

            throws HibernateException {

        String prefix = "E";

        Connection connection = session.connection();

        try {

            PreparedStatement ps = connection

                    .prepareStatement("SELECT nextval ('EMPLOYEE_SEQ') as nextval");

            ResultSet rs = ps.executeQuery();

            if (rs.next()) {

                int id = rs.getInt("nextval");

                String code = prefix + StringUtils.leftPad("" + id,3, '0');

                return code;

            }

        } catch (SQLException e) {

            throw new HibernateException(

                    "Unable to generate Stock Code Sequence");

        }

        return null;

    }

}

b) Implementation of Custom Class

@Id

@GenericGenerator(name="seq_id", strategy="com.pristine.util.EmployeeCodeGenerator")

@GeneratedValue(generator="seq_id")

@Column(name = "ID", nullable = false)

private String id;

Hibernate Error

Invocation of init method failed; nested exception is org.hibernate.MappingException: Could not determine type for: java.util.List, at table: Country_master, for columns: [org.hibernate.mapping.Column(stateMasters)]

Add
<dependency>
   <groupId>org.hibernate</groupId>
   <artifactId>hibernate-entitymanager</artifactId>
   <version>${hibernate.version}</version>
</dependency>

=======================================================

Invocation of init method failed; nested exception is java.lang.NoSuchMethodError: javax.persistence.OneToMany.orphanRemoval()Z

That may be due to hibernate-jpa-2.0-api.jar

Add Below code
<dependency>
   <groupId>org.hibernate</groupId>
   <artifactId>hibernate-entitymanager</artifactId>
   <version>${hibernate.version}</version>
   <exclusions>
      <exclusion>
         <groupId>org.hibernate.javax.persistence</groupId>
 <artifactId>hibernate-jpa-2.0-api</artifactId>
      </exclusion>
   </exclusions>
</dependency>


========================================================

Caused by: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.pristine.domain.StateMasterEntity


@OneToMany(cascade = CascadeType.ALL)

onetomany mapping with example

@Entity

@Table(name = "AUTHOR")

public class Author {

       private long id;

       private String name;

       private String email;

      

       public Author() {

       }

                    

       public Author(String name, String email) {

              this.name = name;

              this.email = email;

       }

       @Id

       @Column(name = "AUTHOR_ID")

       @GeneratedValue(strategy=GenerationType.AUTO)

       public long getId() {

              return id;

       }

//setter/getter

}

@Entity

@Table(name = "BOOK")

public class Book {

       private long id;

       private String title;

       private String description;

       private Date publishedDate;

      

       private List<Author> author = new ArrayList<Author>();

       public Book() {

       }

       @Id

       @Column(name = "BOOK_ID")

       @GeneratedValue(strategy=GenerationType.AUTO)

       public long getId() {

              return id;

       }

       @Temporal(TemporalType.DATE)

       @Column(name = "PUBLISHED")

       public Date getPublishedDate() {

              return publishedDate;

       }

       @OneToMany(cascade = CascadeType.ALL)

       @JoinColumn(name = "BOOK_ID")

       public List<Author> getAuthor() {

              return author;

       }

//setter/getter

}

public class BooksTest {

       public static void main(String[] args) {

              SessionFactory sessionFactory = HibernateUtils.getSessionFactory();

              Session session = sessionFactory.openSession();

              try{

                     session.beginTransaction();

                    

                     // creates a Book entity

                     Book newBook = new Book();

                     newBook.setTitle("Pro PHP MVC");

                     newBook.setDescription("Php MVC Book");

                     newBook.setPublishedDate(new Date());

                     List<Author> authors= new ArrayList<Author>();

                     authors.add(new Author("Shambhu Kumar", "shambhu@gmail.com"));

                     authors.add(new Author("Ravi Kumar", "Ravi@gmail.com"));

                     newBook.setAuthor(authors);

                    

                     // persists the book entity

                     Long bookId = (Long) session.save(newBook);

                    

                     // gets the book entity back

                     Book book = (Book) session.get(Book.class, bookId);

                     System.out.println("Book's Title: " + book.getTitle());

                     System.out.println("Book's Description: " + book.getTitle());

                    

                    

                     book.getAuthor().add(new Author("Shambhu1", "shambhu@gmail.com"));

                     book.getAuthor().add(new Author("Ravi1", "Ravi@gmail.com"));

                    

                     session.update(book);

                     List<Author> authorsList = book.getAuthor();

                     for(Author author:authorsList){

                           System.out.println("Name: " + author.getName());

                           System.out.println("Mail: " + author.getEmail());     

                     }

                    

              }

             

              finally{

                     session.getTransaction().commit();

                     session.close();    

                     sessionFactory.close();

              }

             

                    

       }

}