"Welcome To Ashok IT"				
			                     "Spring Boot and MicroServices"
                                               Topic : Spring Data JPA - Generators
                                              	 Date  : 11/10/2024
                                                  (Session - 43)                  
_____________________________________________________________________________________________________________________________
Today Session
==============

***************************
3) GenerationType.Identity
***************************
* In this type of generation Hibernate always generate the value for primary key column based on auto increment feature.

* Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table.

* This Identity generation can be used for auto increment feature supported databases only.

* This Identity generation can't be used for Oracle Database but we can use for following database like                   MYSQL,SQLServer,PostgreSQL,MSACCESS etc.,

   Example
   =======
        @Id
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        private Integer customerId;

NOTE
====
* Make sure We need to test this Identity Strategy in MySQL Database Software.

* If we are doing the testing with Oracle Database will get error "doesnot support the identity key generation".


Example Application
===================
package com.ashokit.enities;

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

@Entity
@Table(name="mahesh_banks")
public class Bank {	
	
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Integer bankId;
	
	private String bankName;
	
	private String location;

	public Integer getBankId() {
		return bankId;
	}

	public void setBankId(Integer bankId) {
		this.bankId = bankId;
	}

	public String getBankName() {
		return bankName;
	}

	public void setBankName(String bankName) {
		this.bankName = bankName;
	}

	public String getLocation() {
		return location;
	}

	public void setLocation(String location) {
		this.location = location;
	}

	@Override
	public String toString() {
		return "Bank [bankId=" + bankId + ", bankName=" + bankName + ", location=" + location + "]";
	}
}


Steps
=====
1) When we running application defintely will get an error feature not supporting in Oracle Database.

2) To Test this application in smooth manner required MYSQL Database internally will create table with given name 

     create table mahesh_banks(bank_id bigint primary key auto_increment,bank_name varchar(255),location varchar(255));

************************
4) GenerationType.TABLE
************************
* In this type of generation Hibernate internally maintains one table to hold the primary keys of all tables in the database.

* In this case the generation table is created by Hibernate with name hibernate_sequences and there will be two column in the   table i.e.,sequence_name and next_value

  Example-1: Default Behaviour
  ============================
     @GeneratedValue(strategy=GenerationType.TABLE)

   1) Hibernate Internally will create following table i.e.,hibernate_sequences and will create following columns i.e.,
      sequence_name, next_val
   
      Hibernate: create table hibernate_sequences (sequence_name varchar2(255 char) not null, next_val number(19,0),                           primary key (sequence_name))

   2) Hibernate will insert one row information about entity as below
    
      Hibernate: insert into hibernate_sequences(sequence_name, next_val) values ('default',0)
   
   3) Hibernate will select value from hibernate_sequences table based on sequence name as below
      
      Hibernate: select tbl.next_val from hibernate_sequences tbl where tbl.sequence_name=? for update

   4) Hibernate will perform update operation after selecting current value based on sequence name
 
      Hibernate: update hibernate_sequences set next_val=?  where next_val=? and sequence_name=?

   5) Hibernate will perform insert operation on entity 
   
      Hibernate: insert into mahesh_students (course_fee, course_name, student_name, student_id) values (?, ?, ?, ?)

   PROBLEM
   =======
   * The entry which is inserted into hibernate_sequence table will be reused for multiple tables that will leads to 
     order problem of primary key column to overcome need to generate entry for each table in hibernate_sequence table (or)our           own custom table.

  Example-2 : We can create our own table name, column name,
  =========
    @GeneratedValue(strategy=GenerationType.TABLE, generator="customers")
    @TableGenerator(
        name="customers",
        table="sequence_store",
        pkColumnName = "seq_name",
        valueColumnName = "seq_value",
        pkColumnValue="customers_seq_id",
        initialValue=1,
        allocationSize=1
    )
    private Integer customerId;

   1) Created the table with name i.e.,sequence_store and following two columns i.e.,seq_name, seq_value.

   2) Inserted record per table based on primary key column value with initial value
          
           sequence_store
           **************
            seq_name                  seq_value
            *********                 **********
            customers_seq_id             1
            students_seq_id              1
            employees_seq_id             1
            products_seq_id              1

    3)  When We are performing insert operation on particular entity the respective entry seq_value value will be
        selected and updated the next value as well.

          Ex: If we are performing insert operation on customer entity object then follow queries will be executed

        Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
        Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?

    4)  Performing the Actual Insert Query.

        Hibernate: insert into mahesh_students (course_fee, course_name, student_name, student_id) values (?, ?, ?,?)

===================
Example Application
===================

Bike.java
=========
package com.ashokit.enities;

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

@Entity
@Table(name = "mahesh_bikes")
public class Bike {
	
	@Id
	@GeneratedValue(strategy = GenerationType.TABLE,generator = "bikes")
	@TableGenerator(name ="bikes",
	                table = "sequence_store",
	                pkColumnName = "seq_name",
	                valueColumnName = "seq_value",
	                pkColumnValue = "bike_id",
	                initialValue = 1,
	                allocationSize = 1)
	private int bikeId;
	
	private String bikeName;
	
	private Integer cost;

	public Integer getBikeId() {
		return bikeId;
	}

	public void setBikeId(Integer bikeId) {
		this.bikeId = bikeId;
	}

	public String getBikeName() {
		return bikeName;
	}

	public void setBikeName(String bikeName) {
		this.bikeName = bikeName;
	}

	public Integer getCost() {
		return cost;
	}

	public void setCost(Integer cost) {
		this.cost = cost;
	}

	@Override
	public String toString() {
		return "Bike [bikeId=" + bikeId + ", bikeName=" + bikeName + ", cost=" + cost + "]";
	}
	
}


Employee.java
=============
package com.ashokit.enities;

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

@Entity
@Table(name="mahesh_employees")
public class Employee {
	
	@Id
	@GeneratedValue(strategy = GenerationType.TABLE,generator = "employees")
	@TableGenerator(name ="employees",
	                table = "sequence_store",
	                pkColumnName = "seq_name",
	                valueColumnName = "seq_value",
	                pkColumnValue = "employee_id",
	                initialValue = 1,
	                allocationSize = 1)
	private Integer employeeId;
	
	private String employeeName;

	public Integer getEmployeeId() {
		return employeeId;
	}

	public void setEmployeeId(Integer employeeId) {
		this.employeeId = employeeId;
	}

	public String getEmployeeName() {
		return employeeName;
	}

	public void setEmployeeName(String employeeName) {
		this.employeeName = employeeName;
	}

	@Override
	public String toString() {
		return "Employee [employeeId=" + employeeId + ", employeeName=" + employeeName + "]";
	}

}

EmployeeDao.java
================
package com.ashokit.dao;

import org.springframework.data.repository.CrudRepository;

import com.ashokit.enities.Employee;

public interface EmployeeDao extends CrudRepository<Employee, Integer> {

}


BikeDao.java
============
package com.ashokit.dao;

import org.springframework.data.repository.CrudRepository;

import com.ashokit.enities.Bike;

public interface BikeDao extends CrudRepository<Bike, Integer> {

}

Application.java
================
package com.ashokit;

import java.util.Arrays;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import com.ashokit.dao.BikeDao;
import com.ashokit.dao.CustomerDao;
import com.ashokit.dao.EmployeeDao;
import com.ashokit.dao.ProductDao;
import com.ashokit.dao.VehicleDao;
import com.ashokit.enities.Bike;
import com.ashokit.enities.Employee;
import com.ashokit.enities.Product;
import com.ashokit.enities.Vehicle;

import net.bytebuddy.utility.nullability.UnknownNull;

@SpringBootApplication
public class Application implements CommandLineRunner{
	
	@Autowired
	private BikeDao bikeDao;
	
	@Autowired
	private EmployeeDao employeeDao;

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}
	
	@Override
	public void run(String... args) throws Exception {
		
		Employee e1 = new Employee();
		e1.setEmployeeName("Mahesh"); //3 & 4
		
		Employee e2 = new Employee();
		e2.setEmployeeName("Rajesh");
		
		Iterable<Employee> savedEmployee = employeeDao.saveAll(Arrays.asList(e1,e2));
		savedEmployee.forEach(emp-> System.out.println(emp));		
		
		Bike b1 = new Bike();
		b1.setBikeName("Access"); //5 && 6
		b1.setCost(100000);
		
		Bike b2 = new Bike();
		b2.setBikeName("Activa");
		b2.setCost(200000);
		
		Iterable<Bike> savedBikes = bikeDao.saveAll(Arrays.asList(b1,b2));
		savedBikes.forEach(bike -> System.out.println(bike));	
	}
}

OUTPUT
======


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

Hibernate: create table ashokit_students (student_id number(10,0) not null, contact_no varchar2(255 char), eamil_id varchar2           (255 char), name varchar2(255 char), primary key (student_id))
Hibernate: create table sequence_store (seq_name varchar2(255 char) not null, seq_value number(19,0), primary key (seq_name))
Hibernate: insert into sequence_store(seq_name, seq_value) values ('customers_seq_id',1)
Hibernate: insert into sequence_store(seq_name, seq_value) values ('students_seq_id',1)
Hibernate: create table shopping_customers (customer_id number(10,0) not null, customer_contact_no varchar2(255 char), 	   customer_email varchar2(255 char), customer_location varchar2(255 char), customer_name varchar2(255 char), primary 	   key (customer_id))

Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: insert into shopping_customers (customer_contact_no,customer_email,customer_location,customer_name,customer_id) values (?,?,?,?,?)
Hibernate: insert into shopping_customers (customer_contact_no,customer_email,customer_location,customer_name,customer_id) values (?,?,?,?,?)
Hibernate: insert into shopping_customers (customer_contact_no,customer_email,customer_location,customer_name,customer_id) values (?,?,?,?,?)
Hibernate: insert into shopping_customers (customer_contact_no,customer_email,customer_location,customer_name,customer_id) values (?,?,?,?,?)
Hibernate: insert into shopping_customers (customer_contact_no,customer_email,customer_location,customer_name,customer_id) values (?,?,?,?,?)
ShoppingCustomer [custId=2, name=Mahesh, location=Hyderabad, email=mahesh.ashokit@gmail.com, contactNo=123456789]
ShoppingCustomer [custId=3, name=Suresh, location=Pune, email=suresh.ashokit@gmail.com, contactNo=545454454]
ShoppingCustomer [custId=4, name=Rajesh, location=Chennai, email=rajesh.ashokit@gmail.com, contactNo=23323232]
ShoppingCustomer [custId=5, name=Ramesh, location=Hyderabad, email=ramesh.ashokit@gmail.com, contactNo=121212121]
ShoppingCustomer [custId=6, name=Nagesh, location=Hyderabad, email=nagehsh.ashokit@gmail.com, contactNo=3434211123]
Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: select tbl.seq_value from sequence_store tbl where tbl.seq_name=? for update
Hibernate: update sequence_store set seq_value=?  where seq_value=? and seq_name=?
Hibernate: insert into ashokit_students (contact_no,eamil_id,name,student_id) values (?,?,?,?)
Hibernate: insert into ashokit_students (contact_no,eamil_id,name,student_id) values (?,?,?,?)
Student [studentId=2, studentName=Mahesh, studentEmail=mahesh.ashokit@gmail.com, contactNo=1232323]
Student [studentId=3, studentName=Ashok, studentEmail=ashokitschools@gmail.com, contactNo=2323232]

****************
sequence_store
****************
seq_name                     seq_value
*********                    **********
employee_id	                5
bike_id                 	5