Entity Lifecycle

 

1.

package com.appsdeveloperblog.ws.demo_transactional;

import com.appsdeveloperblog.ws.demo_transactional.entity.Account;
import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@RequiredArgsConstructor
public class DemoTransactionalApplication implements CommandLineRunner {

    private final EntityManagerFactory emf;

    public static void main(String[] args) {
        SpringApplication.run(DemoTransactionalApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        // Transient mode: because it does not exist in DB
        Account account = new Account();
        // Managed mode: because it is in realm of Persistence Context
        em.persist(account);
        em.getTransaction().commit();
        em.close();
    }

}

2. 

package com.appsdeveloperblog.ws.demo_transactional;

import com.appsdeveloperblog.ws.demo_transactional.entity.Account;
import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@RequiredArgsConstructor
public class DemoTransactionalApplication implements CommandLineRunner {

    private final EntityManagerFactory emf;

    public static void main(String[] args) {
        SpringApplication.run(DemoTransactionalApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        // Managed mode: because it retrieves it from DB
        Account account = em.find(Account.class, 3L);
        account.setBalance(100);
        // Detached mode: not in realm of Persistence Context
        em.remove(account);
        account.setName("Parvin");
//        em.persist(account);
        em.getTransaction().commit();
        em.close();
    }

}

3. flush()

package com.appsdeveloperblog.ws.demo_transactional;

import com.appsdeveloperblog.ws.demo_transactional.entity.Account;
import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@RequiredArgsConstructor
public class DemoTransactionalApplication implements CommandLineRunner {

    private final EntityManagerFactory emf;

    public static void main(String[] args) {
        SpringApplication.run(DemoTransactionalApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        // Managed mode: because it retrieves it from DB
        Account account = em.find(Account.class, 4L);
        account.setBalance(500);
        // Detached mode: not in realm of Persistence Context
        em.flush();
        em.detach(account);
        em.getTransaction().commit();
        em.close();
    }

}

4. *

ther is great difference between:

package com.appsdeveloperblog.ws.demo_transactional;

import com.appsdeveloperblog.ws.demo_transactional.entity.Account;
import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@RequiredArgsConstructor
public class DemoTransactionalApplication implements CommandLineRunner {

    private final EntityManagerFactory emf;

    public static void main(String[] args) {
        SpringApplication.run(DemoTransactionalApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        Account account = em.find(Account.class, 4L);
        account.setName("first");
        em.flush();
        em.detach(account);
        em.merge(account);
        account.setName("second");
        em.flush();
        em.getTransaction().commit();
        em.close();
    }

}

and

package com.appsdeveloperblog.ws.demo_transactional;

import com.appsdeveloperblog.ws.demo_transactional.entity.Account;
import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import lombok.RequiredArgsConstructor;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@RequiredArgsConstructor
public class DemoTransactionalApplication implements CommandLineRunner {

    private final EntityManagerFactory emf;

    public static void main(String[] args) {
        SpringApplication.run(DemoTransactionalApplication.class, args);
    }

    @Override
    public void run(String... args) throws Exception {
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        Account account = em.find(Account.class, 4L);
        account.setName("first");
        em.flush();
        em.detach(account);
        account = em.merge(account);
        account.setName("second");
        em.flush();
        em.getTransaction().commit();
        em.close();
    }

}