what is entitymanager in spring boot code example

Example 1: spring boot entitymanager example

entityManager.getTransaction().begin();
		entityManager.remove(emp);
		entityManager.getTransaction().commit();

Example 2: spring boot entitymanager example

package com.frugalis.entity;
 
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
 
@Entity
@Table(name = "EMPLOYEE")
public class Employee {
	private int employeeId;
 
	private String name;
 
	@Id
	@Column(name = "EMPLOYEE_ID")
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	public int getEmployeeId() {
		return employeeId;
	}
 
	public void setEmployeeId(int employeeId) {
		this.employeeId = employeeId;
	}
 
	@Column(name = "EMPLOYEE_NAME")
	public String getName() {
		return name;
	}
 
	public void setName(String name) {
		this.name = name;
	}
 
	@Override
	public String toString() {
		return "Employee [ID=" + employeeId + ", Name=" + name + "]";
	}
 
}

Example 3: spring boot entitymanager example

//Select Query
List<Employee> emplList= entityManager.createQuery("SELECT e FROM Employee e").getResultList();

Example 4: spring boot entitymanager example

List<Employee> emplList= entityManager.createQuery("SELECT UPPER(e.name) FROM Employee e").getResultList();