Fetching in hibernate

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It is recommended to use FetchType.LAZY. Join fetch the columns when they are needed.

Below is an Employer entity class which is mapped to the table employer. As you can see I used fetch = FetchType.LAZY instead of fetch = FetchType.EAGER. The reason I am using LAZY is because Employer may have a lot of properties later on and every time I may not need to know all the fields of an Employer, so loading all of them will leading a bad performance then an employer is loaded.

@Entity
@Table(name = "employer")
    public class Employer  
    {  
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long id;
    
        @Column(name = "name")
        private String Name;

        @OneToMany(mappedBy = "employer", fetch = FetchType.LAZY,
               cascade = { CascadeType.ALL }, orphanRemoval = true)
        private List<Employee> employees;
  
        public Long getId() {  
            return id;  
        }

        public void setId(Long id) {  
            this.id = id;  
        }

        public String getName() {  
            return name;  
        }

        public void setName(String name) {  
            this.name = name;  
        }

        public List<Employee> getEmployees() {  
            return employees;  
        }

        public void setEmployees(List<Employee> employees) {  
            this.employees = employees;  
        }  
    }  

However, for LAZY fetched associations, uninitialized proxies are sometimes leads to LazyInitializationException. In this case, we can simply use JOIN FETCH in the HQL/JPQL to avoid LazyInitializationException.

SELECT Employer employer FROM Employer
       LEFT JOIN FETCH employer.name
       LEFT JOIN FETCH employer.employee employee 
       LEFT JOIN FETCH employee.name
       LEFT JOIN FETCH employer.address

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