Easy pagination with Spring JPA - Hibernate

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File Main
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for (theUser in userService.getUsersByClassification("Class 1", pageNr = 0, pageSize = 10)) {
	println(theUser.displayName)
}


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File UserService
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@Service
class UserService @Autowired constructor(private val userPaging: UserPagingAndSortingRepository) {
    fun getUsersByClassification(classification: String, pageNr: Int, pageSize: Int): Page<User> {
        val pageable: Pageable = PageRequest.of(pageNr, pageSize)
        return userPaging.findByClassification(classificatie, pageable)
    }
}


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File UserPagingAndSortingRepository
The Query annotation is JPQL, but in the case of JPA Hibernate, can also be HQL.
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interface UserPagingAndSortingRepository : PagingAndSortingRepository<User, Long> {
    @Query("SELECT u FROM User u JOIN u.userExtradata um WHERE um.classification = :classification")
    fun findByClassification(@Param("classification") classification: String, pageable: Pageable): Page<User>
}


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File entity.User
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@Entity
@Table(name = "\"user\"")
class User {
    @Id
    var id: Long = 0;

    @Column (name="display_name")
    var displayName: String = ""

    @OneToOne(mappedBy = "user", cascade = [CascadeType.ALL], fetch = FetchType.LAZY)
    val userExtradata: UserExtradata? = null
}


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File entity.UserExtradata
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@Entity
@Table(name = "\"user_extradata\"")
class UserExtradata {
    @Id
    var user_id: Long = 0;
    var classification: String = ""
    var phonenumber: String? = ""

    @OneToOne
    @JoinColumn(name = "user_id", referencedColumnName = "id")
    val user: User? = null
}