Spring - 获取加载了惰性元素的实体页面

Question

我对 Spring 很陌生。

我正在尝试获取一个页面以将其返回到我的前端。 AppUser 与 Role 实体具有惰性关联。

我得到一个 failed to lazily initialize a collection of role 错误。

做了很多研究，但我不明白这个问题。

让我们看看代码：

AppUser 实体：

@Entity
@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@Table(name = "app_user")
public class AppUser {
    @Id
    @GeneratedValue
    @Column(name = "user_id")
    private UUID userId;

    @Column(name = "user_first_name")
    private String userFirstName;

    @Column(name = "user_last_name")
    @NonNull
    private String userLastName;

    @Column(name = "matricule")
    private String matricule;

    @Column(name = "email_address")
    private String emailAddress;

    @Column(name = "password")
    private String password;

    @EqualsAndHashCode.Exclude
    @ManyToOne
    @JoinColumn(name = "grade_id")
    private Grade grade;

    @EqualsAndHashCode.Exclude
    @ManyToMany
    @JoinTable(name = "user_role_association", joinColumns = @JoinColumn(name = "user_id"), 
inverseJoinColumns = @JoinColumn(name = "application_role_id"))
    private List<AppRole> appRoles;

控制器方法：

    @GetMapping(path = "user", produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<Page<AppUser>> getUserPage(@AuthenticationPrincipal UserDetail user,
                                                 @RequestParam("page") int page,
                                                 @RequestParam("size") int size,
                                                 @RequestParam(value = "sortDirection", 
required = false) String sortDirection,
                                                 @RequestParam(value = "sortField", required = 
false) String sortField) {
    log.info(String.format("User %s getting list of all users", user.getUsername()));
    try {
        final Page<AppUser> response = appUserService.getAll(page, size,sortDirection, 
sortField);
        return ResponseEntity.ok(response);
    } catch (Exception e) {
        log.error("Error fetching user page", e);
        throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "Error fetching data");
    }
}

服务方式：

    public Page<AppUser> getAll(int page,
                            int size,
                            String sortDirection,
                            String sortField) {
    Pageable pageable;
    Sort sort;
    // sorting & pagination
    if (sortField != null && !sortField.isEmpty()) {
        sort = Sort.by(sortField);
        if (sortDirection != null && sortDirection.equals("desc")) {
            sort = sort.descending();
        }
    } else {
        sort = Sort.by("matricule").descending();
    }
    pageable = PageRequest.of(page, size, sort);

    return appUserRepository.findAllAppUserWithAllProperties(pageable);
}

存储库

@Repository
public interface AppUserRepository extends JpaRepository<AppUser, UUID> {
Optional<AppUser> findByUserId(UUID uuid);
AppUser findByMatricule(String matricule);

@Query(value = "SELECT u FROM AppUser u LEFT JOIN FETCH u.appRoles WHERE u.matricule = 
:matricule")
AppUser findAppUserWithAppRolesByMatricule(String matricule);

@Query(value = "SELECT u FROM AppUser u LEFT JOIN u.appRoles")
Page<AppUser> findAllAppUserWithAllProperties(Pageable pageable);

}

查看日志我可以看到查询运行：

SQL - select appuser0_.user_id as user_id1_0_, appuser0_.email_address as email_ad2_0_, 
appuser0_.grade_id as grade_id7_0_, appuser0_.matricule as matricul3_0_, appuser0_.password as 
password4_0_, appuser0_.user_first_name as user_fir5_0_, appuser0_.user_last_name as 
user_las6_0_ from rixheim.app_user appuser0_ left outer join rixheim.user_role_association 
approles1_ on appuser0_.user_id=approles1_.user_id left outer join rixheim.application_role 
approle2_ on approles1_.application_role_id=approle2_.application_role_id order by 
appuser0_.matricule desc limit ?

所以我想我还没有办法检索完整的对象，但我现在真的被卡住了。

感谢您能在这件事上提供帮助。

谢谢。

Answer 1

终于找到了办法。

@EntityGraph(attributePaths = {"appRoles", "grade"})
@Query(value = "FROM AppUser appuser")
Page<AppUser> findAllAppUserWithAllProperties(Example example, Pageable 
pageable);

听起来使用 EntityGraph 将保持延迟加载，除非我们专门调用该查询。

Answer 2

懒惰的关联是故意的还是可以改变的？如果可以的话：

@EqualsAndHashCode.Exclude
@ManyToMany(fetch = FetchType.EAGER)
@JoinTable(name = "user_role_association", joinColumns = @JoinColumn(name = "user_id"), 
inverseJoinColumns = @JoinColumn(name = "application_role_id"))
private List<AppRole> appRoles;

如果不是，您可以通过显式调用来触发它们的加载，例如通过获取它们appUser.getAppRoles()。它不漂亮，但它应该可以工作。