Question

我正在将Spring Data Rest用于Department-Employee关系，如下所示，并且在Employee上定义了RepositoryRestResource。

class Department {
  @Id
  UUID Id;

  String name;

  @OneToMany(mappedBy = "employee", targetEntity = Employee.class, cascade = {CascadeType.ALL}, fetch = FetchType.LAZY)
  @RestResource(exported = false)
  private Set<Employee> employees;

}


class Employee {
  @Id
  UUID Id;

  String firstName;

  String lastName;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "dept_ref")
  @RestResource(exported = false)
  private Department department;
}

@Projection(name = "employeeProjection", types = {Employee.class})
interface EmployeeProjection {
  String getFirstName();
  String getLastName();
}


@RepositoryRestResource(excerptProjection = EmployeeProjection.class)
public interface EmployeeRepository extends CrudRepository<Employee, UUID> {

  //this doesn't work
  @Query(value = "SELECT emp.firstName as firstName , emp.lastName as lastName FROM Employee emp JOIN emp.department "
          + "WHERE emp.department.name = :departmentName ")
  List<EmployeeProjection> findByDepartmentName(@Param("departmentName") String departmentName); 


  //this works
  List<EmployeeProjection> findByFirstName(@Param("firstName") String firstName);

}

问题是当我以findByDepartmentName执行联接搜索时，出现以下错误。

2019-07-01 00:26:33.300 ERROR 7396 --- [nio-8443-exec-5] o.s.d.r.w.RepositoryRestExceptionHandler : PersistentEntity must not be null!

java.lang.IllegalArgumentException: PersistentEntity must not be null!
        at org.springframework.util.Assert.notNull(Assert.java:134)
        at org.springframework.data.rest.webmvc.PersistentEntityResource$Builder.<init>(PersistentEntityResource.java:140)

Answer 1

通过将返回类型从List<Employee>更改为List<EmployeeProjection>来解决了问题，它仍然以excerptProjection的形式返回投影。不知道为什么Spring Data Rest会期望这样做，但是它可以工作。

List<Employee> findByDepartmentName(@Param("departmentName") String departmentName);

Spring Data Rest：按父列进行的JOIN搜索引发错误（o.s.d.r.w.RepositoryRestExceptionHandler：PersistentEntity不能为null！）

1 个答案: