Question

我有实体跟随实体：
Employee extends Person
Company有List<Employee>（延迟加载）。

当我尝试使用Hibernate.initialize(company.getEmployees());初始化员工列表时，我收到错误，因为hibernate并不了解Employee是Person。

Person.java

@Entity
@Table(name = "person")
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class Person implements java.io.Serializable {
    @Column(name = "person_id")
    protected Long personId;

    @Column(name = "name")
    protected String name;

    @Column(name = "age")
    protected String age;
}

Employee.java

@Entity
@Table(name = "employee")
@PrimaryKeyJoinColumn(name = "person_id")
public class Employee extends Person {
    @Column(name = "employee_number")
    private String number;

    @ManyToOne
    @JoinColumn(name = "company_id")
    private Company company;
}

Company.java

@Entity
@Table(name = "company")
public class Company implements java.io.Serializable {
    @Column(name = "company_id")
    protected String id;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "company", cascade = CascadeType.ALL)
    @OrderBy(clause = "name desc")
    protected List<Employee> employees = new ArrayList<Employee>();
}


Hibernate.initialize(company.getEmployees());

例外：

org.postgresql.util.PSQLException: ERROR: column employee0_.name does not exist
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2102)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1835)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)

对于这种情况，是否存在延迟加载的解决方案？

Answer 1

员工与人之间肯定存在一对一的关系。通过在Java中分割对象而不是在表中分割对象是有意义的。我认为Employee表应该在person表中定义名称和其他列以简化设计。

懒加载“JOINED”集合

1 个答案: