Java Spring ManyToOne 如何加载唯一引用

Question

我在 Spring 中保存了员工和“个人发展计划”的数据。可以说，员工是统治类(Class)。它看起来像这样:

@Entity(name = "employee")
@Table(name = "EMPLOYEE")
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "EMPLOYEE_ID")
    private int id;

    // etc...
}

个人发展计划如下所示:

@Entity(name = "pdp")
@Table(name = "PDP")
public class PersonalDevelopmentPlan implements Serializable {

    @Id
    @GeneratedValue
    @Column(name = "PDP_ID")
    private int id;

    @ManyToOne(optional = false)
    @JoinColumn(name = "EMPLOYEE_ID")
    private Employee employee;

    // etc..
}

在数据库中，它存储为来自 PDP -> Employee 的外键引用。

我希望能够加载数据库中的 PDP，仅包含员工 ID，但我总是获得包含所有属性的整个 Employee 对象。我该怎么做？

我尝试了 @ManyToOne(fetch = FetchType.Lazy) 但这在获取时出现以下错误:

Type definition error: [simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->nl.kars.lms.model.pdp.PersonalDevelopmentPlan["employee"]->nl.kars.lms.model.Employee$HibernateProxy$AAwzPX4I["hibernateLazyInitializer"])

我做错了什么？

Answer 1

如果您只想要 ID，为什么不映射它而没有关系呢？

@Entity(name = "pdp")
@Table(name = "PDP")
public class PersonalDevelopmentPlan implements Serializable {

    @Id
    @GeneratedValue
    @Column(name = "PDP_ID")
    private int id;

    @Column(name = "EMPLOYEE_ID")
    private Long employeeId;

    // etc..
}