JPA/Hibernate中一对一关联时不持有外键方的属性延迟加载为什么不生效？

若鱼19192026-04-11 13:25

问题

现在有2个实体：Author、Contact，关系是一对一，Contact表负责维护关联关系，如图：

实体定义如下：

Author

java 复制代码

public class Author {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    @OneToOne(fetch = FetchType.LAZY, mappedBy = "author")
    private Contact contact;
}

Contact

java 复制代码

public class Contact {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String mobile;
    private String email;
    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn( name = "author_id",referencedColumnName = "id")
    private Author author;
}

现在有一个需求，要根据authorId查询author，但是不需要把author关联的contact也查出来，虽然我们这里配置了延迟加载contact，但是实际查询的时候，还是把contact查出来了，如下：

java 复制代码

@Transactional(readOnly = true)
public AuthorVO getById(Long id) {
   return authorRepository.findById(id)
           .map(author -> new AuthorVO(author.getId(), author.getName()))
           .orElse(null);
}

SQL日志：

java 复制代码

Hibernate: select a1_0.id,a1_0.name from author a1_0 where a1_0.id=?
Hibernate: select c1_0.id,c1_0.author_id,c1_0.email,c1_0.mobile from contact c1_0 where c1_0.author_id=?

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