插入子记录时Hibernate映射错误

Question

我有两个实体类，如下所示-

public class Parent {

    @Id
    private Integer parentId;
    private String name;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "parent", cascade = CascadeType.ALL)
    private List<Child> children;
}
public class Child {

    @Id
    private Integer childId;
    private String name;
    
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "parentId", insertable = false, updatable = true, nullable = false)
    private Parent parent;
}

@RestController
public class ParentController {

    @Autowired
    private ParentRepo repo;

    @GetMapping("/parent")
    public void get() {
        Child c1 = Child.builder().childId(1).name("s1").build();
        Child c2 = Child.builder().childId(2).name("s2").build();
        List<Child> children = new ArrayList<>();
        children.add(c1);
        children.add(c2);
        Parent parent = Parent.builder().parentId(1).name("PARENT")
                .children(children)
                .build();
        Parent savedParent = repo.save(parent);
}
}

Tables -

CREATE TABLE public.parent
(
    parent_id integer NOT NULL,
    name character varying(255) COLLATE pg_catalog."default",
    CONSTRAINT parent_pkey PRIMARY KEY (parent_id)
)WITH (
    OIDS = FALSE
)
TABLESPACE pg_default;

CREATE TABLE public.child
(
    child_id integer NOT NULL,
    name character varying(255) COLLATE pg_catalog."default",
    parent_id integer NOT NULL,
    CONSTRAINT child_pkey PRIMARY KEY (child_id),
    CONSTRAINT fk7dag1cncltpyhoc2mbwka356h FOREIGN KEY (parent_id)
        REFERENCES public.parent (parent_id) MATCH SIMPLE
        ON UPDATE NO ACTION
        ON DELETE NO ACTION
)
WITH (
    OIDS = FALSE
)
TABLESPACE pg_default;

我在保存子记录时出错。

错误-

Hibernate：插入子（名称，child\u id）值（？，）2022-07-19 23:12:31.727警告20940---[nio-8080-exec-2]o.h.engine.jdbc.spi。SqlExceptionHelper:SQL错误：0，SQLState:23502 2022-07-19 23:12:31.727错误20940---[nio-8080-exec-2]o.h.engine.jdbc.spi。SqlExceptionHelper：错误：“parent\u id”列中的null值违反了非null约束详细信息：失败的行包含（1，s1，null）。2022-07-19 23:12:31.728信息20940---[nio-8080-exec-2]o.h.e.j.b.内部。AbstractBatchImpl:hh000010:batch发布时，它仍然包含JDBC语句2022-07-19 23:12:31.754错误20940-[nio-8080-exec-2]o.a.c.c.c.[/]。[dispatcherServlet]：Servlet。路径为[]的上下文中servlet[dispatcherServlet]的service（）引发异常[Request processing failed；嵌套异常为org.springframework.dao.DataIntegrityViolationException:无法执行语句；SQL[n/a]；约束[parent_id]；嵌套异常为org.hibernate.exception。ConstraintViolationException：无法执行具有根本原因的语句]

org.postgresql.util.PSQLException：ERROR：列"parent_id"中的空值违反了非空约束详细信息：失败的行包含（1， s1， null）。

不确定hibernate将如何拾取外键并将其分配给子级。

Answer 1

你得先设置双向关系

public class Parent {

     @Id
     private Integer parentId;
     private String name;

     @OneToMany(fetch = FetchType.LAZY, mappedBy = "parent", cascade = CascadeType.ALL)
     private List<Child> children;

     public void addChild(Child child) {
           this.children.add(child);
           child.setParent(this);
     }
}

并通过该方法添加孩子。