java - OneToMany 映射在 Controller CRUD Spring Boot Rest API 中不起作用

Question

我不知道如何解决api的500状态响应。我正在使用 Postman 进行测试。

请求

{
        "nome": "Ciencia da Computação",
        "totalCreditos": 2333,
        "professor": {
            "id": 2,
            "matricula": 0,
            "nome": "José da silva"
    }
}

如何实现一对多关系并以正确的方式公开 API 以进行 CRUD 操作。我收到 500 错误。我不知道是否需要更改 Controller 功能

CursoController.java

@CrossOrigin(origins = "*")
@RestController
@RequestMapping({"/api/curso"})
public class CursoController {
    @Autowired
    private CursoService cursoService;
    private ProfessorService professorService;

    @PostMapping
    public Curso create(@RequestBody Curso curso){
        return cursoService.create(curso);
    }

    @GetMapping(path = {"/{id}"})
    public Curso findOne(@PathVariable("id") int id){
        return cursoService.findById(id);
    }

    @PutMapping
    public Curso update(@RequestBody Curso Curso){
        return cursoService.update(Curso);
    }

    @DeleteMapping(path ={"/{id}"})
    public Curso delete(@PathVariable("id") int id) {
        return cursoService.delete(id);
    }

    @GetMapping
    public List findAll(){
        return cursoService.findAll();
    }
}

Curso.java

@Entity
@Table(name = "curso")
public class Curso implements Serializable {
    @Id
    @Column
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @Column
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long codigo;
    @Column
    private Long totalCreditos;

    @Column
    private String nome;

    @ManyToOne(fetch = FetchType.LAZY, optional = false, cascade = 
    CascadeType.PERSIST)
    @JoinColumn(name = "professor_id", nullable = false)
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JsonIgnore
    @JsonManagedReference
    private Professor professor;


}

Answer 1

您永远不应该在 @ManyToOne 上使用 CascadeType.ALL，因为实体状态转换应该从父实体传播到子实体。

删除

(fetch = FetchType.LAZY, optional = false, cascade = 
    CascadeType.PERSIST)

来自

@ManyToOne(fetch = FetchType.LAZY, optional = false, cascade = 
    CascadeType.PERSIST)

并将其添加到

 @OneToMany(fetch = FetchType.LAZY, optional = false, cascade = 
        CascadeType.PERSIST)

侧面。

说明:

正如 vladmihalcea 在 this article 中所解释的那样在他的书中，High-Performance Java Persistence ，你不应该使用 CascadeType.ALL上@ManyToOne自 entity state transitions应该从父实体传播到子实体。

@ManyToOne side 始终是 Child 关联，因为它应该映射底层 FK。

因此，移动CascadeType.ALL来自@ManyToOne关联到 @OneToMany应该使用 mappedBy属性，因为它是 the most efficient one-to-many mapping 。`