Spring Data Rest - 发布请求因空指针外键异常而失败

Question

我有一个 Spring Data rest API，我试图在名为 comment 的实体中保存一条新记录。 该实体与另一个名为 department 的实体存在多对一关系。

当我调用此实体的 post api 时，出现空指针错误，但我将部门外键作为邮递员请求的一部分传递。我不确定为什么服务器端没有收到它。有人可以对它有所了解吗？

错误

   "cause": {
        "cause": {
            "cause": null,
            "message": "ERROR: null value in column \"department_id\" of relation \"comments\" violates not-null constraint\n  Detail: Failing row contains (32, null, null, null, null, null)."
        },
        "message": "could not execute statement"
}

评论实体（删除了用于保存行的getter和setter

@Table(name="comments")
public class Comment implements Serializable {
    private static final long serialVersionUID = 1L;

    
    @Id
    @SequenceGenerator(name="SEQUENCE_FOR_COMMENTS", sequenceName="SEQUENCE_FOR_COMMENTS",allocationSize = 1 )
    @GeneratedValue(strategy=GenerationType.AUTO, generator="SEQUENCE_FOR_COMMENTS")
    @Column(name="comment_id")
    private Integer commentId;

    private String comment;

    @ManyToOne
    @JoinColumn(name="department_id")
    private Department department;


}

部门实体（删除了用于保存行的getter和setter

public class Department implements Serializable { private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy=GenerationType.AUTO, generator="SEQUENCE_FOR_Department" )
@Column(name="department_id")
private Long departmentId;

}

邮递员请求

{
"departmentv1":{
    "departmentId":163
},
"comment":"Apr292023"

}

Answer 1

好吧，我认为您首先没有传递 referencedColumnName 它的作用是它表示当前表中关联表（部门）和当前表（评论）之间的关系当前实体是 commentId，它基本上是一个外键和一个关联表（部门）你有你的主键丢失了，但我认为如果你忘记提及它，如果他们都有相同的名字，它不会影响这么大

//实体层

//例如这里是一个示例关联表（类别）

@Table(name = "categories")
public class Categories 
{
@Id
@Column(name = "cat_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@NotBlank
@Column(name = "cat_name")
private String catName;
}

//这是当前表（子类别）

@Table(name = "subcategories")
public class SubCategories 
{
@Id
@Column(name = "sub_cat_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@NotBlank
@Column(name = "sub_cat_name")
private String subCatName;

//it denotes the relationship between current entity(name = "cat_id") in 
present table(Sub_category) with the  referencedColumnName = "cat_id"
present in associated table(Categories)
@JoinColumn(name = "cat_id", referencedColumnName = "cat_id") 
@ManyToOne(fetch = FetchType.LAZY)
private Categories categories;
}

//存储层

//类别

public interface CategoriesRepository extends JpaRepository<Categories, 
Long>
{

}

//子类别

public interface SubCategoriesRepository extends 
JpaRepository<SubCategories, Long>
{

}

//服务层逻辑

public ResponseEntity<Map<String, Object>> 
addSubCategory(AddSubCategoryRequest addSubCategoryRequest)
{
    SubCategories newSubCategoryCategories = new SubCategories();
    newSubCategoryCategories.setSubCatName(addSubCategoryRequest.
                                           getSubCatName());
 
    newSubCategoryCategories.setCategories(addSubCategoryRequest.
                                           getCategories());
    Map<String, Object> map = new LinkedHashMap<>();
    map.put("data", 
            subCategoriesRepository.save(newSubCategoryCategories));
    map.put(sts, true);
    map.put(msg, "Sub-Category added success");
    return ResponseEntity.ok().body(map);
}

//控制器层

@PostMapping("/admin/add/sub/category")
public ResponseEntity<Map<String, Object>> addSubCategory(@RequestBody 
@Valid AddSubCategoryRequest subCategory)
{
    return service.addSubCategory(subCategory);
}

//邮差请求

{
"subCatName":"T-shirts",
"categories":{
    "id":1,
    "catName":"Clothing and fashion"
}
}

我在这里还可以看到一件事，您只是传递 departmentId 而不是 department 表的其他值希望这个例子能解决您的问题，如果没有，请告诉我

Answer 2

看起来问题出在您在 Postman 请求中发送的 JSON 负载上。您在有效负载中有一个名为“departmentv1”的键，但您的 Comment 实体需要一个名为“department”的键。

更新您的 Postman 请求以匹配预期格式：

{
  "department": {
    "departmentId": 163
  },
  "comment": "Apr292023"
}

这应该可以解决问题，服务器端应该可以正确接收部门外键。