春季启动/ JPA：设置并保留父ID

Question

我创建了一个名为category的实体。

package com.app.ws.io.entity;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name="categories")
@Getter @Setter
public class CategoryEntity {
    @Getter(AccessLevel.NONE)
    @Setter(AccessLevel.NONE)
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Long id;

    @Column(length = 30, nullable = false)
    private String categoryKeyId;

    @Column(nullable = false)
    private String name;

    @ManyToOne(optional = true, fetch = FetchType.LAZY)
    private CategoryEntity parentCategory;

    // allow to delete also subcategories
    @OneToMany(mappedBy="parentCategory", cascade = CascadeType.ALL)
    private List<CategoryEntity> subCategories;

}

生成的表包含预期的4个字段。字段parent_id引用数据库的现有ID。

id = 1 name =“ mainCategory” parent_id = null id = 2 name =“ subCategory” parent_id = 1

我使用rest API来为此保存数据，我创建了请求和响应模型

我发送的JSON正在使用此模型：

@Getter @Setter
public class CategoryRequestModel {
    private String name;
    private String parentCategoryKeyId;
}

作为回报，我使用第二种模型：

@Getter @Setter
public class CategoryRest {
    private String categoryKeyId;
    private String name;
}

我的控制器中有一个方法：

@PostMapping(
        consumes = { MediaType.APPLICATION_XML_VALUE, MediaType.APPLICATION_JSON_VALUE },
        produces = { MediaType.APPLICATION_XML_VALUE, MediaType.APPLICATION_JSON_VALUE }
)
public CategoryRest createCategory(@RequestBody CategoryRequestModel categoryRequestModel) throws Exception {
    CategoryRest returnValue = new CategoryRest();

    if( categoryRequestModel.getName().isEmpty())
        throw new NullPointerException(ErrorMessages.MISSING_REQUIRED_FIELDS.getErrorMessage());

    ModelMapper modelMapper = new ModelMapper();
    CategoryDto categoryDto = modelMapper.map(categoryRequestModel, CategoryDto.class);

    CategoryDto createdCategory = categoryService.createCategory(categoryDto);
    System.out.println(createdCategory);
    returnValue = modelMapper.map(createdCategory, CategoryRest.class);

    return returnValue;
}

我在这里将DTO层称为服务层：

@Getter @Setter
public class CategoryDto implements Serializable {
    @Getter(AccessLevel.NONE)
    @Setter(AccessLevel.NONE)
    private static final long serialVersionUID = 1L;

    private long id;
    private Integer parentCategoryId;
    private String name;
    private String categoryKeyId;
    private String parentCategoryKeyId;

    private List<CategoryDto> subCategories;
    private CategoryDto parentCategory;

}

我的服务：

@Override
public CategoryDto createCategory(CategoryDto categoryDto) {
    // check if category exists
    if (categoryRepository.findByName(categoryDto.getName()) != null)
        throw new ApplicationServiceException("Record already in Database");

    ModelMapper modelMapper = new ModelMapper();
    CategoryEntity categoryEntity = modelMapper.map(categoryDto, CategoryEntity.class);

    // generate categoryKeyId
    String categoryKeyId = utils.generateCategoryKeyId(30);
    categoryEntity.setCategoryKeyId(categoryKeyId);
    System.out.println(categoryDto);
    System.out.println("# " + categoryDto.getCategoryKeyId());
    // int can't be null - Integer is nullable
    if (categoryDto.getParentCategoryId() != null) {
        CategoryEntity parentCategory = categoryRepository.findByCategoryKeyId(categoryDto.getCategoryKeyId());
        categoryEntity.setParentCategory(parentCategory);
        System.out.println(categoryEntity);
    }

    CategoryEntity storedCategory = categoryRepository.save(categoryEntity);
    CategoryDto returnValue = modelMapper.map(storedCategory, CategoryDto.class);

    return returnValue;
}

我的问题是我可以保存类别，但是无法在数据库中设置父类别。 如果我通过此Json发送发帖请求：

{
  "name": "sub",
  "parentCategoryId": "6jWswxKNADi9iDPNvs00r7mCd0BxH0"
}

我确实将“ sub”值保存在数据库中，但我根本没有设置parent_id。