SpringJava。util。收藏。交换(列表<?>列表,int i,int j)不执行任何操作
我有一个JavaSpringMVC,我的一个模型是Category
@Entity
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class Category extends AuditModel {
@JsonView(DataTablesOutput.View.class)
String name;
boolean active;
@Column(columnDefinition = "TEXT")
String description;
@Column(length = 70)
String metaTitle;
@Column(length = 160)
String metaDescription;
String friendlyUrl;
@OneToMany
List<Category> secondaryCategories;
String image;
Long position;
}
我尝试用java交换secondaryCategories列表中两个类别的位置。util。收藏。交换(List,inti,intj),但什么都没有发生,也没有错误
@Override
public ResponseEntity moveCategoryUpOrDown(Long id, Long parentId, String direction) {
if (id == parentId) {
return new ResponseEntity<>("Home category cat't be moved",HttpStatus.BAD_REQUEST);
}
Category category = categoryRepository.findOne(id);
Category parent = categoryRepository.findOne(parentId);
List<Category> secondaryCategories = parent.getSecondaryCategories();
if (direction.compareTo("up") == 0) {
if (secondaryCategories.indexOf(category) <= 0)
return new ResponseEntity<>(HttpStatus.OK);
int i = secondaryCategories.indexOf(category);
int j = secondaryCategories.indexOf(category) - 1;
// Category previous = secondaryCategories.get(j);
Collections.swap(secondaryCategories, i, j);
// categoryRepository.saveAndFlush(previous);
// categoryRepository.saveAndFlush(category);
categoryRepository.saveAndFlush(parent);
}
... etc ..
我还尝试了EntityManager在交换之前分离对象,但没有成功。我制定了自己的交换方法,但无法交换
如何在secondaryCategories中交换两个类别
# 1 楼答案
您需要更新它们的
position
字段,或者任何设置实体顺序的字段。从ORM的角度来看,更改集合的顺序毫无意义