OneToMany 和 ManyToOne 实体 objects 在递归中链接

Question

在我的 java-spring 引导应用程序中，我遇到了 2 java class 与注释 @oneToMany 和 @ManyToOne 的 parent-children 双向关系的问题。

当我尝试将它们保存在数据库中并向控制器端点发送 post 请求时，会在两个 object 之间创建一个递归循环。在controller中调用@getMapping(/{fatherId})方法也出现同样的问题

基本上 java 收到父亲 object 包含一组 Children 引用他们的父亲 object ，其中包含他们的 children榜等等等等..

我该如何解决这个问题？我看到一些类似的 post 建议使用 Jackson 库注释，是否绝对有必要将它添加到 pom 中？我更喜欢在我的 pom 中引用基本的最小包集，而 Jackson 还没有在使用 Spring Initializer(spring boot).

编写的默认包中

谢谢大家的建议！

parentclass是父亲:

@Entity
 @Table(name="Father")
 public class Father {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;

private String name;

@OneToMany(mappedBy="father", fetch = FetchType.LAZY)
private Set<Child> children;

一个父亲可以有多个child人，但一个child只能有一个父亲。

childclass:

@Entity
@Table(name="Child")
public class Child {

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;

private String name;

@ManyToOne
@JoinColumn(name ="ID_FATHER")
private Father father;

控制器中的端点是这样的：

@Transactional
@PostFather(path = "/newFather", consumes = "application/json", produces = "application/json")
public ResponseEntity<?> createNewFather(@Valid @RequestBody Father father, BindingResult result) {



    Set<Child> childrenSet = new HashSet<Child>();
    //ArrayList<Child> newChildren= new ArrayList<Child>();
    //newChildren.addAll(father.getChildren());
    for (Child c : father.getChildren()) {
        Child newChild = new Child();
        newChild.setId(c.getId());
        newChild.setName(c.getName());
        newChild.setFather(father);

        fatherService.saveOrUpdateChild(newChild);
        childrenSet.add(newChild);
    }
    father.setChildren(childrenSet);
    Father newFather = fatherService.saveOrUpdateFather(father);


    return new ResponseEntity<Father>(newFather, HttpStatus.CREATED);
}

@GetFather("/father/{fatherId}")
public ResponseEntity<?> getFatherById(@PathVariable int fatherId) {

    Father father = fatherService.findFatherById(fatherId);
    for (Child c : father.getChildren()) {// !!workaround to stop the loop!!
        c.setFather(null);
    }
    return ResponseEntity.ok().body(father);

}

问题是当我发送到

http://localhost:8080/api/myapi/newFather

Jsonpost请求：

{
"name": "new father test 12",
"Children": [
    {
        "name": "Child test 12_1",
    },
    {
        "name": "Child test 12_2",
    },
 ]
}

我得到一个循环作为响应：

{
   "id":197,
   "name":"father test 12",
   "children":[
      {
         "id":196,
         "name":"row test 12_1",
         "father":{
        "id":197,
        "name":"father test 12",
        "children":[
           {
              "id":196,
              "name":"row test 12_1",
              "father":{   /* ENDLESS LOOP !*/
           }
        ]
     }
  ]
  ]

Answer 1

只需在Child的Father属性中添加@JsonIgnore注解即可class

@ManyToOne
@JoinColumn(name ="ID_FATHER")
@JsonIgnore
private Father father;

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