Question

我遇到了通过Spring Data Rest将@RelationshipEntities序列化为JSON的问题。每当我创建@RelationshipEntity时，我都会在将图形序列化为JSON时遇到无限递归。

使用JSOG尝试渲染图形只会导致不同的，错误的JSON响应。

虽然我可以通过使用@JsonManagedReference来避免这个问题，但它并没有解决问题，因为我想从两个节点公开关系。

我创建了一个展示问题的简单应用程序。可在此处找到：https://github.com/cyclomaniac/neo4j-spring-data-rest-cyclic

它使用单个RelationshipEntity，PlayerPosition实现非常基本的Team和Player NodeEntities。

播放器：

@NodeEntity
@JsonIdentityInfo(generator= JSOGGenerator.class)
public class Player {

    @GraphId
    @JsonProperty("id")
    private Long id;
    private String name;
    private String number;

    @Relationship(type = "PLAYS_ON")
    private PlayerPosition position;

    ...

小组：

@NodeEntity
@JsonIdentityInfo(generator= JSOGGenerator.class)
public class Team {

    @GraphId
    @JsonProperty("id")
    private Long id;
    private String name;

    @Relationship(type = "PLAYS_ON", direction = Relationship.INCOMING)
    Set<PlayerPosition> teamPlayers;

    ...

PlayerPosition：

@RelationshipEntity(type="PLAYS_ON")
@JsonIdentityInfo(generator= JSOGGenerator.class)
public class PlayerPosition {
    @GraphId
    @JsonProperty("id")
    private Long id;
    private String position;

    @StartNode
    private Player player;


   @EndNode
   private Team team;

   ...

当连接到GraphRepository时，点击/ teams端点会产生以下输出，并带有JSOG：

{
  "_embedded" : {
    "teams" : [ {
      "@id" : "1",
      "name" : "Cubs",
      "teamPlayers" : [ {
      "@id" : "2",
        "position" : "Catcher",
        "player" : {
          "@id" : "3"

请注意，JSON过早结束。服务器抛出异常：

2016-11-04 15:48:03.495  WARN 12287 --- [nio-8080-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to write HTTP message:
 org.springframework.http.converter.HttpMessageNotWritableException: 
 Could not write content: Can not start an object, 
 expecting field name; nested exception is 
 com.fasterxml.jackson.core.JsonGenerationException: 
 Can not start an object, expecting field name

我的假设是，我选择了一种糟糕的方式来实现这种关系，尽管感觉相当简单。我非常感谢有关如何通过Spring Data Rest从Team和Player节点正确展示这种关系的任何提示。

Answer 1

尝试使用@JsonIgnore注释或配对：@JsonBackReference和@JsonManagedReference

Spring Data Rest的Neo4j RelationshipEntities和循环JSON序列化问题

1 个答案: