Spring Boot中Team与Match关联JSON循环引用问题及解决

最近碰到一个挺典型的JPA+Jackson序列化坑：我的系统里Team（队伍）和Match（对战比赛）是双向关联的——Team有自己参与的matches集合，Match里又包含对战的两个Team（teamHome和teamAway）。查询Team的时候要展示它参与的所有Match，但直接序列化会陷入无限嵌套：返回的Match里有两个Team，每个Team又带着自己的matches数组，循环往复根本停不下来。

最开始我想着用@JsonBackReference注解，直接加在Team类的matches集合上，结果倒好，整个matches数组直接被隐藏了，完全不符合我要展示Team参与赛事的需求。我的目标很明确：展示Team的matches数组，但每个Match里的teamHome和teamAway不能再带它们自己的matches集合。

我的实体类关联关系 #

先贴一下当时的实体类代码，方便大家理解场景：

Match类（初始版本）

@Entity @Getter @Setter @Table(name="match")
public class Match {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @ManyToOne @JoinColumn(name = "team_id_home")
    private Team teamHome;
    @ManyToOne @JoinColumn(name = "team_id_away")
    private Team teamAway;
    private int scoreTeamHome;
    private int scoreTeamAway;
    private int nrOfWinsNeeded;
    @Temporal(TemporalType.TIMESTAMP)
    @JsonFormat(pattern="yyyy-MM-dd HH:mm")
    private Date date;
    public Match() { }
    public Match(Team teamHome, Team teamAway, int scoreTeamHome, int scoreTeamAway, int nrOfWinsNeeded, Date date){
        this.teamHome = teamHome;
        this.teamAway = teamAway;
        this.scoreTeamHome = scoreTeamHome;
        this.scoreTeamAway = scoreTeamAway;
        this.nrOfWinsNeeded = nrOfWinsNeeded;
        this.date = date;
    }
}

Team类（初始版本）

@Entity @Getter @Setter @Table(name = "`team`")
public class Team {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @Column(nullable = false) private String name;
    @Column(nullable = false) private String country;
    @Column(nullable = false, name = "code_name") private String codeName;
    @JsonBackReference
    @OneToMany(cascade = CascadeType.ALL) @JoinColumn(name = "team_id")
    private Set<Match> matches;
    @JsonBackReference
    @OneToMany(mappedBy = "team")
    private Set<Player> players;
    public Team(){ }
    public Team(String name, String country, String codeName) {
        this.name = name;
        this.country = country;
        this.codeName = codeName;
    }
}

最终解决办法 #

试了几种方式之后，发现用@JsonIgnoreProperties注解最贴合我的需求：在Match类的teamHome和teamAway字段上，添加@JsonIgnoreProperties({"matches"})，明确告诉Jackson序列化这两个Team对象时，忽略它们的matches集合。

修改后的Match类关键部分：

@ManyToOne @JoinColumn(name = "team_id_home")
@JsonIgnoreProperties({"matches"})
private Team teamHome;
@ManyToOne @JoinColumn(name = "team_id_away")
@JsonIgnoreProperties({"matches"})
private Team teamAway;

这样处理之后，查询Team返回的JSON里，会正常展示该Team的所有Match数组；而每个Match里的teamHome和teamAway只会包含队伍的基本信息（id、name、country这些），不会再带出它们的matches集合，完美打破了循环引用，同时也满足了业务展示需求。

内容的提问来源于stack exchange，提问作者Appel Taart