JPA使用@ManyToMany注解关联实体时出现JSON序列化无限递归错误

我创建了两个映射数据库表的实体类，二者通过标注了@ManyToMany注解的变量建立关联。但我尝试向项目中添加学生时，出现了无限递归错误。

我曾参考多个相关教程和技术社区方案尝试解决，均未生效。

Student类代码如下： #

@Entity
@Table(name = "student")
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {

    @Id
    @GeneratedValue
    @Column(name="student_id")
    private Integer studentId;

    @Column(nullable = false, length = 50)
    private String imie;

    @Column(nullable = false, length = 100)
    private String nazwisko;

    @Column(unique=true, nullable = false, length = 50, name = "nr_indeksu")
    private String nrIndeksu;

    @Column(nullable = false, length = 50)
    private String email;

    @Column(nullable = false)
    private boolean stacjonarny;

    @ManyToMany(mappedBy = "studenci")
    @JsonIgnore
    private Set<Projekt> projekty;

    @Column(nullable = false, length = 50)
    private String haslo;
}

Projekt类代码如下： #

@Entity
@Table(name = "projekt")
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Projekt {

    @Id
    @GeneratedValue
    @Column(name = "projekt_id")
    private Integer projektId;

    @Column(nullable = false, length = 50)
    private String nazwa;

    @Column(nullable = false, length = 1000)
    private String opis;

    @Column(nullable = false, name = "dataczas_utworzenia")
    private LocalDateTime dataczasUtworzenia;

    @Column(nullable = false, name = "data_oddania")
    private LocalDate dataOddania;

    @OneToMany(mappedBy = "projekt")
    @JsonIgnoreProperties(value ={"projekt"}, allowSetters = true)
    private List<Zadanie> zadania;

    @ManyToMany
    @JoinTable(name = "projekt_student",
    joinColumns = {@JoinColumn(name="projekt_id")},
    inverseJoinColumns = {@JoinColumn(name="student_id")})
    private Set<Student> studenci;
    
}

报错日志如下： #

2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Infinite recursion (StackOverflowError); nested exception is com.fasterxml.jackson.databind.JsonMappingException: Infinite recursion (StackOverflowError) (through reference chain: org.springframework.data.domain.PageImpl["content"]->java.util.Collections$UnmodifiableRandomAccessList[7]->com.project.rest.model.Student["projekty"])]
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@f1ff33b<rs=HikariProxyResultSet@922089472 wrapping org.postgresql.jdbc.PgResultSet@57f69f62>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@4110461d<rs=HikariProxyResultSet@1176750721 wrapping org.postgresql.jdbc.PgResultSet@57ac7e31>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@275ad9d4<rs=HikariProxyResultSet@919944575 wrapping org.postgresql.jdbc.PgResultSet@44345fd2>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@7d7d9e7<rs=HikariProxyResultSet@1405186173 wrapping org.postgresql.jdbc.PgResultSet@33be62da>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@42db9900<rs=HikariProxyResultSet@1173506052 wrapping org.postgresql.jdbc.PgResultSet@24f79446>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@1dd679de<rs=HikariProxyResultSet@844941445 wrapping org.postgresql.jdbc.PgResultSet@5d3e700c>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@43b3e132<rs=HikariProxyResultSet@824582406 wrapping org.postgresql.jdbc.PgResultSet@5bfe18a6>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@75c8828e<rs=HikariProxyResultSet@1405429510 wrapping org.postgresql.jdbc.PgResultSet@5b58222b>
2021-08-04 17:26:15.991  WARN 18144 --- [nio-8080-exec-3] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@73ee203<rs=HikariProxyResultSet@1788253192 wrapping org.postgresql.jdbc.PgResultSet@2caee16a>

首先排查最常见的导包错误：你在Student类projekty字段上加的@JsonIgnore如果导入的是org.hibernate.annotations.JsonIgnore，不会对Jackson序列化生效，正确导入包应为com.fasterxml.jackson.annotation.JsonIgnore。

如果确认导包正确仍报错，或你需要在序列化时保留双向关联的字段信息，可使用@JsonIgnoreProperties注解避免循环，具体修改如下：

1. 移除Student类projekty字段上的@JsonIgnore，替换为@JsonIgnoreProperties("studenci")，表示序列化Projekt集合时忽略其内部的studenci字段
2. 给Projekt类的studenci字段加上@JsonIgnoreProperties("projekty")，表示序列化Student集合时忽略其内部的projekty字段

修改后的核心代码片段如下：

Student类关联字段修改 #

@ManyToMany(mappedBy = "studenci")
@JsonIgnoreProperties("studenci")
private Set<Projekt> projekty;

Projekt类关联字段修改 #

@ManyToMany
@JoinTable(name = "projekt_student",
joinColumns = {@JoinColumn(name="projekt_id")},
inverseJoinColumns = {@JoinColumn(name="student_id")})
@JsonIgnoreProperties("projekty")
private Set<Student> studenci;

该方案既不会触发递归序列化，又能在返回Student时携带关联的Projekt列表、返回Projekt时携带关联的Student列表，兼顾业务需求和序列化要求。

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