由一对多关系引起的hibernate堆栈溢出

Question

我已经创建了一个一对多的关系。虽然当我通过 id 从多到一侧查询对象时一切看起来都很好，但连接的列会抛出一个 Whosebug 异常，我无法弄清楚为什么会发生。大致上我已经关注了this tutorial.

玩家实体

@Entity
@Data
public class Player {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "player_id", updatable = false, unique = true, nullable = false)
    private Long id;
    @Column(name = "name")
    private String name;
    @Column(name = "num")
    private int num;
    @Column(name = "position")
    private String position;
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "team_id")
    private Team team;
}

团队实体

@Entity
@Data
public class Team {
    @Id
    @Column(name="team_id", updatable = false, unique = true)
    private String id;
    @Column(name = "name")
    private String name;
    @OneToMany(mappedBy = "team")
    private List<Player> players;
}

我的播放器库

@Repository
public interface PlayerRepository extends CrudRepository<Player, Long> {
    Optional<Player> findById(Long id);
}

import.sql

中的数据库条目

insert into Team (team_id,name) values('Barcelona','Barcelona');
insert into Player (name,num,position,team_id) values('Andreas Inniesta', 8, 'Midfielder', 'Barcelona');
insert into Player (name,num,position,team_id) values('Lionel Messi', 10, 'Forward', 'Barcelona');

玩家 table 在 h2-console

这是例外情况

java.lang.WhosebugError: null
        at java.lang.StringBuilder.append(StringBuilder.java:136) ~[na:1.8.0_121]
        at mypackage.entity.Player.toString(Player.java:8) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at java.util.AbstractCollection.toString(AbstractCollection.java:462) ~[na:1.8.0_121]
        at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:510) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Team.toString(Team.java:9) ~[classes!/:1.0-SNAPSHOT]
        at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source) ~[na:na]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
        at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:84) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at mypackage.entity.Team_$$_jvst2b7_1.toString(Team_$$_jvst2b7_1.java) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Player.toString(Player.java:8) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at java.util.AbstractCollection.toString(AbstractCollection.java:462) ~[na:1.8.0_121]
        at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:510) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Team.toString(Team.java:9) ~[classes!/:1.0-SNAPSHOT]
        at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source) ~[na:na]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
        at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:84) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at mypackage.entity.Team_$$_jvst2b7_1.toString(Team_$$_jvst2b7_1.java) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Player.toString(Player.java:8) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at java.util.AbstractCollection.toString(AbstractCollection.java:462) ~[na:1.8.0_121]
        at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:510) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Team.toString(Team.java:9) ~[classes!/:1.0-SNAPSHOT]
        at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source) ~[na:na]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
        at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:84) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at mypackage.entity.Team_$$_jvst2b7_1.toString(Team_$$_jvst2b7_1.java) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Player.toString(Player.java:8) ~[classes!/:1.0-SNAPSHOT]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at java.util.AbstractCollection.toString(AbstractCollection.java:462) ~[na:1.8.0_121]
        at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:510) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
        at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
        at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
        at mypackage.entity.Team.toString(Team.java:9) ~[classes!/:1.0-SNAPSHOT]
        at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source) ~[na:na]

异常的根源

at mypackage.entity.Team.toString(Team.java:9) ~[classes!/:1.0-SNAPSHOT]
at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source) ~[na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:84) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
at mypackage.entity.Team_$$_jvst2b7_1.toString(Team_$$_jvst2b7_1.java) ~[classes!/:1.0-SNAPSHOT]
at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
at mypackage.entity.Player.toString(Player.java:8) ~[classes!/:1.0-SNAPSHOT]
at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
at java.util.AbstractCollection.toString(AbstractCollection.java:462) ~[na:1.8.0_121]
at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:510) ~[hibernate-core-5.2.17.Final.jar!/:5.2.17.Final]
at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_121]
at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_121]
at mypackage.entity.Team.toString(Team.java:9) ~[classes!/:1.0-SNAPSHOT]
at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source) ~[na:na]

进一步调试错误表明，在连接列上某种类型的字符串内部转换失败。

Answer 1

发生这种情况是因为当你想查询团队时，比如团队 'A'，它还包含团队 'A' 中的球员列表，这些列表本身包含他们所在的团队(team 'A')，它还带有一个 Players 列表......你明白了，它在这种关系中无限循环，没有尽头。为避免 Whosebug 错误，如果使用 Jackson，则需要使用 @JsonIgnore 注释 @OneToMany 的一侧，如果使用普通 jsonb，则需要使用 @JsonbTransient 注释。

@OneToMany(mappedBy = "team")
@JsonIgnore
private List<Player> players;

或

@OneToMany(mappedBy = "team")
@JsonbTransient
private List<Player> players;

这样，在查询球队时，球员名单将被忽略，您将避免错误。

Answer 2

据我所知，您正在使用 Lombok。

您认为您没有创建 toString 方法，但 Lombok 不这么认为。 @Data 注释导致生成 toString 方法。

来自 Lombok 文档：

@Data is a convenient shortcut annotation that bundles the features of @ToString, @EqualsAndHashCode, @Getter / @Setter and @RequiredArgsConstructor together: In other words, @Data generates all the boilerplate that is normally associated with simple POJOs (Plain Old Java Objects) and beans: getters for all fields, setters for all non-final fields, and appropriate toString, equals and hashCode implementations that involve the fields of the class, and a constructor that initializes all final fields, as well as all non-final fields with no initializer that have been marked with @NonNull, in order to ensure the field is never null.

因此 Lombok 为您创建了 toString 导致无限递归的方法。

您可以通过以下方式修复它：

@Data
@ToString(exclude = "players")
public class Team {
   // ...
}

或者：

@Data
public class Team {
    @OneToMany(mappedBy = "team")
    @ToString.Exclude
    private List<Player> players;
}

值得一提的是，如果您仍然需要在 Team 的 toString 表示中包含 players，请尝试反汇编 @Data 注释并仅添加部分你真的需要。然后定义你自己的toString方法。

Answer 3

即使我也遇到过类似的问题。我在尝试保持一对多关系时遇到 Whosebug 错误。解决方案是。

@Data
@EqualsAndHashCode(exclude = "players")   // players is @OneToMany
 class Team {
  @OneToMany(mappedBy = "team")
   private List<Player> players;
 }

这是导致问题的原因，因为它曾经使用所有实体创建哈希码。这导致递归。

由一对多关系引起的hibernate堆栈溢出

Stack overflow on hibernate caused by one to many relationship

java

hibernate

lombok

spring-boot