那些遇到过的问题

hibernate上的堆栈溢出由一对多关系引起

Dim*_*ris 1 java hibernate lombok spring-boot

我创造了一对多的关系.虽然当我通过id从多边到一边查询对象时,一切似乎都很好,但是连接列抛出了一个stackoverflow异常,我无法弄清楚它为什么会发生.我大概遵循了本教程.

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;
}
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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;
}
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我的播放器库

@Repository
public interface PlayerRepository extends CrudRepository<Player, Long> {
    Optional<Player> findById(Long id);
}
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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');
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h2-console上的播放器表 在此输入图像描述

这是个例外

java.lang.StackOverflowError: 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]
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异常的根

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]
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此外,调试错误表明某些内部转换为字符串在连接列上失败. 在此输入图像描述

J-A*_*lex 6

我可以看到你正在使用Lombok.

你认为你不是在创造toString方法,但Lombok并不这么认为.该@Data注释将使得生成的toString方法.

来自Lombok文档:

@Data是一个方便的快捷方式注释,它捆绑了@ToString,@EqualsAndHashCode和@Getter/ @Setter和 的特征 @RequiredArgsConstructor:换句话说,@Data生成通常与简单POJO(普通旧Java对象)和bean相关联的所有样板:所有字段的getter,所有非的setter最后的字段,以及适当的toString,equals和hashCode实现,它们涉及类的字段,以及初始化所有final字段的构造函数,以及所有没有标记的初始化程序的非final字段, @NonNull以确保字段永远不会为空.

所以为你Lombok创建的toString方法导致无限递归.

您可以通过以下方式修复:

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

@Data
public class Team {
    @OneToMany(mappedBy = "team")
    @ToString.Exclude
    private List<Player> players;
}
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值得一提的,如果你还需要包括players在Team的toString表现,试图拆卸@Data注释,并添加只有你真正需要的部分.然后定义自己的toString方法.

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