StackOverflowError: 在双向关系中为 null

huangapple
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英文:

StackOverflowError: null in both side relationship

问题

这是我第一次面临这个问题。我有两个具有相互关系的实体，使用了 @OneToMany 和 @ManyToOne 注解。

团队实体：

@Entity
@Data
public class Team {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String image;

    @OneToMany(cascade = CascadeType.REMOVE, fetch = FetchType.EAGER, mappedBy = "team")
    private List<Player> playerList = new ArrayList<>();
}

球员实体：

@Data
@Entity
public class Player {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String nickname;

    @ManyToOne
    private Team team;
}

我想实现的是，在将球员列表保存到团队后，球员们能够在他们的表中接收到这个团队的记录。在将团队设置给球员后（这样我就知道这个球员在这个团队中），并通过例如以下控制器获取球员列表：

@RestController
@RequestMapping("/api")
@RequiredArgsConstructor
public class PlayerController {
    private final PlayerRepository playerRepository;

    @GetMapping("/player")
    public List<Player> getPlayers() {
        return playerRepository.findAll();
    }
}

我遇到了 java.lang.StackOverflowError: null 错误：

2020-03-15 21:58:48.419  WARN 8576 --- [nio-8080-exec-2] .w.s.m.s.DefaultHandlerExceptionResolver : 在尝试解析异常时失败 [org.springframework.http.converter.HttpMessageNotWritableException]

java.lang.IllegalStateException: 在响应被提交之后无法调用 sendError()
[...]
...

看起来像是陷入了某种循环，但我不知道为什么。对于每一次的帮助，我都会非常感激！

英文:

This is the first time I'm facing this problem. I have two entities with mutual relationships @OneToMany and @ManyToOne.

Team entity:

@Entity
@Data
public class Team {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String image;

    @OneToMany(cascade = CascadeType.REMOVE, fetch = FetchType.EAGER, mappedBy = &quot;team&quot;)
    private List&lt;Player&gt; playerList = new ArrayList&lt;&gt;();
}

Player entity:

@Data
@Entity
public class Player {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String nickname;

    @ManyToOne
    private Team team;
}

I want to achieve that after saving the list of players to the team, players receive the record of this team to their table. After setting team to the player (so I know that this player is in the team) and getting list of players e.g. using this controller:

@RestController
@RequestMapping(&quot;/api&quot;)
@RequiredArgsConstructor
public class PlayerController {
    private final PlayerRepository playerRepository;

    @GetMapping(&quot;/player&quot;)
    public List&lt;Player&gt; getPlayers() {
        return playerRepository.findAll();
    }
}

I'm being faced with java.lang.StackOverflowError: null:

2020-03-15 21:58:48.419  WARN 8576 --- [nio-8080-exec-2] .w.s.m.s.DefaultHandlerExceptionResolver : Failure while trying to resolve exception [org.springframework.http.converter.HttpMessageNotWritableException]

java.lang.IllegalStateException: Cannot call sendError() after the response has been committed
[...]

2020-03-15 21:58:48.423 ERROR 8576 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is 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: com.gottaaimfast.website.model.Player[&quot;team&quot;]-&gt;com.gottaaimfast.website.model.Team[&quot;playerList&quot;]-&gt;org.hibernate.collection.internal.PersistentBag[0]-&gt;com.gottaaimfast.website.model.Player[&quot;team&quot;]-&gt;com.gottaaimfast.website.model.Team[&quot;playerList&quot;]-&gt;org.hibernate.collection.internal.PersistentBag[0]-&gt;com.gottaaimfast.website.model.Player[&quot;team&quot;]-&gt;com.gottaaimfast.website.model.Team[&quot;playerList&quot;]-&gt;org.hibernate.collection.internal.PersistentBag[0]-&gt;com.gottaaimfast.website.model.Player[&quot;team&quot;]-&gt;com.gottaaimfast.website.model.Team[&quot;playerList&quot;]-&gt;org.hibernate.collection.internal.PersistentBag[0]-&gt;com.gottaaimfast.website.model.Player[&quot;team&quot;]-&gt;com.gottaaimfast.website.model.Team[&quot;playerList&quot;]-&gt;org.hibernate.collection.internal.PersistentBag[0]-&gt;[...] with root cause

java.lang.StackOverflowError: null
	at java.base/java.lang.ClassLoader.defineClass1(Native Method) ~[na:na]
	at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016) ~[na:na]
	at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174) ~[na:na]
	at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:800) ~[na:na]
	at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:698) ~[na:na]
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:621) ~[na:na]
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:579) ~[na:na]
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) ~[na:na]
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[na:na]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:737) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:145) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:107) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:145) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:107) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719) ~[jackson-databind-2.9.8.jar:2.9.8]
	at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155) ~[jackson-databind-2.9.8.jar:2.9.8]
**AND IT LOOPS OVER AND OVER**

It seems like it bumps into some kind of loop but I have no idea why. I would be really thankful for every help!

答案1

得分: 2

循环是因为您依赖默认的 JSON 序列化。您拥有双向的多对一关系，因此：

  • 对于每个玩家，您想要输出他所在的团队
  • 对于团队，您输出团队中的玩家

因此，在您的序列化过程中出现了循环。

您的选项是：

  • 在多对一关系的一侧使用 @JsonIgnore 来打破循环
  • 使用自定义的无循环 DTO 来传输数据
  • 使用 @JsonManagedReference 和 @JsonBackReference。
英文:

The loop is due to the fact that you are relying on default serialization to json. You have a bi-directional ManyToOne relationship, so:

  • For each player, you want to output his team
  • For the team, you output the players in the team

and thus yoy have a cycle in your serialization process.

Your options are:

  • use @JsonIgnore on one side of the ManyToOne relationship to break the cycle
  • use a custom DTO With no cycles to transfer the data
  • Use @JsonManagedReferenceand @JsonBackReference

答案2

得分: 2

在Player类中：

@ManyToOne
@JsonManagedReference
private Team team;

在Team类中：

@JsonBackReference
@OneToMany(cascade = CascadeType.REMOVE, fetch = FetchType.EAGER, mappedBy = "team")
private List<Player> playerList = new ArrayList<>();

参考这个答案：

https://stackoverflow.com/questions/60599630/prevent-recursive-association-in-manytoone-hibernate/60600242#60600242

英文:

this bidirectional json mapping problem add these annotations to your entities corresponding fields

In Player:

    @ManyToOne
    @JsonManagedReference
    private Team team;

In Team:

    @JsonBackReference
    @OneToMany(cascade = CascadeType.REMOVE, fetch = FetchType.EAGER, mappedBy =&quot;team&quot;)
    private List&lt;Player&gt; playerList = new ArrayList&lt;&gt;();

See this answer:

https://stackoverflow.com/questions/60599630/prevent-recursive-association-in-manytoone-hibernate/60600242#60600242

huangapple
  • 本文由 发表于 2020年3月16日 05:21:20
  • 转载请务必保留本文链接：https://go.coder-hub.com/60697770.html
  • hibernate
  • java
  • jpa
  • spring
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