ManyToMany 关系导致 StackOverFlow 错误 [英] ManyToMany relationship leads to StackOverFlow error

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本文介绍了ManyToMany 关系导致 StackOverFlow 错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有一个名为 User 的实体，它具有一组角色.我还有一个角色实体，它有一组用户.(这只是一个用于学习目的的练习应用程序.)

I have an entity called User which has set of roles. I also have a Role entity which has set of users.( This is just a practice application for learning purposes.)

public class User {

    private String firstName;
    private String lastName;

    @ManyToMany
    @JoinTable(name="user_role", 
            joinColumns={@JoinColumn(name="user_id")}, 
            inverseJoinColumns={@JoinColumn(name="role_id")})
    private Set<Role> roles;

    //getters setters

}


public class Role {

    private String name;

    @ManyToMany(mappedBy="roles")
    private Set<Users> users;

    //getters setters

}


Table: User      (id, firstname, lastname....)
Table: Role      (id, name)
Table: User_Role (id, user_id, role_id)

问题是 - 我有一个 UserController (REST API) 来发送用户列表 - 它会导致 StackOverFlow 错误.用户尝试加载角色，角色又尝试加载用户等.

The problem is - I have an UserController (REST API) to send the user list - it leads to StackOverFlow error. User tries to load role which in turn tries to load user etc.

我的问题是 - 如何避免这种情况?我也看到很多类似的设计.例如:https://viralpatel.net/blogs/休眠多对多注解映射教程/

My question is - how to avoid this? I also see many similar designs. For ex: https://viralpatel.net/blogs/hibernate-many-to-many-annotation-mapping-tutorial/

他们怎么没有遇到过这样的问题?

How come they have not come across such issues?

java.lang.StackOverflowError: null
    at java.lang.ClassLoader.defineClass1(Native Method) ~[na:1.8.0_191]
    at java.lang.ClassLoader.defineClass(ClassLoader.java:763) ~[na:1.8.0_191]
    at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142) ~[na:1.8.0_191]
    at java.net.URLClassLoader.defineClass(URLClassLoader.java:468) ~[na:1.8.0_191]
    at java.net.URLClassLoader.access$100(URLClassLoader.java:74) ~[na:1.8.0_191]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:369) ~[na:1.8.0_191]
    at java.net.URLClassLoader$1.run(URLClassLoader.java:363) ~[na:1.8.0_191]
    at java.security.AccessController.doPrivileged(Native Method) ~[na:1.8.0_191]
    at java.net.URLClassLoader.findClass(URLClassLoader.java:362) ~[na:1.8.0_191]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[na:1.8.0_191]
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[na:1.8.0_191]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[na:1.8.0_191]
    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.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.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.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.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.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]

推荐答案

我认为在 json 序列化过程中存在循环引用.因此，您需要使用 @JsonIgnore 注释从序列化过程中排除两个字段之一.

I would suppose that there is a cyclic reference during the json serialization. So you need to exclude one of the two fields from the serialization process by using the @JsonIgnore annotation.

在此处查看之前的回复:https://stackoverflow.com/a/39985263/2311723

See previous response here: https://stackoverflow.com/a/39985263/2311723

这篇关于ManyToMany 关系导致 StackOverFlow 错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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