ManyToMany关系导致StackOverFlow错误

时间：2019-04-24 20:35:32

标签： hibernate spring-boot orm spring-data-jpa

我有一个名为User的实体，它具有一组角色。我还有一个Role实体，该实体具有一组用户。（这只是出于学习目的的练习应用程序。）

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）发送用户列表-导致StackOverFlow错误。用户尝试加载角色，而角色又依次尝试加载用户等。

我的问题是-如何避免这种情况？我也看到许多类似的设计。例如：https://viralpatel.net/blogs/hibernate-many-to-many-annotation-mapping-tutorial/

为什么他们没有遇到这样的问题？

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]

2 个答案:

答案 0 :(得分：1)

我想在json序列化过程中有一个循环引用。 因此，您需要使用@JsonIgnore批注从序列化过程中排除两个字段之一。

在此处查看先前的答复：https://stackoverflow.com/a/39985263/2311723

答案 1 :(得分：0)

或者，您可以将实体转换为DTO（数据传输对象），然后返回DTO。我建议不要直接退回实体

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