在没有@JsonIgnore的情况下使用休息服务后出现错误

Question

我有此映射用户* ----------- 1 Sexe

User.class

public class User {
    @ManyToOne
    @JoinColumn(name="sexe_id")
    private Sexe sexe;

   // Rest of the Attributes
}

Sexe.class

public class Sexe {    
    @OneToMany(mappedBy="sexe", fetch = FetchType.LAZY)
    private List<User> users;

   // Rest of the Attributes

}

和休息呼叫控制器

@GetMapping("/users")
public List<User> getAllUsers()
{
     System.out.println("Get all Users...");
     List<User> users = new ArrayList<>();
     userRepository.findAll().forEach(users::add);
     return users;
}

使用邮递员后，出现此异常：

 at
 com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:145)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:107)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at
 com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
 ~[jackson-databind-2.9.6.jar:2.9.6]    at

在谷歌搜索之后，我发现解决方案是使用@JsonIgnore。 这个注释解决了我的问题。但是，使用此注释会导致角度问题。

请您提出其他建议以避免这种例外情况？非常感谢您的帮助。

Answer 1

JsonIgnore不是唯一的解决方案。您还可以使用@JsonManagedReference和@JsonBackReference

@ManyToOne
@JsonBackReference
@JoinColumn(name="sexe_id")
private Sexe sexe;

@JsonManagedReference
@OneToMany(mappedBy="sexe", fetch = FetchType.LAZY)
private List<User> users;

请参见Could not write JSON: Infinite recursion (StackOverflowError); nested exception spring boot