避免对休眠的循环依赖

Question

package com.example.demo.model;

import com.sun.istack.NotNull;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;

import javax.persistence.*;
import java.util.*;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
@EntityListeners(AuditingEntityListener.class)
@Table(name="MEDICAL_DEVICE")
public class MedicalDevice {

    public MedicalDevice(UUID deviceId, DefectPriority defectPriority, State currentState) {
        this.deviceId = deviceId;
        this.defectPriority = defectPriority;
        this.currentState = currentState;
    }

    public MedicalDevice(UUID deviceId, State currentState) {
        this.deviceId = deviceId;
        this.currentState = currentState;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @Column(name="DEVICE_ID")
    @NotNull
    private UUID deviceId;

    @Column(name="DEFECT_PRIORITY", nullable = true)
    @Enumerated(EnumType.STRING)
    private DefectPriority defectPriority;

    @OneToMany(mappedBy="medicalDevice")
    private List<State> states = new ArrayList<>();

    @OneToOne(mappedBy="medicalDevice")
    private State currentState;



}


package com.example.demo.model;

import com.sun.istack.NotNull;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.NonNull;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;

import javax.persistence.*;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.util.List;
import java.util.UUID;

@Data
@NoArgsConstructor
@AllArgsConstructor
@Entity
@EntityListeners(AuditingEntityListener.class)
@Table(name="STATE")
public class State {

    public State(StateNames state, UUID enteredBy, LocalDateTime enteredAt) {
        this.state = state;
        this.enteredBy = enteredBy;
        this.enteredAt = enteredAt;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

    @Enumerated(EnumType.STRING)
    private StateNames state;

    @Column(name="USER_ID")
    private UUID enteredBy;       //User who changed the devices state to this one

    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="MEDICAL_DEVICE_ID")
    @NotNull
    private MedicalDevice medicalDevice;



    @Column(name = "LOCAL_DATE_TIME", columnDefinition = "TIMESTAMP")
    private LocalDateTime enteredAt;    //Time when the devices state was changed into this one

    @Column(name = "LOCAL_DATE", columnDefinition = "DATE")
    private LocalDate availabilityDate; //Date when a device will be available (only used in defect states and bought state)

    @OneToMany(mappedBy="state")
    private List<AdditionalInformation> additionalInformation;


}

如何避免 State class 和 MedicalDevice class 之间对休眠的循环依赖？我已经实现了@OneToMany List，它是旧状态，@OneToOne State currentState 指示当前状态。我想让它在列表中不是全部分开，但我的实现导致> enter image description here

Answer 1

您没有提供错误消息，因此很难确切知道是什么导致了循环依赖，但基本思想是它源于 MedicalDevice 引用了 State 反之亦然，所以相互依赖。

（顺便说一句，您还设置了 MedicalDevice 以拥有一个具有 @OneToMany 关系的 State 列表，以及一个具有 @OneToOne 关系的 State 实例。那并没有真正起作用，要么是@OneToMany，要么是@OneToOne。换句话说，要么 MedicalDevice 有一个 State，要么有很多 State，但它没有两者都有。我不知道这是否会导致您的问题）。

无论如何，循环依赖可能是由于调用了 equals/hashcode 或 toString 方法。 MedicalDevice 可能会在其 State 变量上调用这些方法，而后者又会在其 MedicalDevice 变量上调用这些方法，等等

一种可能的解决方法是从 equals/hashcode 和 toString 方法中排除引用。但同样，如果没有错误的详细信息，很难说出确切的问题是什么。

Answer 2

使用 @JsonIgnore 注释在您的州 class 内注释 MedicalAdvice 对象。这样，您可以防止从实体 classes.

之间的关系中无限递归获取数据

避免对休眠的循环依赖

avoid circular dependency on hibernate

java

spring

hibernate

spring-data

spring-data-jpa