java - 为什么无限循环在加载数据时 hibernate

Question

我尝试加载 storebyid 但在删除时显示错误

@ManyToMany(mappedBy = "stores")
private Set<Product> products;

我可以加载storebyid。

循环 hibernate :

Hibernate: select store0_.store_id as store_id1_6_0_, store0_.status as status2_6_0_, store0_.storename as storenam3_6_0_ from store store0_ where store0_.store_id=?
Hibernate: select products0_.store_id as store_id2_4_0_, products0_.product_id as product_1_4_0_, product1_.product_id as product_1_3_1_, product1_.price as price2_3_1_, product1_.productname as productn3_3_1_ from product_store products0_ inner join product product1_ on products0_.product_id=product1_.product_id where products0_.store_id=?
2562-07-05 16:02:01.197  WARN 15200 --- [nio-8080-exec-9] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to write HTTP message: 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.gpch.hotel.model.Store["products"])
2562-07-05 16:02:01.198  WARN 15200 --- [nio-8080-exec-9] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved exception caused by Handler execution: 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.gpch.hotel.model.Store["products"])
2562-07-05 16:02:01.198  WARN 15200 --- [nio-8080-exec-9] o.h.e.loading.internal.LoadContexts      : HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@876165<rs=HikariProxyResultSet@11556352 wrapping com.mysql.jdbc.JDBC42ResultSet@1095230>

package com.gpch.hotel.model;

import lombok.Data;

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

@Data
@Entity
@Table(name = "store")
public class Store {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "store_id")
    private int id;
    @Column(name = "storename")
    private String storeName;
    @Column(name = "status")
    private String status;
    @ManyToMany(mappedBy = "stores")
    private Set<Product> products;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getStoreName() {
        return storeName;
    }

    public void setStoreName(String storeName) {
        this.storeName = storeName;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public Set<Product> getProducts() {
        return products;
    }

    public void setProducts(Set<Product> products) {
        this.products = products;
    }
}

package com.gpch.hotel.model;

import lombok.Data;

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

@Data
@Entity
@Table(name = "product")
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "product_id")
    private int id;
    @Column(name = "productname")
    private String productname;
    @Column(name = "price")
    private int price;
    @ManyToMany(fetch = FetchType.LAZY, cascade = {CascadeType.ALL})
    @JoinTable(name = "product_store", joinColumns = @JoinColumn(name = "product_id"), inverseJoinColumns = @JoinColumn(name = "store_id"))
    private Set<Store> stores;
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getProductname() {
        return productname;
    }

    public void setProductname(String productname) {
        this.productname = productname;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }

    public Set<Store> getStores() {
        return stores;
    }

    public void setStores(Set<Store> stores) {
        this.stores = stores;
    }
}

Answer 1

我认为这可能与延迟加载的集合有关 - 默认情况下，@ManyToMany 注释获取类型是 FetchType.LAZY。尝试将其更改为 FetchType.EAGER。也可以尝试设置 CascadeType.MERGE。

仅供引用，当您使用 @Data 时，您不必显式添加 getter 和 setter。