如何解决添加JPA关联后出现的com.fasterxml.jackson.databind.ser错误

问题背景 #

配置JPA实体间的ManyToOne和OneToMany关联后，出现Jackson Databind序列化错误，怀疑是关联配置导致的问题。Product实体对应Northwind数据库的产品表，关联了Category和Supplier表。

错误信息 #

at com.fasterxml.jackson.databind.ser.std.CollectionSerializer.serialize(CollectionSerializer.java:25) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:774) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:178) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:728) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:774) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:178) ~[jackson-databind-2.13.4.2.jar:2.13.4.2]

关联后的实体代码 #

Product实体 #

package com.JpaTraining.JpaTraining.entities.concretes;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import lombok.Data;

@Entity
@Data
@Table(name = "products")
public class Product {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "product_id")
    private int productId;
    @Column(name = "product_name")
    private String productName;

    @ManyToOne
    @JoinColumn(name = "supplier_id")
    private Supplier supplier;

    @ManyToOne
    @JoinColumn(name = "category_id")
    private Category category;
    @Column(name = "unit_price")
    private double unitPrice;
    @Column(name = "units_in_stock")
    private int unitsInStock;

    public Product() {
    }

    public Product(int productId, String productName, Supplier supplier, Category category, double unitPrice,
            int unitsInStock) {
        this.productId = productId;
        this.productName = productName;
        this.supplier = supplier;
        this.category = category;
        this.unitPrice = unitPrice;
        this.unitsInStock = unitsInStock;
    }
}

Category实体 #

package com.JpaTraining.JpaTraining.entities.concretes;

import java.util.List;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import lombok.Data;

@Entity
@Data
@Table(name = "categories")
public class Category {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "category_id")
    private int categoryId;
    @Column(name = "category_name")
    private String categoryName;

    @OneToMany(mappedBy = "category")
    private List<Product> product;

    public Category() {
    }

    public Category(int categoryId, String categoryName, List<Product> product) {
        this.categoryId = categoryId;
        this.categoryName = categoryName;
        this.product = product;
    }
}

Supplier实体 #

package com.JpaTraining.JpaTraining.entities.concretes;

import java.util.List;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

import lombok.Data;

@Entity
@Data
@Table(name = "suppliers")
public class Supplier {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "supplier_id")
    private int supplierId;
    @Column(name = "company_name")
    private String supplierName;

    @OneToMany(mappedBy = "supplier")
    private List<Product> product;

    public Supplier() {

    }

    public Supplier(int supplierId, String supplierName, List<Product> product) {
        this.supplierId = supplierId;
        this.supplierName = supplierName;
        this.product = product;
    }

}

数据库字符集配置 #

解决方案 #

这个错误的核心原因是实体间的双向关联导致Jackson序列化时出现循环引用：Product引用了Category/Supplier，而Category/Supplier又反过来引用了Product列表，序列化时会无限递归调用，最终抛出异常。

解决方法（按需选择）： #

1. 添加@JsonIgnore注解：在双向关联的一方忽略序列化，比如在Category和Supplier的product字段上添加：

@OneToMany(mappedBy = "category")
@JsonIgnore
private List<Product> product;

2. 使用@JsonManagedReference和@JsonBackReference：区分双向关联的主动/被动方，避免循环：

• 在Product的supplier和category字段上添加@JsonManagedReference
• 在Category和Supplier的product字段上添加@JsonBackReference

3. 使用DTO传输数据：创建专门的DTO类，只包含需要返回的字段，序列化时转换为DTO而非直接序列化实体类，彻底隔离实体关联与前端数据结构。

另外，建议将实体类中List<Product>的变量名改为products（复数形式），符合编码规范，避免歧义。

内容的提问来源于stack exchange，提问作者Emre