我得到数据绑定错误。错误发生在连接manyToOne和oneToMany之后。我怀疑这一点。

• 产品类包含属于类别和供应商的多个记录（罗斯文数据库）
• • 错误：**

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]

当我在此处添加连接注解时，问题就开始了：

• • 产品实体：**

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;
    }
}

• • 类别实体：**

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;
    }
}

• • 供应商实体：**

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;
    }

}

• • 字符集：**

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