Spring Boot+Hibernate关联查询数据为null及EntityNotFoundException求助

问题背景 #

现有两个实体类ShippingOrder和Shipment，代码如下：

ShippingOrder实体类 #

@Entity
@Table(name="shipping_order")
@AllArgsConstructor
@NoArgsConstructor
@Getter
@Setter
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class ShippingOrder implements Serializable {
    @JsonManagedReference
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "shipment_id")
    private Shipment shipment;
}

Shipment实体类 #

@Entity
@Table(name = "shipment")
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class Shipment implements Serializable {
    @JsonBackReference
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "shipping_order_id")
    private ShippingOrder shippingOrder;
}

遇到的问题：

1. 关联字段获取数据时显示为null，但Hibernate拦截器中存在对应数据
2. 获取AWB数据时抛出异常：

Method threw 'javax.persistence.EntityNotFoundException' exception. Cannot evaluate com.hk.admin.entities.Awb$HibernateProxy$EQfa2R8Q.toString()

解决方案 #

1. 修正双向关联的注解配置 #

当前两个实体都用@ManyToOne是错误配置，双向关联需一端用@OneToMany、另一端用@ManyToOne，否则会形成两个独立单向关联，导致Hibernate无法维护关联关系，出现null值。

修改示例：

• Shipment类调整为@OneToMany，指定mappedBy指向关联字段：

@Entity
@Table(name = "shipment")
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Setter
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class Shipment implements Serializable {
    @JsonBackReference
    @OneToMany(mappedBy = "shipment", fetch = FetchType.LAZY)
    private List<ShippingOrder> shippingOrders;
}

• ShippingOrder类保持@ManyToOne，确认@JoinColumn的name对应数据库真实外键字段：

@Entity
@Table(name="shipping_order")
@AllArgsConstructor
@NoArgsConstructor
@Getter
@Setter
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
public class ShippingOrder implements Serializable {
    @JsonManagedReference
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "shipment_id") // 确认该字段在shipping_order表中存在且关联shipment表主键
    private Shipment shipment;
}

2. 解决EntityNotFoundException异常 #

该异常通常因懒加载代理在Session关闭后访问，或数据库无对应AWB记录导致：

• 维护Session生命周期：Spring环境下用@Transactional注解保证方法内Session持续打开，避免懒加载时Session已关闭。
• 验证数据库数据：检查AWB表中是否存在关联ID对应的记录，避免关联不存在的数据。
• 调整加载策略：如需立即加载AWB数据，可将关联字段的fetch改为FetchType.EAGER，或查询时用JOIN FETCH显式加载：

  // 示例JPQL查询
  String jpql = "SELECT so FROM ShippingOrder so JOIN FETCH so.shipment s JOIN FETCH s.awb WHERE so.id = :id";
  

3. 优化Json序列化配置 #

@JsonManagedReference和@JsonBackReference配置不当可能导致关联数据无法正常序列化，可替换为@JsonIdentityInfo处理循环引用：

@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@Entity
// 其他注解...
public class ShippingOrder implements Serializable {
    // 字段定义...
}

@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class, property = "id")
@Entity
// 其他注解...
public class Shipment implements Serializable {
    // 字段定义...
}

内容的提问来源于stack exchange，提问作者AasthaChaudhary