Question

我正在开发一个使用hibernate的简单练习应用程序。它具有简单的映射，就像制造商可以拥有许多手机一样。但移动设备只能由单一制造商生产。这是我认为代码应该是什么。

package mobileconsumers.entity.dto;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;


@Entity
@Table(name="ms_ref_mobile")
public class MobileDTO {

private Long id;
private String model;
private ManufacturerDTO manufacturerDTO;

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="MOBILE_ID")
public Long getId() {
    return id;
}
public void setId(Long id) {
    this.id = id;
}
public String getModel() {
    return model;
}
public void setModel(String model) {
    this.model = model;
}
@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="MANUFACTURER_ID")
public ManufacturerDTO getManufacturer() {
    return manufacturerDTO;
}
public void setManufacturer(ManufacturerDTO manufacturer) {
    this.manufacturerDTO = manufacturer;
}


}

这是第二个dto

package mobileconsumers.entity.dto;

import java.util.HashSet;
import java.util.Set;

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

@Entity
@Table(name="ms_ref_manufacturer")
public class ManufacturerDTO {

private Long id;
private String name;
private Set<MobileDTO> mobileDTOs = new HashSet<>(0);

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="MANUFACTURER_ID")
public Long getId() {
    return id;
}
public void setId(Long id) {
    this.id = id;
}
@Column(name="NAME")
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
@OneToMany(fetch=FetchType.LAZY,mappedBy="manufacturerDTO")
public Set<MobileDTO> getMobileDTOs() {
    return mobileDTOs;
}
public void setMobileDTOs(Set<MobileDTO> mobileDTOs) {
    this.mobileDTOs = mobileDTOs;
}


}

当我尝试启动服务器时，它给出了一个错误说... org.hibernate.AnnotationException: mappedBy reference anunknown target entity property: mobileconsumers.entity.dto.MobileDTO.manufacturerDTO in mobileconsumers.entity.dto.ManufacturerDTO.mobileDTOs 映射似乎对我来说没问题。我错过了一些非常愚蠢的东西。只需要新鲜的双眼来看我的代码并弄清楚什么是错的..

Answer 1

更改mappedBy值，以便它引用关联的manufacturer一侧的@ManyToOne属性：

@OneToMany(fetch=FetchType.LAZY,mappedBy="manufacturer")
public Set<MobileDTO> getMobileDTOs() {
    return mobileDTOs;
}

：mappedBy引用未知的目标实体属性

1 个答案: