ModelMapper 在尝试将 Entity 映射到 DTO 对象时返回 NULL

Question

这是我尝试映射的对象的类：

package com.agent.module.entities;


import java.util.Set;

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;

import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;
import lombok.experimental.Accessors;

@Entity
@Getter @Setter @NoArgsConstructor
@Accessors
public class Accommodation {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String location;
    @ManyToOne(optional=false, fetch=FetchType.EAGER)
    private AccommodationType type;

    private String description;

    private String name;
    @OneToMany(orphanRemoval=true, fetch=FetchType.EAGER)
    @Cascade(CascadeType.ALL)
    private Set<Document> images;

    private Integer capacity;
    @ManyToMany(fetch=FetchType.EAGER)
    private Set<AdditionalService> additionalServices;

    @OneToMany(orphanRemoval=true, fetch=FetchType.EAGER)
    @Cascade(CascadeType.ALL)
    private Set<PricePlan> pricePlan;

    @ManyToOne(optional=false, fetch=FetchType.LAZY)
    private Agent agent;

    @OneToMany(orphanRemoval=true, mappedBy="accommodation", fetch=FetchType.EAGER)
    @Cascade(CascadeType.ALL)
    private Set<Restriction> restrictions;

    @ManyToOne(fetch=FetchType.EAGER)
    private Category category;

    @Override
    public String toString() {
        return "Name: "+name+"\n"+"Agent PIB: "+agent.toString()+"\n";
    }

}

这是我的 DTO 对象：

package com.agent.module.dto;

import java.util.List;

import javax.xml.bind.annotation.XmlRootElement;

import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

@Getter @Setter @NoArgsConstructor
@XmlRootElement
public class AccommodationView {
    private Long id;
    private String location;
    private String typeName;
    private String description;
    private String name;
    private List<String> imagesPath;
    private Integer capacity;
    private List<String> additionalServicesName;
    private List<PricePlanView> pricePlan;
    private String agentUsername;
    private List<RestrictionView> restrictions;
    private String categoryName;

    @Override
    public String toString() {
        return "ID: "+id+"\n"+"Type: "+typeName+"\n"+"Description: "+description+"\n"+"Category: "+categoryName+"\n"+"Name: "+name+"\n";
    }

}

当我打开 Postman 并尝试从

MySQL

数据库获取所有 Accommodation 对象时，我实际上想要获取 DTO 对象，为了做到这一点，我正在使用

ModelMapper

。但由于某种原因，每次我尝试将

Accommodation

映射到

AccommodationView

时，我都会得到 Null 作为回报。这是我尝试执行映射的类：

@RestController
@RequestMapping(value = "/accommodation")
public class AccommodationController {

    @Autowired
    AccommodationRepo accommodationRepo;

    @Autowired 
    ModelMapper mapper;

    @RequestMapping(value="/all",
            method = RequestMethod.GET,
            produces = MediaType.APPLICATION_JSON_VALUE)
    @ResponseBody
    ResponseEntity<List<AccommodationView>> getAll(){
        List<Accommodation> accommodations = accommodationRepo.findAll();

        List<AccommodationView> accommodationViewList= new ArrayList<AccommodationView>();

        for(Accommodation accommodation : accommodations) {
            System.out.println(accommodation);
            System.out.println(convertToDto(accommodation));
            accommodationViewList.add(convertToDto(accommodation));
        }

        return new ResponseEntity<List<AccommodationView>>(accommodationViewList, HttpStatus.OK);
    }

    private AccommodationView convertToDto(Accommodation accommodation) {
        return mapper.map(accommodation, AccommodationView.class);
    }

    private Accommodation convertToEntity(AccommodationView accommodationView) {
        return mapper.map(accommodationView, Accommodation.class);
    }
}

这是我点击该方法时得到的输出：

Name: Test
Agent PIB: 2308995710368

ID: null
Type: null
Description: null
Category: null
Name: null

输出的第一部分来自

Accommodation

对象，输出的第二部分来自

AccommodationView

对象。如果有人知道发生了什么事，我将非常感谢您的帮助。

Answer 1

您必须为您的情况（住宿实体）的目标类生成公共设置函数。否则 Modelmapper 无法访问类的私有字段来设置它们的值。

Answer 2

我建议两种解决方案来解决您的问题。

解决方案1

在您的 dto 对象 AccommodationView 中尝试添加

@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)

。或者为每个 dto 字段添加注释

@JsonPrperty

。这两种方法可以帮助映射 dto 对象和 json 邮递员响应。

解决方案2

看来您遇到的问题与mapstruct或/和lombok有关。我建议您检查生成的映射器实现映射结构文件 ModelMapperImpl 是否看起来不错（您应该为每个实体字段提供一条与 dto 关联字段映射的指令，或/反之亦然）。

如果不是这种情况，请检查 pom.xml 或 build.gradle 文件中是否正确配置了 lombok、mapstruct 和 lombok-mapstruct-binding deps（这里是使用 maven 实现此实现的示例）。另外，对于您的 IDE，检查 lombok 是否配置良好（通过安装 lombok 插件并启用注释处理器）