向实体添加动态列而不将其保存到 table

Question

我有一个模型 class 如下所示：

package com.example.model;
import java.util.Map;

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

import com.example.helpers.StringMapConverter;
@Entity
@Table(name = "buildingcompanies")

public class Buildcompanies {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;
    @Column(name = "shortname")
    private String shortname;
    @Column(name = "fullname")
    private String fullname;
    @Column(name = "address")
    private String address;
    @Column(name = "telephone")
    private String telephone;
    @Column(name = "website")
    private String website;
    @Column(name = "sociallinks")
      @Convert(converter = StringMapConverter.class)

    private  Map<String, String> sociallinks;
    @Column(name = "foundationyear")
    private String foundationyear;
    
    public Buildcompanies() {

    }

    public Buildcompanies(String shortname, String fullname, String address, String telephone, String website,
            Map<String, String> map, String foundationyear) {
        this.shortname = shortname;
        this.fullname = fullname;
        this.address = address;
        this.telephone = telephone;
        this.website = website;
        this.sociallinks = map;
        this.foundationyear = foundationyear;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getShortname() {
        return shortname;
    }

    public void setShortname(String shortname) {
        this.shortname = shortname;
    }

    public String getFullname() {
        return fullname;
    }

    public void setFullname(String fullname) {
        this.fullname = fullname;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public String getWebsite() {
        return website;
    }

    public void setWebsite(String website) {
        this.website = website;
    }

    

    public Map<String, String> getSociallinks() {
        return sociallinks;
    }

    public void setSociallinks(Map<String, String> sociallinks) {
        this.sociallinks = sociallinks;
    }

    public String getFoundationyear() {
        return foundationyear;
    }

    public void setFoundationyear(String foundationyear) {
        this.foundationyear = foundationyear;
    }
    
    
    
    
    
    
}

以及控制器中显示输出的方法：

public ResponseEntity<List<Buildcompanies>> getAllCompanies(@RequestParam(required = false) String name) {
      try {
        List<Buildcompanies> companies = new ArrayList<Buildcompanies>();
        int test=0;
        if (name == null)
        {
            buildcompaniesRepository.findAll().forEach(companies::add);
            
        }
        else
          buildcompaniesRepository.findByShortnameContaining(name).forEach(companies::add);

        if (companies.isEmpty()) {
          return new ResponseEntity<>(HttpStatus.NO_CONTENT);
        }

        return new ResponseEntity<>(companies, HttpStatus.OK);
      } catch (Exception e) {
        return new ResponseEntity<>(null, HttpStatus.INTERNAL_SERVER_ERROR);
      }
    }

它确实显示输出一切正常：

[
    {
        "id": 81,
        "shortname": "testing",
        "fullname": "test",
        "address": "addrtest",
        "telephone": "380979379992",
        "website": "www.site.com",
        "sociallinks": {
            "facebook": "fb.com"
        },
        "foundationyear": "1991"
    }

]

我想在向最终用户显示数据的同时计算每个公司的评级。所以输出应该如下：

[
    {
        "id": 81,
        "shortname": "testing",
        "fullname": "test",
        "address": "addrtest",
        "telephone": "380979379992",
        "website": "www.site.com",
        "sociallinks": {
            "facebook": "fb.com"
        },
        "foundationyear": "1991",
"rating": "1.5"
    }
]

是否可以将评级列动态添加到公司列表中，或者我应该在数据库中创建评级列，在控制器中更新它的方法，迭代 findAll() 结果并在每次用户尝试时调用它访问 /list 端点？

Answer 1

你有两个选择：

您可以为此目的在 Buildcompanies class 中引入一个新属性并用@Transient 对其进行注释。这将表示该属性不需要保留在数据库中，并且 JPA 不会尝试在 table.
中创建列
推荐的方法是不使用实体 class 作为响应对象。理想情况下，您应该有一个域对象，并且数据库响应应该映射到该对象。在映射时，您可以应用要添加的任何自定义详细信息。

Answer 2

只需将 @Transient 注释添加到您的动态字段。数据库中不需要相应的列。 transient 列的值只存在于运行时。

一般来说，出于多种原因，将实体作为 JSON 与外部系统共享是个坏主意。请改用中间 DTO。有很多库允许从实体到 DTO 的可配置自动映射（ModelMapper 对我来说非常好）。

向实体添加动态列而不将其保存到 table

add a dynamic column to an entity without saving it to the table

java

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spring-boot