在JPA双向@OnetoMany关系中，当我更新父实体时，子实体在数据库中被删除

Posted 2023-04-12

【中文标题】在JPA双向@OnetoMany关系中，当我更新父实体时，子实体在数据库中被删除

【英文标题】：In JPA bidirectional @OnetoMany relationship, when I update the parent entity, the child entities are deleted in database

【发布时间】：2019-01-31 10:58:21

【问题描述】：

当我将 orphanRemoval=true 更改为 false 时，实体不会被删除，但不会在更新父实体后加载到 json 文件中。这是我下面的代码。 模型类： Market.java：

    package main.java.model;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import javax.persistence.*;
import javax.xml.bind.annotation.XmlRootElement;

import org.codehaus.jackson.annotate.JsonIgnoreProperties;

@XmlRootElement(name="somename")
@Entity
@JsonIgnoreProperties(ignoreUnknown=true)
@Table(name = "market")
@SecondaryTable(name="product",pkJoinColumns=@PrimaryKeyJoinColumn(name="market_id"))
@NamedQuery(name = "findMarket", 
query = "SELECT distinct m FROM Market m, Product p where m.id = p.market_id")
public class Market implements Serializable

    public List<Product> getProducts() 
        return products;
    

    public void setProducts(List<Product> products) 
        this.products = products;
    

    private static final long serialVersionUID = 1L;

    @Column(name = "market_name")
    private String market_name;

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private int id;

    @Column(name = "Online_Market_Accessibility")
    private String oma;

    @OneToMany(mappedBy="market", cascade=CascadeType.ALL, orphanRemoval=false)
    @JoinColumn(name="id", nullable=false)
    private List<Product> products = new ArrayList<>();

    public Market() 
    

    

    public Market(String market_name,int id, String oma)
    
        this.market_name = market_name;
        this.id = id;
        this.oma = oma;
    

    public String getMarket_name() 
        return market_name;
    

    public void setMarket_name(String market_name) 
        this.market_name = market_name;
    


    public int getId() 
        return id;
    

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

    public String getOma() 
        return oma;
    

    public void setOma(String oma) 
        this.oma = oma;
    

    @Override
    public int hashCode() 
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        result = prime * result + ((market_name == null) ? 0 : market_name.hashCode());
        result = prime * result + ((oma == null) ? 0 : oma.hashCode());
        return result;
    

    @Override
    public boolean equals(Object obj) 
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Market other = (Market) obj;
        if (id != other.id)
            return false;
        if (market_name == null) 
            if (other.market_name != null)
                return false;
         else if (!market_name.equals(other.market_name))
            return false;
        if (oma == null) 
            if (other.oma != null)
                return false;
         else if (!oma.equals(other.oma))
            return false;
        return true;
    

    @Override
    public String toString() 
        return "[market_name:"+ market_name + ", id:" + id +", oma:"+oma+"]";
    

Product.java：

    package main.java.model;

import java.io.Serializable;

import javax.persistence.*;

@Entity
@NamedQuery(name = "findProductByMarketId", 
query = "SELECT distinct p " +
        "FROM Market m, Product p where m.id = p.market.id")
public class Product implements Serializable

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private int product_id;

    private String product_name;

    private int market_id;

    @ManyToOne
    @JoinColumn(name="market_id", insertable=false, updatable=false, nullable=false)
    private Market market;

    public Product() 

    

    public Product(String product_name, int product_id, int market_id)
    
        this.product_id = product_id;
        this.product_name = product_name;
        this.market_id = market_id;
    

    public String getProduct_name() 
        return product_name;
    

    public void setProduct_name(String product_name) 
        this.product_name = product_name;
    

    public int getProduct_id() 
        return product_id;
    

    public void setProduct_id(int product_id) 
        this.product_id = product_id;
    

    public int getMarket_id() 
        return market_id;
    

    public void setMarket_id(int market_id) 
        this.market_id = market_id;
    

    @Override
    public int hashCode() 
        final int prime = 31;
        int result = 1;
        result = prime * result + market_id;
        result = prime * result + product_id;
        result = prime * result + ((product_name == null) ? 0 : product_name.hashCode());
        return result;
    

    @Override
    public boolean equals(Object obj) 
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Product other = (Product) obj;
        if (market_id != other.market_id)
            return false;
        if (product_id != other.product_id)
            return false;
        if (product_name == null) 
            if (other.product_name != null)
                return false;
         else if (!product_name.equals(other.product_name))
            return false;
        return true;
    

    @Override
    public String toString() 
        return "Product [name=" + product_name + ", Product Id =" + product_id + "]";
    

这是我的 dao 实现

    package main.java.services;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.persistence.Query;

import main.java.dao.MarketDao;
import main.java.model.Market;

public class MarketService implements MarketDao

    EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPU");
    EntityManager em = emf.createEntityManager();

    public List<Market> getAllMarkets()
        Query query = em.createNamedQuery("findMarket");
        List<Market> m = query.getResultList();
        return m;
    

    public void updateMarket(int id, String market_name, Market market) 
        em.getTransaction().begin();
        Query query = em.createQuery("UPDATE Market SET market_name=:market_name WHERE id=:id");
        query.setParameter("id", id);
        query.setParameter("market_name", market_name);
        em.merge(market);
        em.getTransaction().commit();
    

    public void deleteMarket(int id) 
        Market market = em.find(Market.class, id);
        if(null != market) 
            em.remove(market);
        
    

    public void addMarket(Market market) 
        em.getTransaction().begin();
        em.persist(market);
        em.getTransaction().commit();
    

我已尝试更改我的级联类型，但没有成功。请帮忙。

我更新前的 JSON 文件：

[

    "id": 2,
    "products": [
        
            "product_id": 4,
            "market_id": 2,
            "product_name": "Apple"
        ,
        
            "product_id": 5,
            "market_id": 2,
            "product_name": "Samsung"
        
    ],
    "oma": "Yes",
    "market_name": "SmartPhones"
,

    "id": 3,
    "products": [
        
            "product_id": 6,
            "market_id": 3,
            "product_name": "Ranbaxy"
        
    ],
    "oma": null,
    "market_name": "Pharmaceuticals"
,

    "id": 1,
    "products": [
        
            "product_id": 3,
            "market_id": 1,
            "product_name": "Emirates"
        ,
        
            "product_id": 2,
            "market_id": 1,
            "product_name": "PANAmerican"
        ,
        
            "product_id": 1,
            "market_id": 1,
            "product_name": "Indigo"
        
    ],
    "oma": null,
    "market_name": "Airline Travels"
,

    "id": 4,
    "products": [
        
            "product_id": 7,
            "market_id": 4,
            "product_name": "Cake"
        
    ],
    "oma": null,
    "market_name": "Baked Good"

]

还有我更新后的 JSON 文件：

[
    
        "id": 2,
        "market_name": "SmartPhones",
        "oma": "Yes",
        "products": [
            
                "product_id": 4,
                "product_name": "Apple",
                "market_id": 2
            ,
            
                "product_id": 5,
                "product_name": "Samsung",
                "market_id": 2
            
        ]
    ,
    
        "id": 3,
        "market_name": "Pharmaceuticals",
        "oma": null,
        "products": [
            
                "product_id": 6,
                "product_name": "Ranbaxy",
                "market_id": 3
            
        ]
    ,
    
        "id": 1,
        "market_name": "Airline Travels",
        "oma": null,
        "products": []
    ,
    
        "id": 4,
        "market_name": "Baked Good",
        "oma": null,
        "products": [
            
                "product_id": 7,
                "product_name": "Cake",
                "market_id": 4
            
        ]
    
]

但是，数据存在于数据库中。当我重新启动服务器时，它已加载。

这是我的控制器：

@Transactional
@Path("/json/market")
public class MarketContoller 

    MarketService ms = new MarketService();

    @GET
    @Path("/get")
    @Produces(MediaType.APPLICATION_JSON)
    public List<Market> listAllMarket()
         return ms.getAllMarkets();
    

    @PUT
    @Path("/put/id")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response update(@PathParam("id") int id, @PathParam("market_name") String market_name, Market market) 
        String result = "Market updated " + market;
        ms.updateMarket(id, market_name);
        return Response.status(201).entity(result).build();
    

     @DELETE
     @Path("id")
     public void delete(@PathParam("id") int id) 
            ms.deleteMarket(id);
            

    @POST
    @Path("/post")
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public Response createMarketInJSON(Market market) 
        String result = "Market created " + market;
        ms.addMarket(market);   
        return Response.status(201).entity(result).build();
    

【问题讨论】：

updateMarket方法中的查询根本没有用到。您所做的就是合并传入的市场对象。那个物体是从哪里来的？我假设您从传入的 json 创建它。如果传入的 json 不包含所有相关产品，那么当您合并它时，持久市场当然将不再包含这些关系。

但是，传入的 json 包含所有相关产品。但是当我合并它时，持续的市场不再包含这些关系

这可能与***.com/questions/5460573/…重复

【参考方案1】：

我不知道你的控制器是什么样子的，但那里有些东西搞砸了。 因为您在更新期间覆盖了市场，所以至少 id 是正确的。所以试试这个：

public void updateMarket(int id, String market_name) 
    em.getTransaction().begin();
    Market market = em.find(Market.class, id);
    if(null != market) 
        market.setMarket_name(market_name);
        em.merge(market);
    
    em.getTransaction().commit();

【讨论】：

我使用了这段代码，现在产品没有被删除，但是数据库中的 market_name 设置为 null

【参考方案2】：

我已经解决了这个问题。我对更新代码做了一点改动：

public void updateMarket(int id, String market_name, Market market) 
    em.getTransaction().begin();
    Query query = em.createQuery("UPDATE Market SET market_name=:market_name WHERE id=:id");
    query.setParameter("id", id);
    query.setParameter("market_name", market_name);
    query.executeUpdate();
    em.merge(market);
    em.getTransaction().commit();