Question

我正在尝试使用hibernate和注释来实现many2many关系。

股票是主表

类别是主表

stock_category维护股票和类别之间的关系。这里有一只股票可以属于多个类别，反之亦然。

这是代码。

股票类

package com.sample.hibernate.many2many.model;

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 static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.CascadeType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;
import javax.persistence.UniqueConstraint;

@Entity
@Table(name = "stock", uniqueConstraints = {
        @UniqueConstraint(columnNames = "STOCK_NAME"),
        @UniqueConstraint(columnNames = "STOCK_CODE") })
public class Stock implements java.io.Serializable {

    private Integer stockId;
    private String stockCode;
    private String stockName;
    private Set<Category> categories = new HashSet<Category>(0);

    public Stock() {
    }

    public Stock(String stockCode, String stockName) {
        this.stockCode = stockCode;
        this.stockName = stockName;
    }

    public Stock(String stockCode, String stockName, Set<Category> categories) {
        this.stockCode = stockCode;
        this.stockName = stockName;
        this.categories = categories;
    }

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "STOCK_ID", unique = true, nullable = false)
    public Integer getStockId() {
        return this.stockId;
    }

    public void setStockId(Integer stockId) {
        this.stockId = stockId;
    }

    @Column(name = "STOCK_CODE", unique = true, nullable = false, length = 10)
    public String getStockCode() {
        return this.stockCode;
    }

    public void setStockCode(String stockCode) {
        this.stockCode = stockCode;
    }

    @Column(name = "STOCK_NAME", unique = true, nullable = false, length = 20)
    public String getStockName() {
        return this.stockName;
    }

    public void setStockName(String stockName) {
        this.stockName = stockName;
    }

    @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinTable(name = "stock_category", joinColumns = { 
            @JoinColumn(name = "STOCK_ID", nullable = false, updatable = false) }, 
            inverseJoinColumns = { @JoinColumn(name = "CATEGORY_ID", 
                    nullable = false, updatable = false) })
    public Set<Category> getCategories() {
        return this.categories;
    }

    public void setCategories(Set<Category> categories) {
        this.categories = categories;
    }

}

类别类

package com.sample.hibernate.many2many.model;


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 static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity
@Table(name = "category")
public class Category implements java.io.Serializable {

private Integer categoryId;
private String name;
private String desc;
private Set<Stock> stocks = new HashSet<Stock>(0);

public Category() {
}

public Category(String name, String desc) {
    this.name = name;
    this.desc = desc;
}

public Category(String name, String desc, Set<Stock> stocks) {
    this.name = name;
    this.desc = desc;
    this.stocks = stocks;
}

@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "CATEGORY_ID", unique = true, nullable = false)
public Integer getCategoryId() {
    return this.categoryId;
}

public void setCategoryId(Integer categoryId) {
    this.categoryId = categoryId;
}

@Column(name = "NAME", nullable = false, length = 10)
public String getName() {
    return this.name;
}

public void setName(String name) {
    this.name = name;
}

@Column(name = "[DESC]", nullable = false)
public String getDesc() {
    return this.desc;
}

public void setDesc(String desc) {
    this.desc = desc;
}

@ManyToMany(fetch = FetchType.LAZY, mappedBy = "categories")
public Set<Stock> getStocks() {
    return this.stocks;
}

public void setStocks(Set<Stock> stocks) {
    this.stocks = stocks;
}

客户端

    public class App {
    public static void main(String[] args) {

        System.out.println("Hibernate many to many (Annotation)");
    Session session = HibernateUtil.getSessionFactory().openSession();

    session.beginTransaction();

    Stock stock = new Stock();
        stock.setStockCode("7052");
        stock.setStockName("PADINI");


        Category category1 = new Category("CONSUMER", "CONSUMER COMPANY");
        Category category2 = new Category("INVESTMENT", "INVESTMENT COMPANY");



        Set<Category> categories = new HashSet<Category>();
        categories.add(category1);
        categories.add(category2);

        Set<Category> categories1 = new HashSet<Category>();
        categories1.add(category1);
        categories1.add(category2);
        stock.setCategories(categories);

        session.save(stock);

        Stock stock2 = (Stock) session.get(Stock.class, new Integer(1));
        System.out.println(stock2);
        session.delete(stock2);
         stock2 = (Stock) session.get(Stock.class, new Integer(1));
        System.out.println("after del "+stock2);
        session.getTransaction().commit();
        session.close();

        System.out.println("Done");
    }
}

当我执行上述客户端时，我在控制台中看到以下内容。

Hibernate: insert into stock (STOCK_CODE, STOCK_NAME) values (?, ?)
Hibernate: insert into category (`DESC`, NAME) values (?, ?)
Hibernate: insert into category (`DESC`, NAME) values (?, ?)
com.sample.hibernate.many2many.model.Stock@84910e8
after del null
Hibernate: delete from category where CATEGORY_ID=?
Hibernate: delete from category where CATEGORY_ID=?
Hibernate: delete from stock where STOCK_ID=?
Done

为什么hibernate也会从类别中删除？我做错了什么。

我看到的其他事情是打印完成后程序没有中止。我会做的事情很奇怪。

提前致谢

hibernate删除操作是从主表

0 个答案: