Hibernate单向关联1-N

基于外键1-N关联（无连接表）

一个Customer关联多个Card

Customer实体（1端）：

package com.ydoing.hibernate4;import java.util.HashSet;import java.util.Set;import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.OneToMany;import javax.persistence.Table;@Entity@Table(name = "customer_inf")public class Customer {    @Id    @Column(name = "customer_id")    @GeneratedValue(strategy = GenerationType.IDENTITY)    private Integer id;    private String name;    @OneToMany(targetEntity = Card.class, cascade = CascadeType.ALL)    @JoinColumn(name = "customer_id", referencedColumnName = "customer_id")    private Set<Card> cards = new HashSet<>();    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Set<Card> getCards() {        return cards;    }    public void setCards(Set<Card> cards) {        this.cards = cards;    }}

Card实体（N端）：

package com.ydoing.hibernate4;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "card_inf")public class Card {    @Id    @Column(name = "card_id")    @GeneratedValue(strategy = GenerationType.IDENTITY)    private Integer id;    private String name;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

测试：

package com.ydoing.hibernate4;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.junit.BeforeClass;import org.junit.Test;public class Main {    private static Session session;    @BeforeClass    public static void init() {        Configuration conf = new Configuration();        conf.configure();        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(conf.getProperties())                .build();        SessionFactory factory = conf.buildSessionFactory(serviceRegistry);        session = factory.openSession();    }    @Test    public void test() {        Transaction tx = session.getTransaction();        tx.begin();        Customer customer = new Customer();        customer.setName("Jack");        Card card1 = new Card();        card1.setName("ICBC");        Card card2 = new Card();        card2.setName("CCB");        customer.getCards().add(card1);        customer.getCards().add(card2);        session.save(customer);        tx.commit();        session.close();    }}  

Console输出：

Hibernate:     insert     into        customer_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        card_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        card_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     update        card_inf     set        customer_id=?     where        card_id=?Hibernate:     update        card_inf     set        customer_id=?     where        card_id=? 

从输出不难看出Hibernate主要进行了5个操作。首先向customer_inf插入一条数据，向card_inf插入两条数据。然后两次更新card_inf表。

数据表：
customer_inf:

card_inf:

有连接表的单向1-N关联

只要改变前面Customer类就行了

package com.ydoing.hibernate4;import java.util.HashSet;import java.util.Set;import javax.persistence.CascadeType;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.JoinColumn;import javax.persistence.JoinTable;import javax.persistence.OneToMany;import javax.persistence.Table;@Entity@Table(name = "customer_inf")public class Customer {    @Id    @Column(name = "customer_id")    @GeneratedValue(strategy = GenerationType.IDENTITY)    private Integer id;    private String name;    @OneToMany(targetEntity = Card.class, cascade = CascadeType.ALL)    // @JoinColumn(name = "customer_id", referencedColumnName = "customer_id")    @JoinTable(name = "customer_card_inf", joinColumns = @JoinColumn(name = "customer_id", referencedColumnName = "customer_id"), inverseJoinColumns = @JoinColumn(name = "card_id", referencedColumnName = "card_id", unique = true))    private Set<Card> cards = new HashSet<>();    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Set<Card> getCards() {        return cards;    }    public void setCards(Set<Card> cards) {        this.cards = cards;    }}

Console输出：

Hibernate:     insert     into        customer_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        card_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        card_inf        (name)     values        (?)Hibernate:     select        last_insert_id()Hibernate:     insert     into        customer_card_inf        (customer_id, card_id)     values        (?, ?)Hibernate:     insert     into        customer_card_inf        (customer_id, card_id)     values        (?, ?)

从输出不难看出，Hibernate创建了连接表customer_card_inf。

数据库表：