Hibernate ORM 之 单向一对多

Hibernate ORM 之 单向一对多

单向一对多：一方持有多方的集合。在一方持有多方的集合上使用@OneToMany和@JoinColumn注解

1 pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">    <modelVersion>4.0.0</modelVersion>    <groupId>com.libill</groupId>    <artifactId>hibernate-demo</artifactId>    <packaging>war</packaging>    <version>1.0-SNAPSHOT</version>    <name>hibernate-demo Maven Webapp</name>    <url>http://maven.apache.org</url>    <dependencies>        <!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->        <dependency>            <groupId>org.hibernate</groupId>            <artifactId>hibernate-core</artifactId>            <version>5.2.10.Final</version>        </dependency>        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->        <dependency>            <groupId>mysql</groupId>            <artifactId>mysql-connector-java</artifactId>            <version>5.1.38</version>        </dependency>        <dependency>            <groupId>junit</groupId>            <artifactId>junit</artifactId>            <version>4.12</version>        </dependency>    </dependencies>    <build>        <finalName>hibernate-demo</finalName>    </build></project>

2 hibernate.cfg.xml配置文件

<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration>    <session-factory>        <property name="connection.url">jdbc:mysql://192.168.145.128:3306/hibernate?useUnicode=true&amp;characterEncoding=utf-8</property>        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>        <property name="connection.username">root</property>        <property name="connection.password">123456</property>        <property name="connection.autocommit">false</property>        <!-- DB schema will be updated if needed -->        <property name="hbm2ddl.auto">update</property>        <!-- 显示sql语句 -->        <property name="show_sql">true</property>        <!-- 显示sql语句前进行格式化 -->        <property name="format_sql">true</property>        <!-- 方言： MySQL55Dialect将会使用InnoDB引擎 -->        <property name="dialect">org.hibernate.dialect.MySQL55Dialect</property>        <mapping class="com.libill.beans.Customer"/>        <mapping class="com.libill.beans.Order"/>    </session-factory></hibernate-configuration>

3 实体类

package com.libill.beans;import javax.persistence.*;import java.util.HashSet;import java.util.Set;@Entity@Table(name = "t_customer")@SuppressWarnings(value = {"unused"})public class Customer {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    private String name;    private String phone;    @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)    // 指定订单表外键字段名称为cid，它的值为Customer中的id，外键名称为fk_c_o    @JoinColumn(name = "cid", foreignKey = @ForeignKey(name = "fk_c_o"))    private Set<Order> orders = new HashSet<Order>();    public Customer() {    }    public Customer(String name, String phone) {        this.name = name;        this.phone = phone;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getPhone() {        return phone;    }    public void setPhone(String phone) {        this.phone = phone;    }    public Set<Order> getOrders() {        return orders;    }    public void setOrders(Set<Order> orders) {        this.orders = orders;    }}

package com.libill.beans;import com.sun.istack.internal.Nullable;import javax.persistence.*;@Entity@Table(name = "t_order")@SuppressWarnings(value = {"unused"})public class Order {    @Id    @GeneratedValue(strategy = GenerationType.IDENTITY)    private int id;    private String content;    public Order() {    }    public Order(String content) {        this.content = content;    }    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getContent() {        return content;    }    public void setContent(String content) {        this.content = content;    }}

4 测试类

package com.libill.beans;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.boot.Metadata;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.hibernate.tool.schema.TargetType;import org.junit.After;import org.junit.Before;import org.junit.Test;import java.util.EnumSet;@SuppressWarnings(value = {"unused"})public class BeansTest {    private SessionFactory sessionFactory;    private Session session;    private Transaction transaction;    private SchemaExport schemaExport;    @Before    public void init() {        Configuration configuration = new Configuration().configure();        sessionFactory = configuration.buildSessionFactory();        session = sessionFactory.openSession();        transaction = session.beginTransaction();    }    @After    public void destroy() {        transaction.commit();        session.close();        sessionFactory.close();    }    /**     * 测试实体对象的保存     */    @Test    public void saveTest() {        Customer customer = new Customer("张三", "13982502467");        Order order = new Order("馒头");        customer.getOrders().add(order);        session.save(customer);    }    /**     * 测试根据实体对象生成数据库表，只创建表     */    @Test    public void testSchema() {        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build();        Metadata metadata = new MetadataSources(serviceRegistry).buildMetadata();        SchemaExport schemaExport = new SchemaExport();        schemaExport.create(EnumSet.of(TargetType.DATABASE), metadata);    }}

5 结果