Hibernate多对一关系代码示例（Many-To-One）

1、创建测试表两个//没多少字段，就不写了，后面一对多和多对多都用的上
// category类型表，根据实体类的属性创建字段
// product产品表，根据实体类的属性创建字段

2、创建两个表的实体类package com.entity;

import java.util.Set;

/**
* 类型表实体
* Created by lvjun on 2018-03-26.
*/
public class CategoryEntity {
int id;
String name;

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;
}
}

package com.entity;

import java.util.Set;

/**
* 产品表实体
* Created by lvjun on 2018-03-26.
*/
public class ProductEntity {
int id;
String name ;
float price;

// 添加类型CategoryEntity属性
CategoryEntity categoryEntity;

public CategoryEntity getCategoryEntity() {
return categoryEntity;
}

public void setCategoryEntity(CategoryEntity categoryEntity) {
this.categoryEntity = categoryEntity;
}

//产品表构建参数
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 float getPrice() {
return price;
}

public void setPrice(float price) {
this.price = price;
}
}

3、创建映射配置文件，包含数据库配置
1、CategoryEntity.hbm.xml<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.entity">
<class name="CategoryEntity" table="category">
<id name="id" column="id">
<generator class="native"></generator>
</id>
<property name="name" />
</class>

</hibernate-mapping>2、ProductEntity.hbm.xml<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.entity">
<class name="ProductEntity" table="product">
<id name="id" column="id">
<generator class="native"></generator>
</id>
<property name="name" />
<property name="price" />
        <!--
            设置类型表多对一关系：
            name =对应ProductEntity实体类中CategoryEntity的属性
            class= 对应CategoryEntity实体类
            column=指向 category表的外键 ，在product表中会新增cid字段
        -->
        <many-to-one name="categoryEntity" class="CategoryEntity" column="cid" />
</class>

</hibernate-mapping>4、创建hibernate.cfg.xml核心配置文件src路径下，别进包里去了<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>

<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/school?characterEncoding=GBK</property>
<property name="connection.username">root</property>
<property name="connection.password">1234</property>
<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="current_session_context_class">thread</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>
<!--实体映射-->
<mapping resource="com/entity/Category.hbm.xml"/>
<mapping resource="com/entity/ProductEntity.hbm.xml"/>
</session-factory>

</hibernate-configuration>5、创建测试类package com.test;

import com.entity.CategoryEntity;
import com.entity.ProductEntity;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

/**
* 多对一关系
* 多个产品对应一个类型
* Created by lvjun on 2018-03-26.
*/
public class ManyToOne {
public static void main(String[] args) {
SessionFactory sessionFactory =new Configuration().configure().buildSessionFactory();
Session session =sessionFactory.openSession();
        //开启事物
session.beginTransaction();

//添加一个安卓的类型
CategoryEntity categoryEntity =new CategoryEntity();
categoryEntity.setName("安卓");
session.save(categoryEntity);

//产品表中id为8的产品，将其类型改成类型表中的id，在配置文件里面有一个新增cid字段
ProductEntity productEntity= (ProductEntity) session.get(ProductEntity.class,8);
productEntity.setCategoryEntity(categoryEntity);
session.update(productEntity);

//提交并关闭
session.beginTransaction().commit();
session.close();
sessionFactory.close();

}
}