Hibernate关系的理解和使用

多对一

//Product的类
package com.spike.pojo;
import com.spike.pojo.Category;

public class Product{
	private int id;
	private String name;
	private Category category;

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

	public void setCategory(Category category){
		this.category = category;
	}

	public int getId(){	return this.id; }
	public String getName(){ return this.name; }
	public Category getCategory(){ return this.category; }
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="Product" table="product_">
		<id name="id" column="id">
			<generator class="native"></generator>
		</id>
		<property name="name" column="name"></property>
		<many-to-one class="Category" name="category" column="cid"></many-to-one>
	</class>
</hibernate-mapping>

其中标签中
name=“category” 对应 Product 中的category属性
class=“Category” 对应 category对应的Category类
column=“cid” 对应 product_表的cid数据

一对多

package com.spike.pojo;

import com.spike.pojo.Product;
import java.util.Set;

public class Category{
	private int id;
	private String name;
	private Set<Product> products;

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

	public void setProducts(Set<Product> products){
		this.products = products;
	}

	public int getId(){	return this.id; }
	public String getName(){ return this.name; }
	public Set<Product> getProducts(){ return this.products; }
	
}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="Category" table="category_">
		<id name="id" column="id">
			<generator class="native"></generator>
		</id>
		<property name="name" column="name"></property>
		<set name="products" lazy="false">
			<key column="cid"></key>
			<one-to-many class="Product"></one-to-many>
		</set>
	</class>
</hibernate-mapping>

<“set”>标签中
name 对应于 Category 属性products
<“key”>中
column 中的 cid 与 category_表中的 id 一致

多对多

Java代码就按照UML图就行了
XML代码

Product差异
<set name="users" table="user_product" lazy="false">
	<key column="pid"></key>
	<many-to-many class="User" column="uid"></many-to-many>
</set>

set标签中
name对应于Product属性中的users
table中的表 user_product , 根据多对多原则,将Product中的主码id与User中的主码id合成的一个新表
key标签中
product_表中的id对应user_product中的pid
many-to-many标签中
class对应类User 其id对应user_product中的uid

这是基于对how2J代码的理解，错误的麻烦指正
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