Hibernate的多对多映射

一、创建Java工程，新建Lib文件夹，加入Hibernate和数据库（如MySql、Oracle、SqlServer等）的Jar包，创建 hibernate.cfg.xml 文件，并配置，配置项如下：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-configuration PUBLIC
 3         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
 4         "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
 5 <hibernate-configuration>
 6     <session-factory>
 7     
 8         <!-- 配置连接数据库的基本信息 -->
 9         <property name="connection.username">root</property>
10         <property name="connection.password"></property>
11         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
12         <!-- <property name="connection.url">jdbc:mysql:///mis</property> -->
13         <property name="connection.url">
14             <![CDATA[jdbc:mysql://localhost:3306/mis?useUnicode=true&characterEncoding=utf8]]>
15         </property>
16 
17 
18         <!-- 配置 hibernate 的基本信息 -->
19         <!-- hibernate 所使用的数据库方言 -->
20         <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
21 
22         <!-- 执行操作时是否在控制台打印 SQL -->
23         <property name="show_sql">true</property>
24 
25         <!-- 是否对 SQL 进行格式化 -->
26         <property name="format_sql">true</property>
27 
28         <!-- 指定自动生成数据表的策略 -->
29         <property name="hbm2ddl.auto">update</property>
30         
31         <!-- 设置 Hibernate 的事务隔离级别 2:读已提交的记录-->
32         <property name="connection.isolation">2</property>
33         
34         <!-- 删除对象后, 使其 OID 置为 null -->
35         <property name="use_identifier_rollback">true</property>
36         
37         <!-- 配置 C3P0 数据源 -->
38         <property name="hibernate.c3p0.max_size">10</property>
39         <property name="hibernate.c3p0.min_size">5</property>
40         <property name="c3p0.acquire_increment">2</property>
41         
42         <property name="c3p0.idle_test_period">2000</property>
43         <property name="c3p0.timeout">2000</property>
44         
45         <property name="c3p0.max_statements">10</property>
46         
47         <!-- 设定 JDBC 的 Statement 读取数据的时候每次从数据库中取出的记录条数 -->
48         <property name="hibernate.jdbc.fetch_size">100</property>
49         
50         <!-- 设定对数据库进行批量删除，批量更新和批量插入的时候的批次大小 -->
51         <property name="jdbc.batch_size">30</property>
52 
53         <!-- 指定关联的 .hbm.xml 文件 -->    
54         <!--  
55         <mapping resource="com/mcs/hibernate/entities/onetoone/foreign/Manager.hbm.xml" />
56         <mapping resource="com/mcs/hibernate/entities/onetoone/foreign/Department.hbm.xml" />
57           -->
58         <!--   
59         <mapping resource="com/mcs/hibernate/entities/onetoone/primary/Manager.hbm.xml" />
60         <mapping resource="com/mcs/hibernate/entities/onetoone/primary/Department.hbm.xml" />
61          -->
62         <!-- 
63         <mapping resource="com/mcs/hibernate/entities/manytomany/Category.hbm.xml" />
64         <mapping resource="com/mcs/hibernate/entities/manytomany/Product.hbm.xml" />
65          -->
66         <!--  
67         <mapping resource="com/mcs/hibernate/entities/subclass/Person.hbm.xml" />
68          -->
69         <!--  
70         <mapping resource="com/mcs/hibernate/entities/joined/subclass/Person.hbm.xml" />
71          -->
72         
73         <mapping resource="com/mcs/hibernate/entities/union/subclass/Person.hbm.xml" />
74         
75 
76     </session-factory>
77 
78 </hibernate-configuration>
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二、建立多对多的映射

1、创建Java实体类

 1 package com.mcs.hibernate.entities.manytomany;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 public class Category {
 7     
 8     private Integer id;
 9     private String name;
10     
11     private Set<Product> products = new HashSet<>();
12 
13     public Integer getId() {
14         return id;
15     }
16 
17     public void setId(Integer id) {
18         this.id = id;
19     }
20 
21     public String getName() {
22         return name;
23     }
24 
25     public void setName(String name) {
26         this.name = name;
27     }
28 
29     public Set<Product> getProducts() {
30         return products;
31     }
32 
33     public void setProducts(Set<Product> products) {
34         this.products = products;
35     }
36     
37     
38 
39 }
View Code
 1 package com.mcs.hibernate.entities.manytomany;
 2 
 3 import java.util.HashSet;
 4 import java.util.Set;
 5 
 6 public class Product {
 7     
 8     private Integer id;
 9     private String name;
10     
11     private Set<Category> categories = new HashSet<>();
12     
13     public Integer getId() {
14         return id;
15     }
16     public void setId(Integer id) {
17         this.id = id;
18     }
19     public String getName() {
20         return name;
21     }
22     public void setName(String name) {
23         this.name = name;
24     }
25     public Set<Category> getCategories() {
26         return categories;
27     }
28     public void setCategories(Set<Category> categories) {
29         this.categories = categories;
30     }
31     
32     
33 
34 }
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2、根据实体类创建对应的 hbm.xml文件

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 <!-- Generated 2015-10-28 14:53:27 by Hibernate Tools 3.5.0.Final -->
 5 <hibernate-mapping>
 6     <class name="com.mcs.hibernate.entities.manytomany.Category" table="CATEGORIES">
 7         <id name="id" type="java.lang.Integer">
 8             <column name="ID" />
 9             <generator class="native" />
10         </id>
11         <property name="name" type="java.lang.String">
12             <column name="NAME" />
13         </property>
14         
15         <!-- table: 指定中间表 -->
16         <set name="products" table="CATEGORIES_PRODUCTS" inverse="true">
17             <key>
18                 <column name="CATEGORY_ID" />
19             </key>
20             <!-- 使用 many-to-many 指定多对多的关联关系. column 执行 Set 集合中的持久化类在中间表的外键列的名称  -->
21             <many-to-many class="com.mcs.hibernate.entities.manytomany.Product" column="PRODUCT_ID"/>
22         </set>
23     </class>
24 </hibernate-mapping>
View Code
 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 3 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 4 <!-- Generated 2015-10-28 14:53:27 by Hibernate Tools 3.5.0.Final -->
 5 <hibernate-mapping>
 6     <class name="com.mcs.hibernate.entities.manytomany.Product" table="PRODUCTS">
 7         <id name="id" type="java.lang.Integer">
 8             <column name="ID" />
 9             <generator class="native" />
10         </id>
11         <property name="name" type="java.lang.String">
12             <column name="NAME" />
13         </property>
14         
15         <!-- table: 指定中间表 -->
16         <set name="categories" table="CATEGORIES_PRODUCTS">
17             <key>
18                 <column name="PRODUCT_ID" />
19             </key>
20             <!-- 使用 many-to-many 指定多对多的关联关系. column 执行 Set 集合中的持久化类在中间表的外键列的名称  -->
21             <many-to-many class="com.mcs.hibernate.entities.manytomany.Category" column="CATEGORY_ID"/>
22         </set>
23     </class>
24 </hibernate-mapping>
View Code

3、备注：

　　1、使用 many-to-many 指定多对多的关联关系.

　　　　table: 指定中间表

　　　　Key：当前持久化类在中间表的外键列的名称

　　　　column：执行 Set 集合中的持久化类在中间表的外键列的名称

　　2、为了不重复更新，在其中的一端设置 inverse="true"的属性

　　3、在查询时需要连接中间表

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原文地址：https://www.cnblogs.com/maocs/p/4920100.html