先看由满江红翻译团队(RedSaga Translate Team)翻译的一对多配置说明
然后在看例子
一对多关联（One-to-many Associations）
一对多关联
通过外键
连接两个类对应的表,而没有中间集合表。 这个关系模型失去了一些Java集合的语义:
一个从Product到Part的关联需要关键字字段,可能还有一个索引字段指向Part所对应的表。 <one-to-many>标记指明了一个一对多的关联。
<one-to-many
class="ClassName" (1)
not-found="ignore|exception" (2)
entity-name="EntityName" (3)
node="element-name"
embed-xml="true|false"
/>
| (1) |
class(必须):被关联类的名称。
|
| (2) |
not-found (可选 - 默认为exception): 指明若缓存的标示值关联的行缺失,该如何处理: ignore 会把缺失的行作为一个空关联处理。
|
| (3) |
entity-name (可选): 被关联的类的实体名，作为class的替代。
|
例子
<set name="bars">
<key column="foo_id"/>
<one-to-many class="org.hibernate.Bar"/>
</set>
注意:<one-to-many>元素不需要定义任何字段。 也不需要指定表名。
重要提示
:如果一对多关联中的外键字段定义成NOT NULL,你必须把<key>映射声明为not-null="true",或者使用双向关联，并且标明inverse="true"。
详细请看http://www.huihoo.com/framework/hibernate/reference-v3_zh-cn/collections.html
1 先建表
create
table
student
(sid
varchar
(
32
)
not
null
primary
key
,
sname
varchar
(
16
),
sage
varchar
(
16
),
)
create
table
book
(bid
varchar
(
32
)
not
null
primary
key
,
bname
varchar
(
16
),
bprice
varchar
(
16
),
sid
varchar
(
32
)
)
2.写vo
Student.java
package com.test;
import java.util.Set;
public class Student
{
private String sid;
private String sname;
private String sage;
private Set book;
public Student()
{
}
// 写上get set Book.JAVA
package com.test;
public class Book
{
private String bid;
private String bname;
private String bprice;
public Book()
{
}
//写上get set 3.写对应的映射文件
Student.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
<class name="com.test.Student" table="student" >
<id name="sid" type="string" unsaved-value="null" >
<column name="sid" sql-type="char(32)" not-null="true"/>
<generator class="uuid.hex"/>
</id>
<property name="sname">
<column name="sname" sql-type="varchar(16)" not-null="true"/>
</property>
<property name="sage">
<column name="sage" sql-type="varchar(16)" not-null="true"/>
</property>
<set name="book" cascade="all" outer-join="true">
<key column="sid"/>
<one-to-many class="com.test.Book" />
</set>
</class>
</hibernate-mapping> Book.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
<class name="com.test.Book" table="book" >
<id name="bid" type="string" unsaved-value="null" >
<column name="bid" sql-type="char(32)" not-null="true"/>
<generator class="uuid.hex"/>
</id>
<property name="bname">
<column name="bname" sql-type="varchar(16)" not-null="true"/>
</property>
<property name="bprice">
<column name="bprice" sql-type="varchar(16)" not-null="true"/>
</property>
</class>
</hibernate-mapping> 接着把下面的hibernate.properties文件拷到classes目录下。。这里用的是mysql
hibernate.query.substitutions true 1, false 0, yes 'Y', no 'N'
## MySQL
hibernate.dialect net.sf.hibernate.dialect.MySQLDialect
hibernate.connection.driver_class org.gjt.mm.mysql.Driver
hibernate.connection.url jdbc:mysql://localhost:3306/wjcms
hibernate.connection.username root
hibernate.connection.password wujun
hibernate.connection.pool_size 1
hibernate.proxool.pool_alias pool1
hibernate.show_sql true
hibernate.jdbc.batch_size 0
hibernate.max_fetch_depth 1
hibernate.cache.use_query_cache true 4.写测试类了..
package com.test;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.cfg.Configuration;
import net.sf.hibernate.*;
import java.util.Set;
import java.util.HashSet;
import java.sql.*;
import java.util.List;
import java.util.Iterator;
public class TestOneToMany
{
SessionFactory sf;
Session session;
public TestOneToMany()
{
try
{
Configuration cfg = new Configuration();
sf = cfg.addClass(Student.class).addClass(Book.class).buildSessionFactory();
}
catch(HibernateException ex)
{
ex.printStackTrace();
}
}
//插入
public void doCreate()
{
try
{
session = sf.openSession();
Student student = new Student();
student.setSname("小王");
student.setSage("22");
Set bookSet = new HashSet();
Book book = null;
for(int i=0;i<2;i++)
{
book = new Book();
book.setBname("java "+i);
book.setBprice("50");
bookSet.add(book);
}
student.setBook(bookSet);
session.save(student);
session.flush();
session.connection().commit();
}
catch(HibernateException ex)
{
ex.printStackTrace();
}
catch(SQLException ex1)
{
ex1.printStackTrace();
}
finally
{
try{
session.close();
}
catch(HibernateException ex2){
}
}
}
//查询
public void doQuery()
{
try{
session = sf.openSession();
Query q = session.createQuery("select s from Student as s");
List l = q.list();
Student s = null;
Book book = null;
for(int i=0;i<l.size();i++)
{
s = (Student)l.get(i);
System.out.println("姓名： "+s.getSname());
System.out.println("年龄： "+s.getSage());
System.out.println("所有的书：");
Iterator it = s.getBook().iterator();
while(it.hasNext())
{
book = (Book)it.next();
System.out.println("书名： "+book.getBname());
System.out.println("价格： "+book.getBprice());
}
}
}
catch(HibernateException ex){
ex.printStackTrace();
}
finally{
try{
session.close();
}
catch(HibernateException ex2){
}
}
}
public static void main(String[] args)
{
TestOneToMany t = new TestOneToMany();
//t.doCreate();
t.doQuery();
}
}
好了。。
在这里把这些例子几下来。。方便查阅。。
也是很适合象我们这样的出学者。。。