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 [Hibernate]hibernate一对多例子-已更新(二)
软件技术
lhwork 发表于 2007/1/7 14:04:29 |
| 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:
一个被包含的实体的实例只能被包含在一个集合的实例中
一个被包含的实体的实例只能对应于集合索引的一个值中
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.html1 先建表
500)this.width=500'>
create
table
student500)this.width=500'>(sid
varchar
(
32
)
not
null
primary
key
,500)this.width=500'> sname
varchar
(
16
),500)this.width=500'> sage
varchar
(
16
),500)this.width=500'>)500)this.width=500'>
create
table
book500)this.width=500'>(bid
varchar
(
32
)
not
null
primary
key
,500)this.width=500'>bname
varchar
(
16
),500)this.width=500'>bprice
varchar
(
16
),500)this.width=500'>sid
varchar
(
32
)500)this.width=500'>)500)this.width=500'>
2.写vo Student.java500)this.width=500'>package com.test;500)this.width=500'>500)this.width=500'>import java.util.Set;500)this.width=500'>500)this.width=500'>public class Student500)this.width=500'>500)this.width=500'>500)this.width=500'>{500)this.width=500'> private String sid;500)this.width=500'> private String sname;500)this.width=500'> private String sage;500)this.width=500'> private Set book;500)this.width=500'> public Student()500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> }500)this.width=500'> // 写上get setBook.JAVA500)this.width=500'>package com.test;500)this.width=500'>500)this.width=500'>public class Book500)this.width=500'>500)this.width=500'>500)this.width=500'>{500)this.width=500'> private String bid;500)this.width=500'> private String bname;500)this.width=500'> private String bprice;500)this.width=500'> public Book()500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> }500)this.width=500'> //写上get set3.写对应的映射文件Student.hbm.xml500)this.width=500'><?xml version="1.0"?>500)this.width=500'><!DOCTYPE hibernate-mapping500)this.width=500'> PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"500)this.width=500'> "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">500)this.width=500'>500)this.width=500'><hibernate-mapping>500)this.width=500'>500)this.width=500'> <class name="com.test.Student" table="student" >500)this.width=500'>500)this.width=500'> <id name="sid" type="string" unsaved-value="null" >500)this.width=500'> <column name="sid" sql-type="char(32)" not-null="true"/>500)this.width=500'> <generator class="uuid.hex"/>500)this.width=500'> </id>500)this.width=500'>500)this.width=500'> <property name="sname">500)this.width=500'> <column name="sname" sql-type="varchar(16)" not-null="true"/>500)this.width=500'> </property>500)this.width=500'>500)this.width=500'> <property name="sage">500)this.width=500'> <column name="sage" sql-type="varchar(16)" not-null="true"/>500)this.width=500'> </property>500)this.width=500'>500)this.width=500'> <set name="book" cascade="all" outer-join="true">500)this.width=500'> <key column="sid"/>500)this.width=500'> <one-to-many class="com.test.Book" />500)this.width=500'> </set>500)this.width=500'>500)this.width=500'> </class>500)this.width=500'>500)this.width=500'></hibernate-mapping>Book.hbm.xml500)this.width=500'><?xml version="1.0"?>500)this.width=500'><!DOCTYPE hibernate-mapping500)this.width=500'> PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"500)this.width=500'> "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">500)this.width=500'>500)this.width=500'><hibernate-mapping>500)this.width=500'>500)this.width=500'> <class name="com.test.Book" table="book" >500)this.width=500'>500)this.width=500'> <id name="bid" type="string" unsaved-value="null" >500)this.width=500'> <column name="bid" sql-type="char(32)" not-null="true"/>500)this.width=500'> <generator class="uuid.hex"/>500)this.width=500'> </id>500)this.width=500'>500)this.width=500'> <property name="bname">500)this.width=500'> <column name="bname" sql-type="varchar(16)" not-null="true"/>500)this.width=500'> </property>500)this.width=500'>500)this.width=500'> <property name="bprice">500)this.width=500'> <column name="bprice" sql-type="varchar(16)" not-null="true"/>500)this.width=500'> </property>500)this.width=500'>500)this.width=500'> </class>500)this.width=500'>500)this.width=500'></hibernate-mapping>接着把下面的hibernate.properties文件拷到classes目录下。。这里用的是mysql500)this.width=500'>hibernate.query.substitutions true 1, false 0, yes 'Y', no 'N'500)this.width=500'>## MySQL500)this.width=500'>hibernate.dialect net.sf.hibernate.dialect.MySQLDialect500)this.width=500'>hibernate.connection.driver_class org.gjt.mm.mysql.Driver500)this.width=500'>hibernate.connection.url jdbc:mysql://localhost:3306/wjcms500)this.width=500'>hibernate.connection.username root500)this.width=500'>hibernate.connection.password wujun500)this.width=500'>hibernate.connection.pool_size 1500)this.width=500'>hibernate.proxool.pool_alias pool1500)this.width=500'>hibernate.show_sql true500)this.width=500'>hibernate.jdbc.batch_size 0500)this.width=500'>hibernate.max_fetch_depth 1500)this.width=500'>hibernate.cache.use_query_cache true 4.写测试类了..500)this.width=500'>package com.test;500)this.width=500'>500)this.width=500'>import net.sf.hibernate.Session;500)this.width=500'>import net.sf.hibernate.SessionFactory;500)this.width=500'>import net.sf.hibernate.cfg.Configuration;500)this.width=500'>import net.sf.hibernate.*;500)this.width=500'>import java.util.Set;500)this.width=500'>import java.util.HashSet;500)this.width=500'>import java.sql.*;500)this.width=500'>import java.util.List;500)this.width=500'>import java.util.Iterator;500)this.width=500'>500)this.width=500'>public class TestOneToMany500)this.width=500'>500)this.width=500'>500)this.width=500'>{500)this.width=500'> SessionFactory sf;500)this.width=500'> Session session;500)this.width=500'> public TestOneToMany()500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> try500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> Configuration cfg = new Configuration();500)this.width=500'> sf = cfg.addClass(Student.class).addClass(Book.class).buildSessionFactory();500)this.width=500'> }500)this.width=500'> catch(HibernateException ex)500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> ex.printStackTrace();500)this.width=500'> }500)this.width=500'> }500)this.width=500'> //插入500)this.width=500'> public void doCreate()500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> try500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> session = sf.openSession();500)this.width=500'>500)this.width=500'> Student student = new Student();500)this.width=500'> student.setSname("小王");500)this.width=500'> student.setSage("22");500)this.width=500'>500)this.width=500'> Set bookSet = new HashSet();500)this.width=500'> Book book = null;500)this.width=500'> for(int i=0;i<2;i++)500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> book = new Book();500)this.width=500'> book.setBname("java "+i);500)this.width=500'> book.setBprice("50");500)this.width=500'> bookSet.add(book);500)this.width=500'> }500)this.width=500'> student.setBook(bookSet);500)this.width=500'>500)this.width=500'> session.save(student);500)this.width=500'> session.flush();500)this.width=500'> session.connection().commit();500)this.width=500'>500)this.width=500'> }500)this.width=500'> catch(HibernateException ex)500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> ex.printStackTrace();500)this.width=500'> }500)this.width=500'> catch(SQLException ex1)500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> ex1.printStackTrace();500)this.width=500'> }500)this.width=500'> finally500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'>500)this.width=500'> try500)this.width=500'>{500)this.width=500'> session.close();500)this.width=500'> }500)this.width=500'>500)this.width=500'> catch(HibernateException ex2)500)this.width=500'>{500)this.width=500'> }500)this.width=500'> }500)this.width=500'>500)this.width=500'> }500)this.width=500'> //查询500)this.width=500'> public void doQuery()500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'>500)this.width=500'> try500)this.width=500'>{500)this.width=500'> session = sf.openSession();500)this.width=500'> Query q = session.createQuery("select s from Student as s");500)this.width=500'> List l = q.list();500)this.width=500'> Student s = null;500)this.width=500'> Book book = null;500)this.width=500'> for(int i=0;i<l.size();i++)500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> s = (Student)l.get(i);500)this.width=500'> System.out.println("姓名： "+s.getSname());500)this.width=500'> System.out.println("年龄： "+s.getSage());500)this.width=500'> System.out.println("所有的书：");500)this.width=500'> Iterator it = s.getBook().iterator();500)this.width=500'> while(it.hasNext())500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> book = (Book)it.next();500)this.width=500'> System.out.println("书名： "+book.getBname());500)this.width=500'> System.out.println("价格： "+book.getBprice());500)this.width=500'> }500)this.width=500'>500)this.width=500'>500)this.width=500'> }500)this.width=500'>500)this.width=500'> }500)this.width=500'>500)this.width=500'> catch(HibernateException ex)500)this.width=500'>{500)this.width=500'> ex.printStackTrace();500)this.width=500'> }500)this.width=500'>500)this.width=500'> finally500)this.width=500'>{500)this.width=500'>500)this.width=500'> try500)this.width=500'>{500)this.width=500'> session.close();500)this.width=500'> }500)this.width=500'>500)this.width=500'> catch(HibernateException ex2)500)this.width=500'>{500)this.width=500'> }500)this.width=500'> }500)this.width=500'> }500)this.width=500'> public static void main(String[] args)500)this.width=500'>500)this.width=500'> 500)this.width=500'>{500)this.width=500'> TestOneToMany t = new TestOneToMany();500)this.width=500'> //t.doCreate();500)this.width=500'> t.doQuery();500)this.width=500'> }500)this.width=500'>}500)this.width=500'>好了。。 |
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