Hibernate 3.2 学习笔记映射集合类

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映射值属性集合类
值属性集合类没有单独的OID和生命周期实体类集合有单独的OID和生命周期
set 不允许重复
属性:

name 指定集合的属性名

table 对应的表

lazy 延迟检索策略

                      inverese 有较好的update性能但是不会按照one方来同步更新数据库(要注意)
                      order-by   数据库排序方式
                      sort         内存排序方式

元素:

<key> 定义外键

<one-to-many> 定义many 方的类

注：由于采用了延时检索策略所以在读取的时候
用hibernate.isInitialized(Object)检查
用hibernate.initialize(java.lang.Object proxy) 来初始化集合

<set name="images" table="IMAGES"

inverse="false"

cascade="save-update"

lazy="true">

</set>

例子
Customer.hbm.xm

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

<set name="images" table="IMAGES"

inverse="false"

cascade="save-update"

lazy="true">

</set>

</class>

</hibernate-mapping>

运行hbm2ddl
两表
Customer
1 - ID
2 - NAME
3 - AGE
IMAGES
1 - CUSTOMER_ID
2 - FILENAME

测试代码
BusinessService.java

package ergal;

import java.util.*;

import org.hibernate.*;

import org.hibernate.cfg.*;

import java.sql.*;

public class BusinessService

{

public static SessionFactory sessionFactory;

static

{

try

{

Configuration config=new Configuration();

sessionFactory=config.configure().buildSessionFactory();

}

catch(Exception e)

{

e.printStackTrace();

}

public void saveCustomer(Object customer)throws Exception

{

Session session=sessionFactory.openSession();

Transaction tx=null;

try

{

tx=session.beginTransaction();

session.save(customer);

tx.commit();

}

catch(Exception e)

{

if(tx!=null)

{

tx.rollback();

}

throw e;

}

finally

{

session.close();

}

public Customer loadCustomer(Long id)throws Exception

{

Session session=sessionFactory.openSession();

Transaction tx=null;

try

{

tx=session.beginTransaction();

Customer customer=(Customer)session.load(Customer.class, id);

Hibernate.initialize(customer.getImages());

tx.commit();

return customer;

}

catch(Exception e)

{

if(tx!=null)

{

tx.rollback();

}

throw e;

}

finally

{

session.close();

}

public void test()throws Exception

{

Set images=new HashSet();

images.add("image1.jpg");

images.add("image4.jpg");

images.add("image2.jpg");

images.add("image5.jpg");

Customer customer = new Customer("Tom", 21, images);

saveCustomer(customer);

Customer c=loadCustomer(new Long(1));

System.out.println(customer.getImages().getClass().getName());

Iterator it = customer.getImages().iterator();

while(it.hasNext())

{

String filename=(String)it.next();

System.out.println(customer.getName()+ " " + filename);

}

public static void main(String[] args)throws Exception

{

new BusinessService().test();

sessionFactory.close();

}

Bag 允许重复不能排序

属性:

name 指定集合的属性名

table 对应的表

lazy 延迟检索策略

//inverese 有较好的update性能但是不会按照one方来同步更新数据库(要注意)
order-by 数据库排序方式

             元素:
                     <collection-id name="" table="" lazy="">
                                   <generator class="native"/>
                     <collection-id/>

<key> 定义外键

//<one-to-many> 定义many 方的类

注：由于采用了延时检索策略所以在读取的时候
用hibernate.isInitialized(Object)检查
用hibernate.initialize(java.lang.Object proxy) 来初始化集合

<collection-id type="long" column="ID">

</collection-id>

</idbag>

例子
Customer.hbm.xml

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

<collection-id type="long" column="ID">

</collection-id>

</idbag>

</class>

</hibernate-mapping>

注：这里的collection-id 为increment 才能正常运行
运行hbm2ddl后产生两表
customers
1 - ID
2 - NAME
3 - AGE

IMAGES
1 - CUSTOMER_ID
2 - FILENAME
3 - ID

测试代码中
原来的
Set images=new HashSet();
改成
List images=new ArrayList();

也可以用java.util.Collection来代替List

注意：

虽然可以用List但是只要是idbag 集合中的元素就不会按照索引来排序
要排序用List映射

映射List 允许存放重复元素可以按照索引排序

属性:

name 指定集合的属性名

table 对应的表

lazy 延迟检索策略

inverese 有较好的update性能但是不会按照one方来同步更新数据库(要注意)

元素:

                     <key column=""> 定义外键
                     <index column=""> 设置代表索引的字段
                     //<one-to-many> 定义many 方的类

注：由于采用了延时检索策略所以在读取的时候
用hibernate.isInitialized(Object)检查
用hibernate.initialize(java.lang.Object proxy) 来初始化集合

</list>

例子
Customer.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

</list>

</class>

</hibernate-mapping>

测试代码

List images=new ArrayList();

images.add("image1.jpg");

images.add("image4.jpg");

images.add("image2.jpg");

images.add("image5.jpg");

Customer customer = new Customer("Tom", 21, images);

saveCustomer(customer);

Customer c=loadCustomer(new Long(1));

System.out.println(customer.getImages().getClass().getName());

List it = customer.getImages();

for(int i=0; i<=it.size()-1; i++)

{

String fileName=(String)it.get(i);

System.out.println(customer.getName()+" "+fileName);

}

注意：取得元素的方法是String fileName=(String)it.get(i);

显然这种方法是可以为索引排序的

map 每个元素包含一对键对象和值对象不会对键对象排序

属性:

name 指定集合的属性名

table 对应的表

lazy 延迟检索策略

                      //inverese 有较好的update性能但是不会按照one方来同步更新数据库(要注意)
                      order-by   数据库排序方式
                      sort         内存排序方式
             元素:

                     <key column=""> 定义外键
                     <index column="" type=""> 设置代表和键对象对应的字段
                     //<one-to-many> 定义many 方的类

注：由于采用了延时检索策略所以在读取的时候
用hibernate.isInitialized(Object)检查
用hibernate.initialize(java.lang.Object proxy) 来初始化集合

</map>

例子
Customer.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

</map>

</class>

</hibernate-mapping>

运行hbm2ddl后产生两表
customers
1 - ID
2 - NAME
3 - AGE

IMAGES
1 - CUSTOMER_ID
2 - FILENAME
3 - IMAGE_NAME

测试代码变成

Map images=new HashMap();

images.put("image1","image1.jpg");

images.put("image4","image4.jpg");

images.put("image2","image2.jpg");

images.put("imageTwo","image2.jpg");

images.put("image5","image5.jpg");

Customer customer = new Customer("Tom", 21, images);

saveCustomer(customer);

Customer c=loadCustomer(new Long(1));

System.out.println(customer.getImages().getClass().getName());

Map im = customer.getImages();

Set keys=im.keySet();

Iterator it=keys.iterator();

while(it.hasNext())

{

String keyname=(String)it.next();

String fileName=(String)im.get(keyname);

System.out.println(customer.getName()+" "+keyname+" "+fileName);

}

用了Map里的get(Object key) 和 keySet()方法
此方法不会对键对象排序

对集合排序

有两种方式：
在数据库中排序 order-by
在内存中排序 sort 体现在代码中原来的Set 变成了SortedSet 查询时可以用TreeSet

<set>和<map>两种都支持
<idbag>支持在内存中排序 sort
<list>两种都不支持
sort 在内存中排序
1 set
例子
Customer.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

<set name="images" table="IMAGES"

inverse="false"

cascade="save-update"

lazy="true"

sort="natural">

</set>

</class>

</hibernate-mapping>

Customer.java

package ergal;

// Generated 2006-8-30 5:27:45 by Hibernate Tools 3.2.0.beta7

import java.util.*;

/**

* Customer generated by hbm2java

public class Customer implements java.io.Serializable {

// Fields

private long id;

private String name;

private int age;

private Set images=new TreeSet();

// Constructors

/** default constructor */

public Customer() {

}

/** full constructor */

public Customer(String name, int age, Set images) {

this.name = name;

this.age = age;

this.images = images;

}

// Property accessors

public long getId() {

return this.id;

}

public void setId(long id) {

this.id = id;

}

public String getName() {

return this.name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return this.age;

}

public void setAge(int age) {

this.age = age;

}

public Set getImages() {

return this.images;

}

public void setImages(Set images) {

this.images = images;

}

测试代码

Set images=new TreeSet();

images.add("image1.jpg");

images.add("image4.jpg");

images.add("image2.jpg");

images.add("image5.jpg");

Customer customer = new Customer("Tom", 21, images);

saveCustomer(customer);

Customer c=loadCustomer(new Long(1));

System.out.println(customer.getImages().getClass().getName());

Iterator it = customer.getImages().iterator();

while(it.hasNext())

{

String filename=(String)it.next();

System.out.println(customer.getName()+ " " + filename);

}

可以客户化排序方式要实现comparator接口

注意：可能需要手动修改POJO
images集合必须是SortedSet类型

2 map

Customer.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

</map>

</class>

</hibernate-mapping>

Customer.java

package ergal;

// Generated 2006-8-30 6:00:11 by Hibernate Tools 3.2.0.beta7

import java.util.*;

/**

* Customer generated by hbm2java

public class Customer implements java.io.Serializable {

// Fields

private long id;

private String name;

private int age;

private Map images=new TreeMap();

// Constructors

/** default constructor */

public Customer() {

}

/** full constructor */

public Customer(String name, int age, Map images) {

this.name = name;

this.age = age;

this.images = images;

}

// Property accessors

public long getId() {

return this.id;

}

public void setId(long id) {

this.id = id;

}

public String getName() {

return this.name;

}

public void setName(String name) {

this.name = name;

}

public int getAge() {

return this.age;

}

public void setAge(int age) {

this.age = age;

}

public Map getImages() {

return this.images;

}

public void setImages(Map images) {

this.images = images;

}

注意：可能需要手动修改POJO
images集合必须是SortedMap类型

order-by 在数据库中排序

只需在元素里加上 order-by属性
如

<set name="images" table="IMAGES"

inverse="false"

cascade="save-update"

lazy="true"

order-by="FILENAME asc">

</set>

也可以加上sql函数
如 order-by="lower(FILENAME) asc"

映射组件集合

组件也是一种值对象

它必须实现java.io.Serializable接口

它必须重新实现equals()和hashCode()方法, 始终和组合关键字在数据库中的概念保持一致

例子
Customer.hbm.xml

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC

"-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

</id>

<composite-element class="ergal.Image">

</composite-element>

</set>

</class>

</hibernate-mapping>

Image.java
需要手动添加 Customer 字段
parent不能用hbm2java来自动产生不知道这是不是个Bug

package ergal;

// Generated 2006-8-30 20:35:11 by Hibernate Tools 3.2.0.beta7

/**

* Image generated by hbm2java

public class Image implements java.io.Serializable {

// Fields

private String name;

private String filename;

private Integer sizeX;

private Integer sizeY;

private Customer imageCustomer;

// Constructors

/** default constructor */

public Image() {

}

/** full constructor */

public Image(String name, String filename, Integer sizeX, Integer sizeY) {

this.name = name;

this.filename = filename;

this.sizeX = sizeX;

this.sizeY = sizeY;

}

// Property accessors

public String getName() {

return this.name;

}

public void setName(String name) {

this.name = name;

}

public String getFilename() {

return this.filename;

}

public void setFilename(String filename) {

this.filename = filename;

}

public Integer getSizeX() {

return this.sizeX;

}

public void setSizeX(Integer sizeX) {

this.sizeX = sizeX;

}

public Integer getSizeY() {

return this.sizeY;

}

public void setSizeY(Integer sizeY) {

this.sizeY = sizeY;

}

public Customer getImageCustomer()

{

return this.imageCustomer;

}

public void setImageCustomer(Customer imageCustomer)

{

this.imageCustomer=imageCustomer;

}

测试代码

Set images=new HashSet();

images.add(new Image("image1","image1.jpg",50,50));

images.add(new Image("image4","image4.jpg",50,50));

images.add(new Image("image2","image2.jpg",50,50));

images.add(new Image("image5","image5.jpg",50,50));

Customer customer = new Customer("Tom", 21, images);

saveCustomer(customer);

Customer c=loadCustomer(new Long(1));

System.out.println(customer.getImages().getClass().getName());

Iterator it = customer.getImages().iterator();

while(it.hasNext())

{

Image im=(Image)it.next();

System.out.println(c.getName()+" "+im.getName()

+" "+im.getFilename()+" "+im.getSizeX()+" "+im.getSizeY());

}

Hibernate 3.2 学习笔记 映射集合类

Hibernate 3.2 学习笔记映射集合类