Hibernate mapping summarize

总结了Hibernate中实体对象与数据的映射方式……图文并茂，配置实例代码，为david吃饱了撑着之大作。

1 Entity's relation

1.1 One to One

一个对象的一个实例对应另一个对象的一个实例从数据库角度描述，一个表中的一条记录对应另外一个表中唯一一条记录

public class Image{
private Long id;
private String imgName;
private Blog value; //to store binary of image
......
}
Image.hbm.xml
<class name="Image" dynamic-update="true">
<id...
<property...
</class>

public class Product{
private Long id;
private String name;
private double price;
private Image photo;
}
<class name=...dynamic-update="true" lazy="true"
<id...
<property...
<one-to-one name="photo" class="package.Image" cascade="all" outer-join="auto" constrained="false"/>
</class>

1.2 Many to One

一个对象对应另一个对象的多个实例，从数据库角度描述，是在一个数据表中的一条记录对应另外一个数据表中对条记录.

public class PersonalCompute{
private Long computerId;
private String cpu;
......
private Programmer owner;
}
<class name="Programmer" table="Programmer">
<id...
<property...
</class>

<class name="PersonalCompute" table="PCS">
<id....
<property...
<many-to-one name="owner" column="programmerId" class="Programmer">
</many-to-one>

1.3 One to Many

The same example as Many to One.But we stand at Programmer class's view point.
public class Programmer{
...
private Set computers = new HashSet();
}

2 Collection

2.1 Map

showcase:
Team team1 = new Team();
team1.setName(xx);
team1.getMembers.put("index","content");
......
sess.save...

2.1.1 many-to-any

2.1.2 One to many

单单使用Map做存储往往无法表达复杂的对象,如果要讲对象 map进行映射:
One Team,multi-members
Public class Member{
...
private Team team;
}
<class name="Team">
...
<map name="members" inverse="false">
<key column="team" foreign-key="fk"/>
<index type="string" column="teamRole"/>
<one-to-many class="Member"/>
</map>
<class name="member">
<id...
<property...
<many-to-one name="team" />

showcase:
Team team = new Team();
team.setName("xx");
Member mem1 = new Member();
mem1.setXX
mem1.setXX
Member mem2 = new Member();
mem2.setXX
mem2.setXX
team.getMembers().put("xx",mem1);
team.getMembers().put("xx2",mem2);

2.1.3 many to many

<class name="Member">
<id
<property
<map name="teams" table="memberAtTeams">
<key....

teamRole is their common key of Map.
Team

id	name
2	team2

Member

di	name	age
1	davy	23

memberAtTeams

member	team	teamRole
1	2	coach

teamHasMembers

team	member	teamRole
2	1	coach

2.1.4 Composite-index

复杂Index 可以是一个类。
public class Position{
private String role;
private String scene;
public Position()....
getter...
setter...
}
<class name="Team">
<id...
<property...
<map name="members" inverse="false">
<key column="team" foreign-key="fk"/>
<composite-index class="Position">
<key-property..
<key-property...
</composite-index>
<one-to-many class="Member"/>
</map>
...

<class name="Member">
<id...
<property...
<many-to-one name="team"/>
</class>

index-many-to-one

index-many-to-many

index-many-to-any

2.1.5 composite-element

2.2 Set

2.2.1 one-to-many

2.2.2 many-to-many

2.2.3 many-to-any

2.2.4 composite-element

2.3 List

2.3.1 one-to-many

2.3.2 many-to-many

2.3.3 many-to-many

2.3.4 composite-element

2.4 Bag

It can contains JDK's Collection and List interface type's object.

2.5 idBag

与bag相比多出了collection-id属性

2.6 array

public class Team{
//...
private String[] members;
}

3 Component

<class name="Country">
<id..
<property...
<component name="position">
<property...
</component>
Public class Country{
//..
private Position position;
}

3.1 One-to-one

3.2 many-to-one

3.3 dynamic-component

4 Dynamic class

<dynamic-class entity-name="Country">
<id name="id" type="long">
<generator class=" hilo "/>
</id>
<property name="name" column="NAME" type="string"/>
</..

4.1 One-to-one

4.2 many-to-one

5 Mapping type

5.1 Java type to SQL type

5.2 3.0 enmu

5.3 user defined data type

need implements org.hibernate.usertype.CompositeUserType or org.hibernate.usertype.UserType interface.

6 Class Hierarchy's mapping

6.1 Subclasses are saved in on Table

6.1.1 discriminator

Sapmle:

Class AbstractParent{
String id;
/*important*/
String discriminator
}
Class ChildA{
String childA;
}
Class ChildB{
String childB;
}

=========DB=========

colum name	data type	memo
id	varchar
childA	varchar
childB	varchar
class_type	varchar	used to identify subclass:A B

========mapping config file====
<class name="AbstractParent" table="PARENT" abstract="true">
<id...
<discriminator column="CLASS_TYPE" type="string"/>
<property......
<subclass name="ChildA" discriminator-value="A">
<property name="childA"/>
</subclass>
<subclass......

id generator

· increment

· identity

· sequence

· hilo

· seqhilo

· uuid

· guid

· native

· assigned

· foreign

composite id

<composite-id>
<key-property name=""/>
<key-property name=""/>
</composite-id>

6.2 Subclasses are saved in separated Table

并不为父类Container建立映射文件 Box与Bottle的映射文件也如没有关系一样普通的建立但是对Container取得操作

List pcs = sess.createQuery("from com.be.david.Container").list();
if(!cs.isEmpty()){
...
}
会将Box与Container数据都取出来这是Hibernate默认隐式完成的

6.3 Parent Class and Subclasses are saved in separated Table

6.4 One PO multi-table

public Class Person{
牋牋燬tring id;
牋牋燬tring name;
牋牋燬tring sex;
牋牋燬tring address;
牋牋燬tring city;
牋牋燬tring zipcode;
}
we wanna save address related attributes(blue ones).Use join
<class name="Person" table="PERSON">
<id...
<property ...
<join table="ADDRESS">
牋 <key column="addressID"/>
牋 <property name="address"/>
牋 ...
牋 </join>
</class>

6.5 Class A Class B not inherited from Parent Class

6.5.1 subselect

We can use subselct to make ChildA and ChildB standalone.So how can we get all data including ChindA and ChildB?

<class name="ChildA" table="parent">
<id...
<property...
</class>
<class name="ChildB" table="parent">
<id...
<property...
</class>
<class name="Parent" mutable="false">
<subselect>
select * from ChildA
union
select * from ChildB
</subselect>
<sychronize table="ChildA"/>
<sychronize table="ChildB"/>
<id...
<property...
</class>

Hibernate mapping summarize

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