Hibernate继承映射

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继承映射

三种方式，继承关系映射到数据库的表中

A.继承关系层次一个表(Table per class hierarchy),这种方式使用一个表存储同一个继承层次的所有类，使用额外的字段来表示所记录的是哪一个子类的数据

B.每个具体类一个表(Table per concrete class)，这种方式让继承关系中的每个具体类对应一个表

C.每个子类一个表(Table per subclass)，这种方式让继承关系中的父类分别对应一个表，父类与子类对应的表通过外键产生关系

详细介绍这三种方式的用法：

A. 1.一张同样的表:Delivery表

create table DELIVERY
(
ID              NUMBER not null,
RECIPIENT       VARCHAR2(200),
PHONE           VARCHAR2(200),
ADDRESS         VARCHAR2(400),
POSTCODE        VARCHAR2(10),
DELVERY_TYPE    VARCHAR2(20), //类型.如果值为POST则为POSTDelivery,如果是EXPRESS则为          //EXPRESSDelivery
PARCEL_NUMBER   VARCHAR2(30),
EXPRESS_NUMBER VARCHAR2(30),
EXPRESS_COMPANY VARCHAR2(40)
)

2.三个类，分别为: Delivery类/postDelivery/expressDelivery

Delivery.java

package com.util.deliery;

public class Delivery {

private int id;

private String recipient;

private String phone;

private String address;

private String postcode;

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getPhone() {

return phone;

}

public void setPhone(String phone) {

this.phone = phone;

}

public String getPostcode() {

return postcode;

}

public void setPostcode(String postcode) {

this.postcode = postcode;

}

public String getRecipient() {

return recipient;

}

public void setRecipient(String recipient) {

this.recipient = recipient;

}

PostDelivery.java

package com.util.deliery;

public class PostDelivery extends Delivery {

private String parceNumber;

public String getParceNumber() {

return parceNumber;

}

public void setParceNumber(String parceNumber) {

this.parceNumber = parceNumber;

}

ExpressDelivery.java

package com.util.deliery;

public class ExpressDelivery extends Delivery {

private String expressNumber;

private String expressCompany;

public String getExpressCompany() {

return expressCompany;

}

public void setExpressCompany(String expressCompany) {

this.expressCompany = expressCompany;

}

public String getExpressNumber() {

return expressNumber;

}

public void setExpressNumber(String expressNumber) {

this.expressNumber = expressNumber;

}

Delivery.hbm.xml配置文件：

<hibernate-mapping>

<class name="com.util.deliery.Delivery" table="DELIVERY"

schema="TEST">

</id>

<discriminator column="delivery_type"></discriminator> /*说明delivery_type 来区分是POST还是EXPRESS*/

</property>

</property>

</property>

</property>

/*配置POST专属的属性，若为delivery_type=”Post”则为PostDelivery */

<subclass name="com.util.deliery.PostDelivery"

discriminator-value="Post">

</property>

</subclass>

/*配置Express专属的属性，若为delivery_type=” Express”则为ExpressDelivery */

<subclass name="com.util.deliery.ExpressDelivery"

discriminator-value="Express">

</property>

</property>

</subclass>

</class>

</hibernate-mapping>

测试类：HibernateTest.java

public class HibernateTest {

/**

* @param args

public static void main(String[] args) {

new HibernateTest().insertDelivery();

new HibernateTest().listDelivery();

}

public void listDelivery() {

Session session = HibernateSessionFactory.getSessionFactory()

.getCurrentSession();

session.beginTransaction();

Query query = session.createQuery("form PostDelivery");

List<PostDelivery> list = query.list();

session.getTransaction().commit();

for (PostDelivery d : list) {

System.out.println(d.getRecipient());

System.out.print(d.getParcelNumber());

}

public void insertDelivery(){

PostDelivery post=new PostDelivery();

post.setRecipient("WO");

post.setAddress("NB");

post.setPhone("8856216");

post.setPostcode("315000");

post.setParcelNumber("8576");

ExpressDelivery express=new ExpressDelivery();

express.setRecipient("NI");

express.setAddress("NB");

express.setPhone("8856216");

express.setPostcode("315000");

express.setExpressCompany("NBWD");

express.setExpressNumber("5782");

Session session=HibernateSessionFactory.getSessionFactory().getCurrentSession();

session.beginTransaction();

session.save(post);

session.save(express);

session.getTransaction().commit();

}

A. 每个具体类一个表

Post_delivery 表：

字段id <pk> ,recipient,phone,address,postcode,parcel_number

Express_delivery表:

字段:id<pk>,recipient,phone,address,postcode,express_company,express_number

类Delivery(抽象类)

public abstract class Delivery implements java.io.Serializable{

private Integer id;

private String recipient;

private String phone;

private String address;

private String postcode;

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public String getPhone() {

return phone;

}

public void setPhone(String phone) {

this.phone = phone;

}

public String getPostcode() {

return postcode;

}

public void setPostcode(String postcode) {

this.postcode = postcode;

}

public String getRecipient() {

return recipient;

}

public void setRecipient(String recipient) {

this.recipient = recipient;

}

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

PostDelivery.java

public class PostDelivery extends Delivery {

private String parcelNumber;

public String getParcelNumber() {

return parcelNumber;

}

public void setParcelNumber(String parcelNumber) {

this.parcelNumber = parcelNumber;

}

ExpressDelivery.java

public class ExpressDelivery extends Delivery {

private String expressNumber;

private String expressCompany;

public String getExpressCompany() {

return expressCompany;

}

public void setExpressCompany(String expressCompany) {

this.expressCompany = expressCompany;

}

public String getExpressNumber() {

return expressNumber;

}

public void setExpressNumber(String expressNumber) {

this.expressNumber = expressNumber;

}

Delivery.hbm.xml

<hibernate-mapping>

<class name="com.util.deliery.Delivery" table="DELIVERY"

schema="TEST" abstract="true"> /*抽象类*/

</id>

</property>

</property>

</property>

</property>

/*对应的post_delivery表*/

<union-subclass name="com.util.deliery.PostDelivery" table="post_delivery">

</property>

</union-subclass>

/*对应的express_delivery表*/

<union-subclass name="com.util.deliery.ExpressDelivery" table="express_delivery">

</property>

</property>

</union-subclass>

</class>

</hibernate-mapping>

主鍵值:select max(ids_.id)

From (

Select

From

Post_delivery

Union

Select

From

Express_delivery

) ids_

效率比較低

A. 每个具体类一个表

Post_delivery 表：

字段id <pk> ,recipient,phone,address,postcode,parcel_number

Express_delivery表:

字段:id<pk>,recipient,phone,address,postcode,express_company,express_number

类Delivery(抽象类)

public abstract class Delivery implements java.io.Serializable{

private Integer id;

private String recipient;

private String phone;

private String address;

private String postcode;

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public String getPhone() {

return phone;

}

public void setPhone(String phone) {

this.phone = phone;

}

public String getPostcode() {

return postcode;

}

public void setPostcode(String postcode) {

this.postcode = postcode;

}

public String getRecipient() {

return recipient;

}

public void setRecipient(String recipient) {

this.recipient = recipient;

}

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

PostDelivery.java

public class PostDelivery extends Delivery {

private String parcelNumber;

public String getParcelNumber() {

return parcelNumber;

}

public void setParcelNumber(String parcelNumber) {

this.parcelNumber = parcelNumber;

}

ExpressDelivery.java

public class ExpressDelivery extends Delivery {

private String expressNumber;

private String expressCompany;

public String getExpressCompany() {

return expressCompany;

}

public void setExpressCompany(String expressCompany) {

this.expressCompany = expressCompany;

}

public String getExpressNumber() {

return expressNumber;

}

public void setExpressNumber(String expressNumber) {

this.expressNumber = expressNumber;

}

Delivery.hbm.xml

<hibernate-mapping>

<class name="com.util.deliery.Delivery" table="DELIVERY"

schema="TEST" abstract="true"> /*抽象类*/

</id>

</property>

</property>

</property>

</property>

/*对应的post_delivery表*/

<union-subclass name="com.util.deliery.PostDelivery" table="post_delivery">

</property>

</union-subclass>

/*对应的express_delivery表*/

<union-subclass name="com.util.deliery.ExpressDelivery" table="express_delivery">

</property>

</property>

</union-subclass>

</class>

</hibernate-mapping>

主鍵值:select max(ids_.id)

From (

Select

From

Post_delivery

Union

Select

From

Express_delivery

) ids_

效率比較低

B. 每個類一個表

Delivery表:

字段:id<pk>,pecipient,phone,address,postcode

Post_delivery表:

字段:id<pk,fk>,parcel_number

Express_delivery表:

字段:id<pk,fk>,expresscompany,expressnumber

2.三个类，分别为: Delivery类/postDelivery/expressDelivery

Delivery.java

package com.util.deliery;

public class Delivery {

private int id;

private String recipient;

private String phone;

private String address;

private String postcode;

public String getAddress() {

return address;

}

public void setAddress(String address) {

this.address = address;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getPhone() {

return phone;

}

public void setPhone(String phone) {

this.phone = phone;

}

public String getPostcode() {

return postcode;

}

public void setPostcode(String postcode) {

this.postcode = postcode;

}

public String getRecipient() {

return recipient;

}

public void setRecipient(String recipient) {

this.recipient = recipient;

}

PostDelivery.java

package com.util.deliery;

public class PostDelivery extends Delivery {

private String parceNumber;

public String getParceNumber() {

return parceNumber;

}

public void setParceNumber(String parceNumber) {

this.parceNumber = parceNumber;

}

ExpressDelivery.java

package com.util.deliery;

public class ExpressDelivery extends Delivery {

private String expressNumber;

private String expressCompany;

public String getExpressCompany() {

return expressCompany;

}

public void setExpressCompany(String expressCompany) {

this.expressCompany = expressCompany;

}

public String getExpressNumber() {

return expressNumber;

}

public void setExpressNumber(String expressNumber) {

this.expressNumber = expressNumber;

}

Delivery.hbm.xml

<hibernate-mapping>

<class name="com.util.deliery.Delivery" table="DELIVERY"

schema="TEST">

</id>

</property>

</property>

</property>

</property>

<joined-subclass name="com.util.deliery.PostDelivery" table="post_delivery">

</property>

</joined-subclass>

<joined-subclass name="com.util.deliery.ExpressDelivery" table="express_delivery">

</property>

</property>

</joined-subclass>

</class>

</hibernate-mapping>

內連接查詢：

Select postdelive0_id as id0_,

postdelive0_1_.recipient as recipient0_,

...

From post_delivery postdelive0_

Inner join

Delivery postdelive0_1_ on postdelivery0_.id=postdelive0_1.id