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hibernate3學習筆記(十五)｜繼承映射

編輯：關於JAVA

這裡詳細討論繼承映射的3種方式：

1.Table per concrete class

繼承關系如下圖：

數據表設計如下圖：

MySQL數據庫中執行如下DDL：

1.CREATE TABLE defaultuser (
2.    id INT(11) NOT NULL auto_increment PRIMARY KEY,
3.    name VARCHAR(100) NOT NULL default '',
4.    someProperty VARCHAR(100)
5.);
6.
7.CREATE TABLE poweruser (
8.    id INT(11) NOT NULL auto_increment PRIMARY KEY,
9.    name VARCHAR(100) NOT NULL default '',
10.    otherProperty VARCHAR(100)
11.);

User.java

1.package com.hb3.pack_08.model;
2.
3.public class User {
4.
5.    private Integer id;
6.    private String name;
7.
8.    public User() {
9.    }
10.
11.    public Integer getId() {
12.        return id;
13.    }
14.    public void setId(Integer id) {
15.        this.id = id;
16.    }
17.    public String getName() {
18.        return name;
19.    }
20.    public void setName(String name) {
21.        this.name = name;
22.    }
23.}

DefaultUser.java

1.package com.hb3.pack_08.model;
2.
3.public class DefaultUser extends User {
4.
5.    private String someProperty;
6.
7.    public DefaultUser() {
8.    }
9.
10.    public String getSomeProperty() {
11.        return someProperty;
12.    }
13.    public void setSomeProperty(String someProperty) {
14.        this.someProperty = someProperty;
15.    }
16.}

PowerUser.java

1.package com.hb3.pack_08.model;
2.
3.public class PowerUser extends User {
4.
5.    private String otherProperty;
6.
7.    public PowerUser() {
8.    }
9.
10.    public String getOtherProperty() {
11.        return otherProperty;
12.    }
13.    public void setOtherProperty(String otherProperty) {
14.        this.otherProperty = otherProperty;
15.    }
16.}

DefaultUser.hbm.xml文件：

1.<?xml version="1.0" encoding="UTF-8"?>
2.
3.<!DOCTYPE hibernate-mapping PUBLIC
4.    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
5.    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
6.
7.<hibernate-mapping>
8.
9.    <class name="com.hb3.pack_08.model.DefaultUser" table="defaultuser">
10.
11.        <id name="id" column="id" type="java.lang.Integer">
12.            <generator class="native"/>
13.        </id>
14.
15.        <property name="name" column="name" type="java.lang.String"/>
16.
17.        <property name="someProperty" column="someProperty" type="java.lang.String"/>
18.
19.    </class>
20.
21.</hibernate-mapping>

PowerUser.hbm.xml文件：

1.<?xml version="1.0" encoding="UTF-8"?>
2.
3.<!DOCTYPE hibernate-mapping PUBLIC
4.    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
5.    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
6.
7.<hibernate-mapping>
8.
9.    <class name="com.hb3.pack_08.model.PowerUser" table="poweruser">
10.
11.        <id name="id" column="id" type="java.lang.Integer">
12.            <generator class="native"/>
13.        </id>
14.
15.        <property name="name" column="name" type="java.lang.String"/>
16.
17.        <property name="otherProperty" column="otherProperty" type="java.lang.String"/>
18.
19.    </class>
20.
21.</hibernate-mapping>

修改hibernate.cfg.xml文件：

......

<mapping resource="com/hb3/pack_08/model/DefaultUser.hbm.xml" />
<mapping resource="com/hb3/pack_08/model/PowerUser.hbm.xml" />
......

1.package com.hb3.pack_08;
2.
3.import java.io.IOException;
4.import java.sql.SQLException;
5.import java.util.Iterator;
6.
7.import org.hibernate.Query;
8.import org.hibernate.Session;
9.import org.hibernate.SessionFactory;
10.import org.hibernate.Transaction;
11.import org.hibernate.cfg.Configuration;
12.

13.import com.hb3.pack_08.model.DefaultUser;
14.import com.hb3.pack_08.model.PowerUser;
15.import com.hb3.pack_08.model.User;
16.
17.public class BusinessService {
18.
19. public static void main(String[] args) throws IOException, SQLException {
20.
21. Configuration config = new Configuration().configure();
22. SessionFactory sessionFactory = config.buildSessionFactory();
23. Session session = sessionFactory.openSession();
24.
25.
26. DefaultUser defaultUser = new DefaultUser();
27. defaultUser.setName("chenyan");
28. defaultUser.setSomeProperty("hu....hu...");
29.
30. PowerUser powerUser = new PowerUser();
31. powerUser.setName("shenbin");
32. powerUser.setOtherProperty("Bla...Bla...");
33.
34. Transaction tx = session.beginTransaction();
35. session.save(powerUser);
36. session.save(defaultUser);
37. tx.commit();
38.
39.
40. session.close();
41. session = sessionFactory.openSession();
42.
43.
44. Query query = session.createQuery("from com.hb3.pack_08.model.User");
45. Iterator<?> iterator = query.list().iterator();
46. while(iterator.hasNext()) {
47. User user = (User) iterator.next();
48. System.out.println(user.getName());
49. }
50.
51.
52. session.close();
53. sessionFactory.close();
54. }
55.}

請注意：查詢中查詢的是User，所以會找出所有DefaultUser和PowerUser的資料。User類中不包括的他子類特有的字段也會被找到。

值得一提的是，查詢中如果直接使用"from java.lang.Object"這樣的HQL的話，將查出數據庫中所有的數據資料。因為Object是Java中所有類的父類。

2.Table per class hierarchy

數據表設計如下圖：

DDL文件：

1.CREATE TABLE user (
2.    id INT(11) NOT NULL auto_increment PRIMARY KEY,
3.    userType VARCHAR(50) NOT NULL,
4.    name VARCHAR(100) NOT NULL default '',
5.    someProperty VARCHAR(100),
6.    otherProperty VARCHAR(100)
7.);

POJO同上，分為：User，PowerUser，DefaultUser。

User.hbm.xml文件：

1.<?xml version="1.0" encoding="utf-8"?>
2.<!DOCTYPE hibernate-mapping 
3.    PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4.    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
5.
6.<hibernate-mapping>
7.
8.    <class name="com.hb3.pack_09.model.User" table="user">
9.
10.        <id name="id" column="id" type="java.lang.Integer">
11.            <generator class="native"/>
12.        </id>
13.
14.        <discriminator column="userType" type="java.lang.String"/>
15.
16.        <property name="name" column="name" type="java.lang.String"/>
17.
18.        <subclass name="com.hb3.pack_09.model.DefaultUser"
19.                  discriminator-value="Default">
20.
21.            <property name="someProperty"
22.                      column="someProperty"
23.                      type="java.lang.String"/>
24.        </subclass>
25.
26.        <subclass name="com.hb3.pack_09.model.PowerUser"
27.                  discriminator-value="Power">
28.
29.            <property name="otherProperty"
30.                      column="otherProperty"
31.                      type="java.lang.String"/>
32.        </subclass>
33.
34.    </class>
35.
36.</hibernate-mapping>

修改hibernate.cfg.xml文件：

...... <mapping resource="com/hb3/pack_09/model/User.hbm.xml" /> ......

測試代碼也和上面的基本一致:

1.package com.hb3.pack_09;
2.
3.import java.io.IOException;
4.import java.sql.SQLException;
5.import java.util.Iterator;
6.
7.import org.hibernate.Query;
8.import org.hibernate.Session;
9.import org.hibernate.SessionFactory;
10.import org.hibernate.Transaction;
11.import org.hibernate.cfg.Configuration;
12.
13.import com.hb3.pack_09.model.DefaultUser;
14.import com.hb3.pack_09.model.PowerUser;
15.import com.hb3.pack_09.model.User;
16.
17.public class BusinessService {
18.
19.    public static void main(String[] args) throws IOException, SQLException {
20.
21.        Configuration config = new Configuration().configure();
22.        SessionFactory sessionFactory = config.buildSessionFactory();
23.        Session session = sessionFactory.openSession();
24.
25.
26.        DefaultUser defaultUser = new DefaultUser();
27.        defaultUser.setName("chenyan");
28.        defaultUser.setSomeProperty("hu....hu...");
29.
30.        PowerUser powerUser = new PowerUser();
31.        powerUser.setName("shenbin");
32.        powerUser.setOtherProperty("Bla...Bla...");
33.
34.        Transaction tx = session.beginTransaction();
35.        session.save(powerUser);
36.        session.save(defaultUser);
37.        tx.commit();
38.
39.
40.        session.close();
41.        session = sessionFactory.openSession();
42.
43.
44.        Query query = session.createQuery("from com.hb3.pack_09.model.User");
45.        Iterator<?> iterator = query.list().iterator();
46.        while(iterator.hasNext()) {
47.                User user = (User) iterator.next();
48.                System.out.println(user.getName());
49.        }
50.
51.
52.        session.close();
53.        sessionFactory.close();
54.    }
55.}

3.Table per subclass

數據表設計如下圖：

DDL文件：

1.CREATE TABLE user (
2.    id INT(11) NOT NULL auto_increment PRIMARY KEY,
3.    name VARCHAR(100) NOT NULL default ''
4.);
5.
6.CREATE TABLE defaultuser (
7.    id INT(11) NOT NULL PRIMARY KEY,
8.    someProperty VARCHAR(100)
9.);
10.
11.CREATE TABLE poweruser (
12.    id INT(11) NOT NULL PRIMARY KEY,
13.    otherProperty VARCHAR(100)
14.);

POJO同上，分為：User，PowerUser，DefaultUser。

User.hbm.xml文件：

1.<?xml version="1.0" encoding="utf-8"?>
2.<!DOCTYPE hibernate-mapping 
3.    PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
4.    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
5.
6.<hibernate-mapping>
7.
8.    <class name="com.hb3.pack_10.model.User" table="user">
9.
10.        <id name="id" column="id" type="java.lang.Integer">
11.            <generator class="native"/>
12.        </id>
13.
14.        <property name="name" column="name" type="java.lang.String"/>
15.
16.        <joined-subclass name="com.hb3.pack_10.model.DefaultUser"
17.                         table="defaultuser">
18.
19.            <key column="id"/>
20.
21.            <property name="someProperty"
22.                      column="someProperty"
23.                      type="java.lang.String"/>
24.
25.        </joined-subclass>
26.
27.        <joined-subclass name="com.hb3.pack_10.model.PowerUser"
28.                         table="poweruser">
29.
30.            <key column="id"/>
31.
32.            <property name="otherProperty"
33.                      column="otherProperty"
34.                      type="java.lang.String"/>
35.
36.        </joined-subclass>
37.
38.    </class>
39.
40.</hibernate-mapping>

修改hibernate.cfg.xml文件：

...... <mapping resource="com/hb3/pack_10/model/User.hbm.xml" /> ......

測試代碼如下：

1.package com.hb3.pack_10;
2.
3.import java.io.IOException;
4.import java.sql.SQLException;
5.import java.util.Iterator;
6.
7.import org.hibernate.Query;
8.import org.hibernate.Session;
9.import org.hibernate.SessionFactory;
10.import org.hibernate.Transaction;
11.import org.hibernate.cfg.Configuration;
12.
13.import com.hb3.pack_10.model.DefaultUser;
14.import com.hb3.pack_10.model.PowerUser;
15.import com.hb3.pack_10.model.User;
16.
17.public class BusinessService {
18.
19.    public static void main(String[] args) throws IOException, SQLException {
20.
21.        Configuration config = new Configuration().configure();
22.        SessionFactory sessionFactory = config.buildSessionFactory();
23.        Session session = sessionFactory.openSession();
24.
25.
26.        DefaultUser defaultUser = new DefaultUser();
27.        defaultUser.setName("chenyan");
28.        defaultUser.setSomeProperty("hu....hu...");
29.
30.        PowerUser powerUser = new PowerUser();
31.        powerUser.setName("shenbin");
32.        powerUser.setOtherProperty("Bla...Bla...");
33.
34.        Transaction tx = session.beginTransaction();
35.        session.save(powerUser);
36.        session.save(defaultUser);
37.        tx.commit();
38.
39.
40.        session.close();
41.        session = sessionFactory.openSession();
42.
43.
44.        Query query = session.createQuery("from com.hb3.pack_10.model.User");
45.        Iterator<?> iterator = query.list().iterator();
46.        while(iterator.hasNext()) {
47.                User user = (User) iterator.next();
48.                System.out.println(user.getName());
49.        }
50.
51.
52.        session.close();
53.        sessionFactory.close();
54.    }
55.}