hibernate之多态关联(多态的多对一关联或者多态的一对一关联,利用union-subclass)

hibernate之多态关联(多态的多对一关联或者多态的一对一关联)
不必做任何特别的事情来启用hibernate中的多态关联，在关联映射中指定任何被映射的持久化类的名称，然后，如果该类声明了任何<union-subclass>,<subclass>或者<joined-subclass>元素，该关联就自然地成为多态。
下面以关联映射中映射的持久化类中声明了<union-subclass>为例：

pom.xml:

]<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>
<groupId>hibernateTest</groupId>
<artifactId>hibernateTest</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>jar</packaging>
<name>hibernateTest</name>
<url>http://maven.apache.org</url>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.3.1.GA</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.5.2</version>
</dependency>
<dependency>
<groupId>javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.4.GA</version>
</dependency>
<dependency>
<groupId>c3p0</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.1</version>
</dependency>
<dependency>
<groupId>com.oracle</groupId>
<artifactId>ojdbc14</artifactId>
<version>10.2.0.3.0</version>
<scope>runtime</scope>
</dependency>
</dependencies>
<build>
<finalName>hibernateTest</finalName>
<resources>
<resource>
<directory>src/main/resources</directory>
</resource>
<resource>
<directory>src/main/java</directory>
<excludes>
<exclude>**/*.java</exclude>
</excludes>
</resource>
</resources>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
<encoding>UTF-8</encoding>
</configuration>
</plugin>
</plugins>
</build>
</project>

resources/hibernate.cfg.xml:

]<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration
PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory name="sessionFactory">
<!-- 指定连接数据库所用的驱动 -->
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<!-- 指定连接数据库的url，hibernate连接的数据库名 -->
<property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:XE</property>
<property name="hibernate.connection.useUnicode">true</property>
<property name="hibernate.connection.characterEncoding">gbk</property>
<!-- 指定连接数据库的用户名 -->
<property name="hibernate.connection.username">system</property>
<!-- 指定连接数据库的密码 -->
<property name="hibernate.connection.password">password</property>
<!-- 指定连接池里最大连接数 -->
<property name="hibernate.c3p0.max_size">20</property>
<!-- 指定连接池里最小连接数 -->
<property name="hibernate.c3p0.min_size">5</property>
<!-- 指定连接池里连接的超时时长,以秒为单位 -->
<property name="hibernate.c3p0.timeout">120</property>
<!-- 指定连接池里最大缓存多少个Statement对象 -->
<property name="hibernate.c3p0.max_statements">100</property>
<!-- 每隔XX秒检查连接池里的空闲连接 ，单位是秒 -->
<property name="hibernate.c3p0.idle_test_period">120</property>
<!-- 当连接池里面的连接用完的时候，C3P0一次获取的新的连接数 -->
<property name="hibernate.c3p0.acquire_increment">2</property>
<!-- 指定数据库方言 -->
<property name="dialect">org.hibernate.dialect.OracleDialect</property>
<!-- 显示Hibernate持久化操作所生成的SQL -->
<property name="show_sql">true</property>
<!-- 将SQL脚本进行格式化后再输出 -->
<property name="hibernate.format_sql">true</property>
<!-- 罗列所有的映射文件 -->
<mapping resource="pojo/BillingDetails.hbm.xml" />
<mapping resource="pojo/User.hbm.xml" />
</session-factory>
</hibernate-configuration>

pojo/BillingDetails.java:

]package pojo;
import java.io.Serializable;
public abstract class BillingDetails implements Serializable{
private String id;
private String owner;
private User user;

public String getId() {
return id;
}
@SuppressWarnings("unused")
private void setId(String id) {
this.id = id;
}
public String getOwner() {
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}

pojo/CreditCard.java:

]package pojo;
public class CreditCard extends BillingDetails {
private String number;
private String expMonth;
private String expYear;

public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public String getExpMonth() {
return expMonth;
}
public void setExpMonth(String expMonth) {
this.expMonth = expMonth;
}
public String getExpYear() {
return expYear;
}
public void setExpYear(String expYear) {
this.expYear = expYear;
}
}

pojo/BankAccount.java:

]package pojo;
public class BankAccount extends BillingDetails {
private String account;
private String bankname;
private String swift;

public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getBankname() {
return bankname;
}
public void setBankname(String bankname) {
this.bankname = bankname;
}
public String getSwift() {
return swift;
}
public void setSwift(String swift) {
this.swift = swift;
}
}

pojo/BillingDetails.hbm.xml:

]<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pojo">
<class name="BillingDetails" abstract="true" dynamic-insert="true" dynamic-update="true">
<id name="id" column="ID" type="string">
<generator class="uuid.hex" />
</id>
<property name="owner" column="OWNER" type="string"/>
<one-to-one name="user" class="User" property-ref="billingDetails"/>
<union-subclass name="BankAccount" table="A_BANKACCOUNT">
<property name="account" column="ACCOUNT" type="string"/>
<property name="bankname" column="BANKNAME" type="string"/>
<property name="swift" column="SWIFT" type="string"/>
</union-subclass>
<union-subclass name="CreditCard" table="A_CREDITCARD">
<property name="number" column="NUM" type="string"/>
<property name="expMonth" column="EXPMONTH" type="string"/>
<property name="expYear" column="EXPYEAR" type="string"/>
</union-subclass>
</class>
</hibernate-mapping>

pojo/User.java:

]package pojo;
import java.io.Serializable;
public class User implements Serializable {
private String id;
private String name;
private int age;
private String password;
private BillingDetails billingDetails;

public String getId() {
return id;
}
@SuppressWarnings("unused")
private void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public BillingDetails getBillingDetails() {
return billingDetails;
}
public void setBillingDetails(BillingDetails billingDetails) {
this.billingDetails = billingDetails;
}
}

pojo/User.hbm.xml:

]<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="pojo">
<class name="User" table="A_USER" dynamic-insert="true" dynamic-update="true">
<id name="id" column="ID" type="string">
<generator class="uuid.hex" />
</id>
<property name="name" column="NAME" type="string"/>
<property name="age" column="AGE" type="integer"/>
<property name="password" column="PASSWORD" type="string"/>
<!-- 这里加上unique="true"就成了一对一关联 -->
<many-to-one name="billingDetails" class="BillingDetails" column="BILLINGDETAILS_ID"
cascade="save-update"/>
</class>
</hibernate-mapping>

util/HibernateUtil.java:

]package util;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sessionFactory;
static{
try {
sessionFactory = new Configuration().configure().buildSessionFactory();
} catch (Throwable e) {
throw new ExceptionInInitializerError(e);
}
}
public static SessionFactory getSessionFactory(){
return sessionFactory;
}
public static void shutdown(){
getSessionFactory().close();
}
}

util/Manager.java:

]package util;
import org.hibernate.Session;
import org.hibernate.Transaction;
import pojo.BankAccount;
import pojo.CreditCard;
import pojo.User;
public class Manager {
@SuppressWarnings("unused")
public static void main(String[] args) {

BankAccount ba = new BankAccount();
ba.setAccount("ba111");
ba.setBankname("ba222");
ba.setOwner("ba333");
ba.setSwift("ba444");

User user = new User();
user.setAge(30);
user.setName("fhd");
user.setPassword("999999");
user.setBillingDetails(ba);

CreditCard cc = new CreditCard();
cc.setExpMonth("5");
cc.setExpYear("2010");
cc.setOwner("ba555");
cc.setNumber("55");

User user1 = new User();
user1.setAge(30);
user1.setName("fhd555");
user1.setPassword("555555");
user1.setBillingDetails(cc);

Session session = HibernateUtil.getSessionFactory().openSession();
Transaction transaction = session.beginTransaction();

session.save(user);
session.save(user1);

User user3 = (User) session.get(User.class, "402881832b4e5bb4012b4e5bb5050001");

/**
* 因为默认使用了lazy="true",所以hibernate使用了代理.user3.getBillingDetails()时，返回的是代理类。
* 为了执行代理安全的类型转换，可以使用load()
* BankAccount ba = session.load(BankAccount.class,user3.getBillingDetails().getId());
*/
try {
BankAccount ba3 = (BankAccount)user3.getBillingDetails();
} catch (ClassCastException e) {
System.out.println("类型转换错误");
}

//导航测试
CreditCard cc4 = (CreditCard) session.get(CreditCard.class, "402881832b4e5bb4012b4e5bb50f0004");
System.out.println("userName:" + cc4.getUser().getName());

transaction.commit();
session.close();
}
}

表结构：

]A_BANKACCOUNT表：
ID,
OWNER,
ACCOUNT,
BANKNAME,
SWIFT
A_CREDITCARD表：
ID,
OWNER,
NUM,
EXPMONTH,
EXPYEAR
A_USER表：
ID,
NAME,
AGE,
PASSWORD,
BILLINGDETAILS_ID