hibernate整合遗留数据库之处理主键(外键引用非主键)

 

hibernate整合遗留数据库之处理主键(外键引用非主键)

 

通常，外键约束引用主键。外键约束是一个完整性规则，它保证被引用的表有一行所包含的键值与引用表和给定行中的键值相匹配。

遗留schema有时候会有不遵循简单的"外键引用主键"规则的外键约束。有时候外键引用非主键，一个简单的唯一列，一个自然的非主键。注意，被外键引用的非主键列必须用:unique="true"约束。

hibernate映射中你会遇到property-ref属性，它用来告诉hibernate”这是具名属性的一个镜像" ，property-ref还要求目标属性是唯一的，所以被外键引用的非主键列必须用：unique="true"约束。

 

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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/User.hbm.xml" /> <mapping resource="pojo/Item.hbm.xml" /> </session-factory> </hibernate-configuration>  

 

pojo/User.java:

package pojo; import java.io.Serializable; import java.util.HashSet; import java.util.Set; public class User implements Serializable { private String id; private String name; private String password; private int age; private Set<Item> itemSet = new HashSet<Item>(); 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 String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Set<Item> getItemSet() { return itemSet; } public void setItemSet(Set<Item> itemSet) { this.itemSet = itemSet; } //添加 public void addItem(Item item){ this.itemSet.add(item); item.setUser(this); } }  

 

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> <!-- 注意这里加了unique="true",将在被外键引用的非主键列 --> <property name="name" column="NAME" type="string" unique="true"/> <property name="password" column="PASSWORD" type="string"/> <property name="age" type="integer" column="AGE"/> <set name="itemSet" inverse="true" cascade="save-update"> <!-- 注意这里使用了property-ref="name" --> <key column="NAME" property-ref="name" not-null="true"/> <one-to-many class="Item"/> </set> </class> </hibernate-mapping>  

 

pojo/Item.java:

package pojo; import java.io.Serializable; public class Item implements Serializable { private String id; private String name; private String desc; private int price; private User user; 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 String getDesc() { return desc; } public void setDesc(String desc) { this.desc = desc; } public int getPrice() { return price; } public void setPrice(int price) { this.price = price; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } }  

 

pojo/Item.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="Item" table="A_ITEM" dynamic-insert="true" dynamic-update="true"> <id name="id" column="ID" type="string"> <generator class="uuid.hex"/> </id> <property name="name" column="ITEMNAME" type="string"/> <property name="desc" column="DESCRIPTION" type="string"/> <property name="price" column="PRICE" type="integer"/> <!-- 注意这里使用了property-ref="name" --> <many-to-one name="user" class="User" column="NAME" property-ref="name"/> </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.Item; import pojo.User; public class Manager { public static void main(String[] args) { User user = new User(); user.setAge(18); user.setName("fhd"); user.setPassword("kkk"); Item it1 = new Item(); it1.setDesc("aaaaaaa"); it1.setName("item1"); it1.setPrice(35); Item it2 = new Item(); it2.setDesc("bbbbbbb"); it2.setName("item2"); it2.setPrice(12); user.addItem(it1); user.addItem(it2); Session session = HibernateUtil.getSessionFactory().openSession(); Transaction transaction = session.beginTransaction(); session.save(user); transaction.commit(); session.close(); } }  

 

表结构：

A_USER表： ID, NAME, AGE, PASSWORD A_ITEM表: ID, ITEMNAME, DESCRIPTION, PRICE, NAME