Hibernate高级实体关联映射之多值的实体关联(一对多关联,使用list)

来源：互联网发布：面板数据回归分析实例编辑：程序博客网时间：2024/04/29 02:49

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">  <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>  <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>  <property name="hibernate.connection.username">system</property>  <property name="hibernate.connection.password">password</property>  <property name="hibernate.c3p0.max_size">20</property>  <property name="hibernate.c3p0.min_size">5</property>  <property name="hibernate.c3p0.timeout">120</property>  <property name="hibernate.c3p0.max_statements">100</property>  <property name="hibernate.c3p0.idle_test_period">120</property>  <property name="hibernate.c3p0.acquire_increment">2</property>  <property name="dialect">org.hibernate.dialect.OracleDialect</property>  <property name="show_sql">true</property>  <property name="hibernate.format_sql">true</property>  <mapping resource="pojo/User.hbm.xml" /> <mapping resource="pojo/Address.hbm.xml" /> </session-factory> </hibernate-configuration>

pojo/User.java:

package pojo;import java.util.ArrayList;import java.util.List;public class User {private String id;private String userName;private String password;private String email;//使用list映射private List<Address> addressList = new ArrayList<Address>();public String getId() {return id;}@SuppressWarnings("unused")private void setId(String id) {this.id = id;}public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public List<Address> getAddressList() {return addressList;}public void setAddressList(List<Address> addressList) {this.addressList = addressList;}//双向关联public void addAddress(Address address){this.addressList.add(address);address.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="MYUSER" dynamic-insert="true" dynamic-update="true"> <id name="id" column="ID" type="string"> <generator class="uuid.hex" /> </id> <property name="userName" column="USERNAME" type="string"/> <property name="password" column="PASSWORD" type="string"/> <property name="email" column="EMAIL" type="string"/>  <list name="addressList" cascade="save-update">  <key column="USER_ID" not-null="true" update="false"/> <list-index column="ADDRESS_INDEX"/> <one-to-many class="Address"/> </list> </class> </hibernate-mapping>

pojo/Address.java:

package pojo;public class Address {private String id;private String street;private String zipCode;private String city;private User user;public String getId() {return id;}@SuppressWarnings("unused")private void setId(String id) {this.id = id;}public String getStreet() {return street;}public void setStreet(String street) {this.street = street;}public String getZipCode() {return zipCode;}public void setZipCode(String zipCode) {this.zipCode = zipCode;}public String getCity() {return city;}public void setCity(String city) {this.city = city;}public User getUser() {return user;}public void setUser(User user) {this.user = user;}}

pojo/Address.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="Address" table="ADDRESS" dynamic-insert="true" dynamic-update="true"> <id name="id" column="ID" type="string"> <generator class="uuid.hex" /> </id> <property name="street" column="STREET" type="string"/> <property name="zipCode" column="ZIPCODE" type="string"/> <property name="city" column="CITY" type="string"/>  <many-to-one name="user" column="USER_ID" class="User" not-null="true" insert="false" update="false"/> </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.Address;import pojo.User;public class Manager {public static void main(String[] args) {Address address = new Address();address.setCity("guangzhou");address.setStreet("北京路");address.setZipCode("510000");User user = new User();user.setUserName("fhd");user.setPassword("000000");user.setEmail("8888@163.com");user.addAddress(address);Session session = HibernateUtil.getSessionFactory().openSession();Transaction transaction = session.beginTransaction();session.save(user);transaction.commit();session.close();}}

表结构：

MYUSER表：ID,USERNAME,PASSWORD,EMAILADDRESS表：ID,STREET,ZIPCODE,CITY,USER_ID,ADDRESS_INDEX

输出sql:

Hibernate: insert into MYUSER (USERNAME, PASSWORD, EMAIL, ID) values (?, ?, ?, ?)Hibernate: insert into ADDRESS (STREET, ZIPCODE, CITY, USER_ID, ADDRESS_INDEX, ID) values (?, ?, ?, ?, ?, ?)

注意：User.hbm.xml中<list>不可以用inverse="true"，否则hibernate会忽略反向集合的状态。这一次，集合包含了正确地更新数据库所需的信息：它的元素的位置，因此不可用inverse="true",不然ADDRESS表中的索引列ADDRESS_INDEX就没有值了。

而在另一端，Address.hbm.xml中，<many-to-one>的多对一映射没有inverse="true"属性，那么就需要添加insert="false",

update="false"这两个属性来模拟inverse="true"，缺一不可。

设置insert和update为false具有预期的效果。如前所述，这两个属性一起使用，实际上使属性变成了只读。关联的这一端因此被任何写操作忽略，如果从set或者bag转换到list(或者任何其他被索引的集合)，这是个必要条件。

还要注意，User.hbm.xml中<list>元素中的<key>子元素，设置update="false",避免不必要的更新操作。