HIbernate 继承关系实践2

最新推荐文章于 2025-07-28 23:27:29 发布

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#hibernate #integer #constructor #string #associations #class

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本文介绍使用Hibernate框架进行多表查询的方法，展示了如何通过配置不同的实体类及其映射关系来实现Gbook、Gdvd及Gitem之间的关联查询。文章提供了具体的POJO类定义、HBM配置文件以及测试代码样例。

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利用hibernate 实现多表查询

g_item 的主键id为 g_dvd和g_book的id的外键

POJO:

package nl.inherit; import java.io.Serializable; import org.apache.commons.lang.builder.ToStringBuilder; /** * @hibernate.class * table="g_book" * */ public class Gbook implements Serializable { /** identifier field */ private Integer id; /** nullable persistent field */ private String name; /** nullable persistent field */ private Integer pageCount; /** nullable persistent field */ private nl.inherit.Gitem gitem; /** full constructor */ public Gbook(Integer id, String name, Integer pageCount, nl.inherit.Gitem gitem) { this.id = id; this.name = name; this.pageCount = pageCount; this.gitem = gitem; } /** default constructor */ public Gbook() { } /** minimal constructor */ public Gbook(Integer id) { this.id = id; } /** * @hibernate.id * generator-class="assigned" * type="java.lang.Integer" * column="id" * */ public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } /** * @hibernate.property * column="name" * length="100" * */ public String getName() { return this.name; } public void setName(String name) { this.name = name; } /** * @hibernate.property * column="pageCount" * length="10" * */ public Integer getPageCount() { return this.pageCount; } public void setPageCount(Integer pageCount) { this.pageCount = pageCount; } /** * @hibernate.one-to-one * class="nl.inherit.Gitem" * outer-join="auto" * constrained="true" * */ public nl.inherit.Gitem getGitem() { return this.gitem; } public void setGitem(nl.inherit.Gitem gitem) { this.gitem = gitem; } public String toString() { return new ToStringBuilder(this) .append("id", getId()) .toString(); } }

package nl.inherit; import java.io.Serializable; import org.apache.commons.lang.builder.ToStringBuilder; /** * @hibernate.class * table="g_dvd" * */ public class Gdvd implements Serializable { /** identifier field */ private Integer id; /** nullable persistent field */ private String name; /** nullable persistent field */ private String regionCode; /** nullable persistent field */ private nl.inherit.Gitem gitem; /** full constructor */ public Gdvd(Integer id, String name, String regionCode, nl.inherit.Gitem gitem) { this.id = id; this.name = name; this.regionCode = regionCode; this.gitem = gitem; } /** default constructor */ public Gdvd() { } /** minimal constructor */ public Gdvd(Integer id) { this.id = id; } /** * @hibernate.id * generator-class="assigned" * type="java.lang.Integer" * column="id" * */ public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } /** * @hibernate.property * column="name" * length="100" * */ public String getName() { return this.name; } public void setName(String name) { this.name = name; } /** * @hibernate.property * column="regionCode" * length="100" * */ public String getRegionCode() { return this.regionCode; } public void setRegionCode(String regionCode) { this.regionCode = regionCode; } /** * @hibernate.one-to-one * class="nl.inherit.Gitem" * outer-join="auto" * constrained="true" * */ public nl.inherit.Gitem getGitem() { return this.gitem; } public void setGitem(nl.inherit.Gitem gitem) { this.gitem = gitem; } public String toString() { return new ToStringBuilder(this) .append("id", getId()) .toString(); } }

package nl.inherit; import java.io.Serializable; import org.apache.commons.lang.builder.ToStringBuilder; /** * @hibernate.class * table="g_item" * */ public class Gitem implements Serializable { /** identifier field */ private Integer id; /** nullable persistent field */ private String name; /** nullable persistent field */ private nl.inherit.Gbook gbook; /** nullable persistent field */ private nl.inherit.Gdvd gdvd; /** full constructor */ public Gitem(Integer id, String name, nl.inherit.Gbook gbook, nl.inherit.Gdvd gdvd) { this.id = id; this.name = name; this.gbook = gbook; this.gdvd = gdvd; } /** default constructor */ public Gitem() { } /** minimal constructor */ public Gitem(Integer id) { this.id = id; } /** * @hibernate.id * generator-class="assigned" * type="java.lang.Integer" * column="id" * */ public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } /** * @hibernate.property * column="name" * length="100" * */ public String getName() { return this.name; } public void setName(String name) { this.name = name; } /** * @hibernate.one-to-one * outer-join="auto" * */ public nl.inherit.Gbook getGbook() { return this.gbook; } public void setGbook(nl.inherit.Gbook gbook) { this.gbook = gbook; } /** * @hibernate.one-to-one * outer-join="auto" * */ public nl.inherit.Gdvd getGdvd() { return this.gdvd; } public void setGdvd(nl.inherit.Gdvd gdvd) { this.gdvd = gdvd; } public String toString() { return new ToStringBuilder(this) .append("id", getId()) .toString(); } }

HBM 配置文件

Gitem.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" > <hibernate-mapping>  <class name="nl.inherit.Gitem" table="g_item" > <meta attribute="class-description" inherit="false"> @hibernate.class table="g_item" </meta> <id name="id" type="java.lang.Integer" column="id" > <meta attribute="field-description"> @hibernate.id generator-class="assigned" type="java.lang.Integer" column="id" </meta> <generator class="assigned" /> </id> <property name="name" type="java.lang.String" column="name" length="100" > <meta attribute="field-description"> @hibernate.property column="name" length="100" </meta> </property>   <one-to-one name="gbook" class="nl.inherit.Gbook" outer-join="auto" > <meta attribute="field-description"> @hibernate.one-to-one outer-join="auto" </meta> </one-to-one>  <one-to-one name="gdvd" class="nl.inherit.Gdvd" outer-join="auto" > <meta attribute="field-description"> @hibernate.one-to-one outer-join="auto" </meta> </one-to-one> </class> </hibernate-mapping>

Gbook.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" > <hibernate-mapping>  <class name="nl.inherit.Gbook" table="g_book" > <meta attribute="class-description" inherit="false"> @hibernate.class table="g_book" </meta> <id name="id" type="java.lang.Integer" column="id" > <meta attribute="field-description"> @hibernate.id generator-class="assigned" type="java.lang.Integer" column="id" </meta> <generator class="assigned" /> </id> <property name="name" type="java.lang.String" column="name" length="100" > <meta attribute="field-description"> @hibernate.property column="name" length="100" </meta> </property> <property name="pageCount" type="java.lang.Integer" column="pageCount" length="10" > <meta attribute="field-description"> @hibernate.property column="pageCount" length="10" </meta> </property>   <one-to-one name="gitem" class="nl.inherit.Gitem" outer-join="auto" constrained="true" > <meta attribute="field-description"> @hibernate.one-to-one class="nl.inherit.Gitem" outer-join="auto" constrained="true" </meta> </one-to-one> </class> </hibernate-mapping>

Gdvd.hbm.xml

<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 2.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" > <hibernate-mapping>  <class name="nl.inherit.Gdvd" table="g_dvd" > <meta attribute="class-description" inherit="false"> @hibernate.class table="g_dvd" </meta> <meta attribute="implements" inherit="false">Item</meta> <id name="id" type="java.lang.Integer" column="id" > <meta attribute="field-description"> @hibernate.id generator-class="assigned" type="java.lang.Integer" column="id" </meta> <generator class="assigned" /> </id> <property name="name" type="java.lang.String" column="name" length="100" > <meta attribute="field-description"> @hibernate.property column="name" length="100" </meta> </property> <property name="regionCode" type="java.lang.String" column="regionCode" length="100" > <meta attribute="field-description"> @hibernate.property column="regionCode" length="100" </meta> </property>   <one-to-one name="gitem" class="nl.inherit.Gitem" outer-join="auto" constrained="true" > <meta attribute="field-description"> @hibernate.one-to-one class="nl.inherit.Gitem" outer-join="auto" constrained="true" </meta> </one-to-one> </class> </hibernate-mapping>

hibernate.hbm.xml

<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd"> <hibernate-configuration> <session-factory name="foo"> <mapping resource="nl/inherit/Gdvd.hbm.xml"/> <mapping resource="nl/inherit/Gbook.hbm.xml"/> <mapping resource="nl/inherit/Gitem.hbm.xml"/> </session-factory> </hibernate-configuration>

测试代码:

package test; import java.util.Iterator; import java.util.List; import junit.framework.TestCase; import net.sf.hibernate.HibernateException; import net.sf.hibernate.Session; import net.sf.hibernate.SessionFactory; import net.sf.hibernate.cfg.Configuration; import nl.inherit.Gbook; import nl.inherit.Gdvd; public class MoreTableTest extends TestCase { protected void tearDown() throws Exception { super.tearDown(); seesion.close(); } Session seesion = null; public void init() { System.out.println("test......."); } protected void setUp() throws Exception { super.setUp(); Configuration configuration = new Configuration().configure(); SessionFactory factory = configuration.buildSessionFactory(); seesion = factory.openSession(); } public void testItemTable(){ try { //多表联接查询 List list=seesion.createQuery("from Gitem item,Gdvd dvd where item.id=dvd.id").list(); Iterator item=list.iterator(); System.out.println(list.size()); while(item.hasNext()) { Object[] it=(Object [])item.next(); System.out.println(((nl.inherit.Gitem)it[0]).getGbook().getPageCount()); if(it[1] instanceof Gbook) { System.out.println("Gbook:"+((Gbook)it[1]).getPageCount()); } if (it[1] instanceof Gdvd) { System.out.println("Gdvd:"+((Gdvd)it[1]).getRegionCode()); } } } catch (HibernateException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public void testItem(){ try { //根据主表查询,以主表的主键ID为子表的ID,子表也被查询出来 List list=seesion.createQuery("from Gitem").list(); Iterator item=list.iterator(); System.out.println(list.size()); while(item.hasNext()) { nl.inherit.Gitem it = (nl.inherit.Gitem)item.next(); //通过主表获取子表信息 System.out.println("Gbook:"+it.getGbook().getPageCount()); System.out.println("Gdvd:"+it.getGdvd().getRegionCode()); } } catch (HibernateException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }