注意事項：

1.單向一對多
　　?只需在“一”放進行配置
2.雙向一對多
?　　需要在關聯雙方都加以配置，而且需要在一的一方設置inverse=true

首先是實體類：

TAddress.java（多的一方）

public class TAddress implements Serializable { ????private static final long serialVersionUID = 1121137857691229229L; ????private Integer id; ????private String address; ????private String zipcode; ????private String tel; ????private String type; ????private TUser user;??? //必須有 ????............ }

TUser.java（一的一方）

public class TUser implements Serializable { ????private static final long serialVersionUID = 1224691192698621789L; ????private Integer id; ????private Integer age; ????private String name; ????@SuppressWarnings("rawtypes") ????private Set address = new HashSet();??? //多的一方放在集合中

?????????????.................... }

然后是各個實體類的配置文件

TAddress.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" > <!-- 一對多 --> <hibernate-mapping><class name="com.model.TAddress" table="t_address"dynamic-update="false" dynamic-insert="false"><id name="id" type="java.lang.Integer" column="id" unsaved-value="0"><generator class="native" /></id><property name="address" column="address" type="string" /><property name="tel" column="tel" type="string" /><property name="zipcode" column="zipcode" type="string" /><property name="type" column="type" type="string" /><!-- 必須有many-to-one 否則關聯字段（user_id）為null --><many-to-one name="user" class="com.model.TUser" cascade="none"outer-join="auto" update="true" insert="true" access="property" column="user_id"not-null="true"></many-to-one></class> </hibernate-mapping>

?TUser.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" > <!-- 一對多 外鍵關聯 --> <!-- Select from TUser where id=1 Select from TUser where id=1 to Select from TUser where id=1 or id=2 --> <!-- batch-size 批量加載機制 可以自定義每次批量加載的數量 --> <hibernate-mapping><class name="com.model.TUser" table="t_user" dynamic-update="true"><id name="id" type="java.lang.Integer" column="id" unsaved-value="0"><generator class="native" /></id><property name="name" column="name" /><property name="age" column="age" /><set name="address" table="t_address" cascade="all" order-by="zipcode asc"lazy="true" inverse="true"><key column="user_id" /><!-- 確定關聯的外鍵列 --><one-to-many class="com.model.TAddress" /></set></class> </hibernate-mapping>

其次是hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 2.0//EN""http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd"><hibernate-configuration><session-factory><!-- properties --><!-- 數據庫URL --><property name="hibernate.connection.url">jdbc:mysql://localhost/onetomany</property><!-- 數據庫JDBC驅動 --><property name="hibernate.connection.driver_class">org.gjt.mm.mysql.Driver</property><!-- 數據庫用戶名 --><property name="hibernate.connection.username">root</property><!-- 數據庫密碼 --><property name="hibernate.connection.password">hello</property><!-- 數據庫方言 --><property name="dialect">net.sf.hibernate.dialect.MySQLDialect</property><!-- 是否日志調試 --><property name="show_sql">true</property><!-- 是否使用數據庫外連接 --><property name="use_outer_join">true</property><!-- 事務管理 使用JDBC Transaction（使用JTA會報錯） --><property name="transaction.factory_class">net.sf.hibernate.transaction.JDBCTransactionFactory</property><!-- 指定hibernate每次提交的SQL數量 對批量操作的性能提升幫助很大！！！！！！！！！！！！！ --><property name="hibernate.jdbc.batch_size">25</property><!-- 映射文件配置，配置文件名必須包含其相對于根的全路徑 --><mapping resource="com/model/TUser.hbm.xml" /><mapping resource="com/model/TAddress.hbm.xml" /></session-factory></hibernate-configuration>

測試代碼（部分）

增加

public void testSave(){ ????????try { ????????????Transaction tx=session.beginTransaction(); ????????????? //????????? TUser user=(TUser) session.load(TUser.class, 1); ????????????? ????????????TUser user=new TUser(); ????????????user.setName("zhangsan"); ????????????user.setAge(20); ????????????? ????????????TAddress address=new TAddress(); ????????????address.setAddress("jingsan"); ????????????address.setTel("1361380"); ????????????address.setZipcode("45000"); ????????????address.setType("java"); ????????????address.setUser(user); //設置關聯的TUser對象 ????????????user.getAddress().add(address); ????????????? ????????????session.save(user);?? //級聯更新 ????????????tx.commit(); ????????} catch (HibernateException e) { ????????????e.printStackTrace(); ????????} ????}

查詢

public void testLoad(){ ????try { ????????Transaction tx=session.beginTransaction(); ????????String hql="from TUser where name='zhangsan'"; ????????List list=session.createQuery(hql).list(); ????????System.out.println("-------------1------------"); ????????Iterator iter=list.iterator(); ????????while(iter.hasNext()){ ????????????TUser user=(TUser) iter.next(); ????????????System.out.println("--------------2------------"); ????????????System.out.println("user.name="+user.getName()); ????????????System.out.println("--------------3------------"); ????????????System.out.println("user.address="+user.getAddress().size()); ????????????System.out.println("--------------4------------"); ????????} ????} catch (HibernateException e) { ????????e.printStackTrace(); ????} ????? }

批量插入（可以提高性能）

?實現機制：如果使用了批量加載機制，hibernate在進行數據查詢操作前，會自動在當前session中尋找是否還存在
?其他同類型待加載的數據，如果有，則將其查詢條件合并在當前的select語句中一并提交，這樣，通過
?一次數據庫操作即完成了多個讀取任務。

//批量插入操作性能優化? 通過配置<property name="hibernate.jdbc.batch_size">25</property> ????public void testBatchInsert(){ ????????long start=System.currentTimeMillis(); ????????this.importUserList(); ????????long end=System.currentTimeMillis(); ????????System.out.println("批量插入花費時間是"+(end-start)); ????} ????public void importUserList(){ ????????try { ????????????Transaction tx=session.beginTransaction(); ????????????for(int i=0;i<10000;i++){ ????????????????TUser user=new TUser(); ????????????????user.setName("user"+i); ????????????????session.save(user); ????????????????if(i%25==0){??? //以每25個數據作為一個處理單元 ????????????????????session.flush(); ????????????????????session.clear(); ????????????????} ????????????} ????????????tx.commit(); ????????} catch (HibernateException e) { ????????????e.printStackTrace(); ????????} ????}

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