一、Session的保存、刪除及更新save()方法：將一個(gè)對(duì)象的屬性取出放入PreparedStatement語句中，然后向數(shù)據(jù)庫中插入n語句。例：〃打開Session，開啟事務(wù)Studentsstudents=newStudents();students.setCardId(20080929);//設(shè)置學(xué)號(hào)session.save(students);System.out.println(students.getid());//提交事務(wù)，關(guān)閉Sessionupdate()方法：例：〃打開Session，開啟事務(wù)students=(Students)session.get(Students.class,"1");students.setName("123");session.update(students);〃提交事務(wù)，關(guān)閉session批量更新：在進(jìn)行批量操作時(shí)，最好的方法是調(diào)用JDBC的API進(jìn)行操作。例：將所有學(xué)生的姓名前加上一個(gè)字符串“xiao”。Connectionconn=session.connection();PreparedStatementstmt=conn.prepareStatement("updatestudentssetsname='xiao'+sname");stmt.executeUpdate();saveOrUpdate()方法：與save方法，update方法用法相同。只是處理的細(xì)節(jié)不同。delete()方法：負(fù)責(zé)刪除一個(gè)對(duì)象例：〃打開Session,開啟事務(wù)students=(Students)session.get(Students.class,"1");session.delete(students);//提交事務(wù)，關(guān)閉Session二、通過主鍵ID取得數(shù)據(jù)對(duì)象1.get()方法：用立即加載的方式發(fā)送SQL語句，并得到已經(jīng)初始化的對(duì)象?！ù蜷_Session，開啟事務(wù)Studentsstudents=(Students)session.get(Students.class,"1")//提交事務(wù)，關(guān)閉Session2.load()方法：它返回一個(gè)代理對(duì)象，直到這個(gè)對(duì)象被訪問，此代理對(duì)象才會(huì)被初始化。students=(Students)session.load(Students.class,1);System.out.println(students.getSid());三、Query接口(重點(diǎn))1.使用“？”綁定參數(shù)例：查找age大于27,名字中有a的所有記錄，打印姓名和年齡。Studentsstudents=newStudents();Queryquery=session.createQuery("fromStudentswhereage>?andsnamelike?");query.setlnteger(0,27);query.setString(1,"%a%");Listlist=query.list();for(inti=0;i<list.size();i++){students=(Students)list.get(i);System.out.print(students.getSname()+",");System.out.println(students.getAge());}2使用“:”后跟變量的方法設(shè)置參數(shù)Studentsstudents=newStudents();Queryquery=session.createQuery("fromStudentswhereage>:minAgeandsnamelike:likeName");query.setInteger(minAge,27);query.setString(likeName,"%a%");Listlist=query.list();for(inti=0;i<list.size();i++){students=(Students)list.get(i);System.out.print(students.getSname()+",");System.out.println(students.getAge());}3.使用命名查詢(namedQuery)students.hbm.xml的源碼如下：1<?xmlversion="1.0"encoding="utf-8"?>2<!DOCTYPEhibernate-mappingPUBLIC"-//Hibernate/HibernateMappingDTD3.0//EN"3"/hibernate-mapping-3.0.dtd">4<hibernate-mapping><classname="com.zzn.hibernate.Students"table="students"schema="dbo"catalog="hibernate"><idname="sid"type="java.lang.Integer"><columnname="sid"/><generatorclass="native"></generator></id><propertyname="sname"type="java.lang.String"><columnname="sname"length="10"not-null="true"/></property><propertyname="age"type="java.lang.Integer"><columnname="age"not-null="true"/></property></class><queryname="queryStudents_byAgeAndName"><![CDATA[fromStudentswhereage>25:minAgeandsnamelike:likeName]]></query>22</hibernate-mapping>23使用命名查詢的源碼如下：1packagecom.zzn.hibernate;2importjava.util.List;3importorg.hibernate.Query;4importorg.hibernate.Session;5importorg.hibernate.SessionFactory;6importorg.hibernate.Transaction;7importorg.hibernate.cfg.Configuration;89publicclassTest3{@SuppressWarnings("unchecked")publicstaticvoidmain(String[]args){Configurationconfiguration=newConfiguration().configure();SessionFactorysessionFactory=configuration.buildSessionFactory();Sessionsession=sessionFactory.openSession();Transactiontransation=session.beginTransaction();16Studentsstudents=newStudents();Queryquery=session.getNamedQuery("queryStudents_byAgeAndName");query.setInteger("minAge",25);query.setString("likeName","%a%");Listlist=query.list();for(inti=0;i<list.size();i++){students=(Students)list.get(i);System.out.println(students.getSname());System.out.println(students.getAge());System.out.print(students.getSid());}mit();session.close();}32}33四、查詢緩存：對(duì)于有很多select語句，可insert、delete、update、語句較少的情況，使用查詢緩存性能上有一定的改善作用。反之查詢比較少的情況，這方法意義就不大了。(1)在hibernate.cfg.xml中設(shè)定hibernate.cache.use_query_cache屬性1<?xmlversion='1.0'encoding='UTF-8'?>2<!DOCTYPEhibernate-configurationPUBLIC"-//Hibernate/HibernateConfigurationDTD3.0//EN""/hibernate-configuration30.dtd">5<hibernate-configuration>6<session-factory>7<propertyname="hibernate.cache.use_query_cache">true</property>8</session-factory>9</hibernate-configuration>⑵每次建立Query實(shí)例時(shí)，執(zhí)行setCacheable(true)。1Studentsstudents=newStudents();Queryquery=session.createQuery("fromStudents");query.setCacheable(true);//準(zhǔn)許把查詢放入查詢緩存Listlist=query.list();for(inti=0;i<list.size();i++){students=(Students)list.get(i);System.out.println(students.getSname());}〃一下是再次查詢并打印Queryq=session.createQuery("fromStudents");q.setCacheable(true);Listl=q.list();for(inti=0;i<l.size();i++){students=(Students)l.get(i);System.out.println(students.getSname());}(3)從結(jié)果可以看出第一次查詢是從數(shù)據(jù)庫查詢出來的，而第二次則是從緩存中將Query中的結(jié)果返回的。五、清除緩存對(duì)象：如果在數(shù)據(jù)庫中插入1000000條數(shù)據(jù)，再插入500000條時(shí)程序拋出例外OutOfMemoryException。因?yàn)镠ibernate總是把新添加的對(duì)象加入到Session級(jí)別的緩存中。所以我們必須清除緩存。(1)clear()方法：在hibernate.cfg.xml中設(shè)置1<?xmlversion='1.0'encoding='UTF-8'?>2<!DOCTYPEhibernate-configurationPUBLIC"-//Hibernate/HibernateConfigurationDTD3.0//EN""/hibernate-configuration30.dtd">5<hibernate-configuration>6<session-factory>7<propertyname="hibernate.jdbc.batch_size">20</property>8</session-factory>9</hibernate-configuration>然后在一個(gè)合適的頻率下調(diào)用flush()清理緩存發(fā)送SQL語句，調(diào)用Session的clear()方法清空Session緩存。1//打開Session,開啟事務(wù)2for(inti=0;i<1000000;i++){3Studentsstudents=newStudents();students.setCardid();session.save(students);if(i%20)(〃第20個(gè)對(duì)象保存一次，之后馬上清空Sessionsession.flush();session.clear();}11}12//提交事務(wù)，關(guān)閉session(2)evict()方法：清除緩存中的某個(gè)對(duì)象1//打開事務(wù)Session，開啟事務(wù)for(inti=0;i<1000000;i++){Studentsstudents=newStudents();students