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Hibernate最基础的示范

2012-09-06 
Hibernate最基础的示例有关Spring的知识大部分都已经温习完毕,今天开始转向Hibernate的温习工作了必须包hi

Hibernate最基础的示例

有关Spring的知识大部分都已经温习完毕,今天开始转向Hibernate的温习工作了必须包hibernate-distribution-3.5.3-Final\hibernate3.jar         hibernate-distribution-3.5.3-Final\lib\required\slf4j-api-1.5.8.jar         hibernate-distribution-3.5.3-Final\lib\required\slf4j-api-1.5.8.jar         hibernate-distribution-3.5.3-Final\lib\required\slf4j-api-1.5.8.jar         hibernate-distribution-3.5.3-Final\lib\required\slf4j-api-1.5.8.jar         hibernate-distribution-3.5.3-Final\lib\required\slf4j-api-1.5.8.jar首先在hibernate资源包中找到:hibernate-distribution-3.5.3-Final\project\tutorials\web\src\main\resources\hibernate.cfg.xml,将这个配置文件复制到你的项目SRC目录下,然后根据实际情况进行适当修改,我的示例中修改后为Xml代码   1. <span style="font-size: large;"><span style="font-size: large;"><?xml version="1.0" encoding="utf-8" ?>     2. <!DOCTYPE hibernate-configuration PUBLIC     3.     "-//Hibernate/Hibernate Configuration DTD 3.0//EN"     4.     "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">     5. <hibernate-configuration>     6.     <session-factory>     7.       <!--数据库连接设置-->     8.         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>     9.         <property name="connection.url">jdbc:mysql:///test</property>    10.         <property name="connection.username">root</property>    11.         <property name="connection.password">root</property>    12.     13.         <!--JDBC连接池大小-->    14.         <property name="connection.pool_size">2</property>    15.         <!-- 数据库语言 -->    16.         <property name="dialect">org.hibernate.dialect.MySQLDialect</property>    17.         <!-- Hibernate当前的会话上下文 -->    18.         <property name="current_session_context_class">org.hibernate.context.ManagedSessionContext</property>    19.         <!-- 禁用二级缓存 -->    20.         <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>    21.         <!-- 控制台显示SQL语句 -->    22.         <property name="show_sql">true</property>    23.        <!-- 格式化SQL语句 -->    24.         <property name="hibernate.format_sql">true</property>    25.     26.     <!--    27.         启动时删数据库中的表,然后创建,退出时不删除数据表     28.         <property name="hbm2ddl.auto">create</property>    29.     -->    30.     <!--    31.         启动时删数据库中的表,然后创建,退出时自动删除所有表     32.         <property name="hbm2ddl.auto">create-drop</property>    33.     -->    34.     <!--    35.         自动修改,如果表结构与实体类不一致,那么就更新表结构,数据会保留    36.         (如果原表不存在,就创建新表;如果缺少相应的字段,就加入;对于原来存在的多余字段,不作处理)    37.         <property name="hbm2ddl.auto">update</property>    38.     -->    39.     <!--    40.         自动校验,如果表结构与实体类不一致,那么不做任何操作,报错    41.          <property name="hbm2ddl.auto">validate</property>    42.     -->    43.          <!-- Drop and re-create the database schema on startup -->    44.         <property name="hbm2ddl.auto">create</property>    45.     46.         <!-- 实体关系映射文件 -->    47.         <mapping resource="com/javacrazyer/domain/Student.hbm.xml"/>    48.     </session-factory>    49. </hibernate-configuration></span></span>  <?xml version="1.0" encoding="utf-8" ?><!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 3.0//EN""http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory>  <!--数据库连接设置-->        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>        <property name="connection.url">jdbc:mysql:///test</property>        <property name="connection.username">root</property>        <property name="connection.password">root</property>        <!--JDBC连接池大小-->        <property name="connection.pool_size">2</property>        <!-- 数据库语言 -->        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>        <!-- Hibernate当前的会话上下文 -->        <property name="current_session_context_class">org.hibernate.context.ManagedSessionContext</property>        <!-- 禁用二级缓存 -->        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>        <!-- 控制台显示SQL语句 -->        <property name="show_sql">true</property>       <!-- 格式化SQL语句 -->    <property name="hibernate.format_sql">true</property><!--启动时删数据库中的表,然后创建,退出时不删除数据表 <property name="hbm2ddl.auto">create</property>--><!--启动时删数据库中的表,然后创建,退出时自动删除所有表 <property name="hbm2ddl.auto">create-drop</property>--><!--自动修改,如果表结构与实体类不一致,那么就更新表结构,数据会保留(如果原表不存在,就创建新表;如果缺少相应的字段,就加入;对于原来存在的多余字段,不作处理)<property name="hbm2ddl.auto">update</property>--><!--自动校验,如果表结构与实体类不一致,那么不做任何操作,报错 <property name="hbm2ddl.auto">validate</property>-->         <!-- Drop and re-create the database schema on startup -->        <property name="hbm2ddl.auto">create</property>        <!-- 实体关系映射文件 -->        <mapping resource="com/javacrazyer/domain/Student.hbm.xml"/></session-factory></hibernate-configuration> 数据库方言一定要设定对,跟数据库驱动匹配org.hibernate.dialect.MySQLDialect 否则的话就会出现下面这个错误Java代码   1. <span style="font-size: large;"><span style="font-size: large;">Unknown table 'system_sequences' in information_schema</span></span>  Unknown table 'system_sequences' in information_schema 其次,看看实体类Student.javaJava代码   1. <span style="font-size: large;"><span style="font-size: large;">package com.javacrazyer.domain;     2.      3. import java.util.Date;     4.      5. /**    6.  * 学生实体类 --> 按JavaBean的形式定义    7.  *     8.  */     9. public class Student {    10.     private int id;  //OID 对象标识符    11.     private String name;    12.     private int age;    13.     private boolean gender;    14.     private Date birthday;    15.     private double score;    16.         17.     public int getId() {    18.         return id;    19.     }    20.     public void setId(int id) {    21.         this.id = id;    22.     }    23.     public String getName() {    24.         return name;    25.     }    26.     public void setName(String name) {    27.         this.name = name;    28.     }    29.     public int getAge() {    30.         return age;    31.     }    32.     public void setAge(int age) {    33.         this.age = age;    34.     }    35.     public boolean isGender() {    36.         return gender;    37.     }    38.     public void setGender(boolean gender) {    39.         this.gender = gender;    40.     }    41.     public Date getBirthday() {    42.         return birthday;    43.     }    44.     public void setBirthday(Date birthday) {    45.         this.birthday = birthday;    46.     }    47.     public double getScore() {    48.         return score;    49.     }    50.     public void setScore(double score) {    51.         this.score = score;    52.     }    53.         54.     @Override    55.     public String toString(){    56.         return "id=" + id + ",name=" + name + ",gender=" + gender + ",age=" + age    57.         + ",birthday=" + this.birthday + ",score=" + score;    58.     }    59.         60. }</span></span>  package com.javacrazyer.domain;import java.util.Date;/** * 学生实体类 --> 按JavaBean的形式定义 *  */public class Student {private int id;  //OID 对象标识符private String name;private int age;private boolean gender;private Date birthday;private double score;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public boolean isGender() {return gender;}public void setGender(boolean gender) {this.gender = gender;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}public double getScore() {return score;}public void setScore(double score) {this.score = score;}@Overridepublic String toString(){return "id=" + id + ",name=" + name + ",gender=" + gender + ",age=" + age+ ",birthday=" + this.birthday + ",score=" + score;}} 实体关系映射文件Student.hbm.xml,具体内容也可以参照hibernate资源包下:hibernate-distribution-3.5.3Final\project\tutorials\web\src\main\resources\org\hibernate\tutorial\domain\Person.hbm.xml那么进行修改后的内容为Xml代码   1. <span style="font-size: large;"><span style="font-size: large;"><?xml version="1.0" encoding="UTF-8"?>     2. <!DOCTYPE hibernate-mapping SYSTEM "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >     3. <hibernate-mapping>     4.     <class name="com.javacrazyer.domain.Student" table="student">     5.         <id name="id" column="id">     6.             <generator column="name"/>     9.         <property name="age"/>    10.         <property name="gender"/>    11.         <property name="birthday"/>    12.         <property name="score"/>    13.     </class>    14. </hibernate-mapping></span></span>  <?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping SYSTEM "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" ><hibernate-mapping><class name="com.javacrazyer.domain.Student" table="student"><id name="id" column="id">            <generator column="name"/>        <property name="age"/>        <property name="gender"/>        <property name="birthday"/>        <property name="score"/></class></hibernate-mapping> 现在介绍下hbm.xml映射文件中各种属性的介绍吧1.class 节点name: 类名table: 类对应表名,默认为类名称dynamic-update: 生成更新字段时,只包含发生变动的字段,默认为false。dynamic-insert: 生成insert语句时仅包含非null字段Proxy: 代理类,默认为空discriminator-value: 子类辨别标识用于多态支持where: 通过限定条件查询结果集。如:查询有籍在校学生的信息可以使用"where studentstatus='0'"2.id节点1.column                字段名称2.type                  字段类型3.length                字段长度4.unsaved-value         用于判断对象值是否已经保存5.generator-class       主键产生方式                        assigned                        hilo                        seqhilo                        increment                        identity                        sequence                        native                        uuid.hex                        uuid.string                        foreign---------------------------------------------------------------------------主键产生方式说明increment(递增) 用于为long, short或者int类型生成唯一标识。只有在没有其他进程往同一张表中插入数据时才能使用。 在集群下不要使用。identity 对DB2,MySQL, MS SQL Server, Sybase和HypersonicSQL的内置标识字段提供支持。返回的标识符是long, short 或者int类型的。sequence (序列) 在DB2,PostgreSQL, Oracle, SAP DB, McKoi中使用序列(sequence),而在Interbase中使用生成器(generator)。返回的标识符是long, short或者 int类型的。hilo (高低位) 使用一个高/低位算法来高效的生成long, short或者 int类型的标识符。给定一个表和字段(默认分别是是hibernate_unique_key 和next_hi)作为高位值得来源。高/低位算法生成的标识符只在一个特定的数据库中是唯一的。在使用JTA获得的连接或者用户自行提供的连接中,不要 使用这种生成器。seqhilo(使用序列的高低位) 使用一个高/低位算法来高效的生成long, short或者 int类型的标识符,给定一个数据库序列(sequence)的名字。uuid.hex 用一个128-bit的UUID算法生成字符串类型的标识符。在一个网络中唯一(使用了IP地址)。UUID被编码为一个32位16进制数字的字符串。uuid.string 使用同样的UUID算法。UUID被编码为一个16个字符长的任意ASCII字符组成的字符串。不能使用在PostgreSQL数据库中native(本地) 根据底层数据库的能力选择identity, sequence 或者hilo中的一个。assigned(程序设置) 让应用程序在save()之前为对象分配一个标示符。foreign(外部引用)-------------------------------------------------3.property 节点1.column                数据库表字段名称2.type                  类型3.length                长度4.not-null              字段是否允许为空5.unique                字段是否允许唯一(是否允许重复值)6.insert                insert操作时,是否允许包含本字段数值7.update                update操作时,是否包含本字段数据特别说明现在有个问题,按平常思路就是,得在数据库中创建一个student表吧,字段及类型得与Student类吻合,其实不用,为什么这么说,因为在 hibernate.cfg.xml中 <property name="hibernate.hbm2ddl.auto">update</property>这句话配置的值为update就表示没有表的情况下会在执行数据库操作前自动创建数据库表,这下就省了好多事了不过,如果你非要手工去创建,写SQL语句在数据库工具中也没必要,hibernate有相应的API支持你生成对应的数据库表下面这个类就就可以创建数据库表的类DBScriptExport .JavaJava代码   1. <span style="font-size: large;"><span style="font-size: large;">package com.javacrazyer.common;     2.      3. import org.hibernate.cfg.Configuration;     4. import org.hibernate.tool.hbm2ddl.SchemaExport;     5.      6. /**    7.  * 根据对象关系映射文件直接生成数据库表或生成建表的脚本    8.  *     9.  */    10. public class DBScriptExport {    11.     12.     public static void main(String[] args) {    13.         export2File("dbcript.sql");    14.     }    15.         16.     public static void export2DB(){    17.         //加载Hibernate的全局配置文件    18.         Configuration config = new Configuration().configure();    19.         SchemaExport export = new SchemaExport(config);    20.         export.create(true, true);    21.     }    22.         23.     public static void export2File(String dest){    24.         Configuration config = new Configuration().configure();    25.         SchemaExport export = new SchemaExport(config);    26.             27.         export.setOutputFile(dest)    28.             .setDelimiter(";")    29.             .setFormat(true)    30.             .create(true, false);    31.     }    32.     33. }    34. </span></span>  package com.javacrazyer.common;import org.hibernate.cfg.Configuration;import org.hibernate.tool.hbm2ddl.SchemaExport;/** * 根据对象关系映射文件直接生成数据库表或生成建表的脚本 *  */public class DBScriptExport {public static void main(String[] args) {export2File("dbcript.sql");}public static void export2DB(){//加载Hibernate的全局配置文件Configuration config = new Configuration().configure();SchemaExport export = new SchemaExport(config);export.create(true, true);}public static void export2File(String dest){Configuration config = new Configuration().configure();SchemaExport export = new SchemaExport(config);export.setOutputFile(dest).setDelimiter(";").setFormat(true).create(true, false);}} 获取session的HibernateUtil.javaJava代码   1. <span style="font-size: large;"><span style="font-size: large;">package com.javacrazyer.common;     2.      3. import org.hibernate.Session;     4. import org.hibernate.SessionFactory;     5. import org.hibernate.cfg.Configuration;     6.      7. /**    8.  * Hibernate工具类    9.  *    10.  */    11. public class HibernateUtil {    12.     private static final SessionFactory factory;    13.         14.     private HibernateUtil(){}    15.         16.     static{    17.         //加载Hibernate全局配置文件,根据配置信息创建SessionFactory工厂实例    18.         factory = new Configuration().configure().buildSessionFactory();    19.     }    20.         21.     public static SessionFactory getSessionFactory(){    22.         return factory;    23.     }    24.         25.     public static Session getSession(){    26.         return factory.openSession();    27.     }    28. }    29. </span></span>  package com.javacrazyer.common;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;/** * Hibernate工具类 *  */public class HibernateUtil {private static final SessionFactory factory;private HibernateUtil(){}static{//加载Hibernate全局配置文件,根据配置信息创建SessionFactory工厂实例factory = new Configuration().configure().buildSessionFactory();}public static SessionFactory getSessionFactory(){return factory;}public static Session getSession(){return factory.openSession();}} 最后的测试类HibernateTest.javaJava代码   1. <span style="font-size: large;"><span style="font-size: large;">package com.javacrazyer.test;     2.      3. import java.util.Date;     4. import java.util.List;     5.      6. import org.hibernate.Criteria;     7. import org.hibernate.HibernateException;     8. import org.hibernate.Query;     9. import org.hibernate.Session;    10. import org.hibernate.Transaction;    11. import org.hibernate.criterion.Order;    12. import org.junit.Assert;    13. import org.junit.Test;    14.     15. import com.javacrazyer.common.HibernateUtil;    16. import com.javacrazyer.domain.Student;    17.     18. /**   19.  * 使用Hibernate API完成CRUD   20.  * 更复杂的持久化操作需要使用到Query接口   21.  *    22.  */    23. public class HibernateTest {    24.         25.     @Test    26.     public void testAdd(){    27.         Student stu = new Student();    28.         stu.setName("test");    29.         stu.setBirthday(new Date());    30.         stu.setAge(1);    31.         stu.setGender(true);    32.         stu.setScore(66.8);    33.             34.         //利用工厂打开一个Session实例    35.         Session session = HibernateUtil.getSession();    36.             37.         //开启一个操作事务    38.         Transaction tx = session.beginTransaction();    39.             40.         //利用session进行持久化操作    41.         session.save(stu);    42.             43.         //提交事务    44.         tx.commit();    45.             46.         //关闭Session    47.         session.close();    48.     }    49.         50.     @Test    51.     public void getStu(){    52.             53.         //持久化管理器    54.         Session session = null;    55.         Transaction tx = null;    56.         try{    57.             session = HibernateUtil.getSession();    58.             59.             tx = session.beginTransaction();    60.             61.             //根据ID查询实体对象    62.             Student stu = (Student)session.get(Student.class, 1);    63.                 64.             Assert.assertNotNull(stu);    65.             System.out.println(stu);    66.             67.             tx.commit();    68.         }catch(HibernateException he){    69.             he.printStackTrace();    70.             tx.rollback();    71.         }finally{    72.             if(null != session && session.isOpen()){    73.                 try{    74.                     session.close();    75.                 }catch(HibernateException e){    76.                     e.printStackTrace();    77.                 }    78.             }    79.         }    80.     }    81.         82.     @Test    83.     public void testUpdate(){    84.         Session session = null;    85.             86.         try{    87.             session = HibernateUtil.getSession();    88.                 89.             session.beginTransaction();    90.                 91.             Student stu = (Student)session.get(Student.class, 1);    92.             stu.setName("zs");    93.             stu.setScore(52.1);    94.             95.             session.update(stu);    96.                 97.             session.getTransaction().commit();    98.         }catch(HibernateException e){    99.             Assert.fail();   100.             e.printStackTrace();   101.             session.getTransaction().rollback();   102.         }finally{   103.             if(session != null && session.isOpen()){   104.                 session.close();   105.             }   106.         }   107.     }   108.        109.     @Test   110.     public void testDelete(){   111.         Session session = null;   112.            113.         try{   114.             session = HibernateUtil.getSession();   115.             //session.beginTransaction();   116.                117.             Student stu = (Student)session.get(Student.class, 2);   118.             System.out.println(stu);   119.             session.delete(stu);   120.                121.             //session.getTransaction().commit();   122.         }catch(HibernateException e){   123.             Assert.fail();   124.             e.printStackTrace();   125.             //session.getTransaction().rollback();   126.         }finally{   127.             if(session != null && session.isOpen()){   128.                 session.close();   129.             }   130.         }   131.     }   132.        133.     @Test   134.     public void testGet(){   135.         Session session = null;   136.            137.         try{   138.             session = HibernateUtil.getSession();   139.             session.beginTransaction();   140.                141.             Student stu = (Student)session.get(Student.class, 2);   142.    143.             System.out.println(stu);   144.                145.             Student stu2 = (Student) session.get(Student.class, 2);   146.                147.             System.out.println(stu2);   148.                149.             session.getTransaction().commit();   150.         }catch(HibernateException e){   151.             Assert.fail();   152.             e.printStackTrace();   153.             session.getTransaction().rollback();   154.         }finally{   155.             if(session != null && session.isOpen()){   156.                 session.close();   157.             }   158.         }   159.     }   160.        161.     @Test   162.     public void testGet2(){   163.             Session session = null;   164.            165.             session = HibernateUtil.getSession();   166.             session.beginTransaction();   167.             Student stu = (Student)session.get(Student.class, 2);   168.             System.out.println(stu);   169.             session.getTransaction().commit();   170.             session.close();   171.                172.             session = HibernateUtil.getSession();   173.             session.beginTransaction();   174.             Student stu2 = (Student) session.get(Student.class, 2);   175.             System.out.println(stu2);   176.             session.getTransaction().commit();   177.             session.close();   178.     }   179.        180.     @SuppressWarnings("unchecked")   181.     @Test   182.     public void testQuery(){   183.         Session session = null;   184.         try{   185.             session = HibernateUtil.getSession();   186.             session.beginTransaction();   187.                188.             Query query = session.createQuery("from Student");   189.             List<Student> stus = query.list();   190.                191.             for(Student stu : stus){   192.                 System.out.println(stu);   193.             }   194.                195.             session.getTransaction().commit();   196.            197.         }catch(HibernateException e){   198.             e.printStackTrace();   199.             session.getTransaction().rollback();   200.         }finally{   201.             if(session != null && session.isOpen()){   202.                 session.close();   203.             }   204.         }   205.     }   206.        207.     @SuppressWarnings("unchecked")   208.     @Test   209.     public void testCriteria(){   210.         Session session = null;   211.         try{   212.             session = HibernateUtil.getSession();   213.             session.beginTransaction();   214.                215.             Criteria criteria = session.createCriteria(Student.class);   216.                217.             List<Student> stus = criteria.addOrder(Order.desc("id")).list();   218.                219.             for(Student stu : stus){   220.                 System.out.println(stu);   221.             }   222.                223.             session.getTransaction().commit();   224.            225.         }catch(HibernateException e){   226.             e.printStackTrace();   227.             session.getTransaction().rollback();   228.         }finally{   229.             if(session != null && session.isOpen()){   230.                 session.close();   231.             }   232.         }   233.     }   234.        235. }</span></span>  package com.javacrazyer.test;import java.util.Date;import java.util.List;import org.hibernate.Criteria;import org.hibernate.HibernateException;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.Transaction;import org.hibernate.criterion.Order;import org.junit.Assert;import org.junit.Test;import com.javacrazyer.common.HibernateUtil;import com.javacrazyer.domain.Student;/** * 使用Hibernate API完成CRUD * 更复杂的持久化操作需要使用到Query接口 *  */public class HibernateTest {@Testpublic void testAdd(){Student stu = new Student();stu.setName("test");stu.setBirthday(new Date());stu.setAge(1);stu.setGender(true);stu.setScore(66.8);//利用工厂打开一个Session实例Session session = HibernateUtil.getSession();//开启一个操作事务Transaction tx = session.beginTransaction();//利用session进行持久化操作session.save(stu);//提交事务tx.commit();//关闭Sessionsession.close();}@Testpublic void getStu(){//持久化管理器Session session = null;Transaction tx = null;try{session = HibernateUtil.getSession();tx = session.beginTransaction();//根据ID查询实体对象Student stu = (Student)session.get(Student.class, 1);Assert.assertNotNull(stu);System.out.println(stu);tx.commit();}catch(HibernateException he){he.printStackTrace();tx.rollback();}finally{if(null != session && session.isOpen()){try{session.close();}catch(HibernateException e){e.printStackTrace();}}}}@Testpublic void testUpdate(){Session session = null;try{session = HibernateUtil.getSession();session.beginTransaction();Student stu = (Student)session.get(Student.class, 1);stu.setName("zs");stu.setScore(52.1);session.update(stu);session.getTransaction().commit();}catch(HibernateException e){Assert.fail();e.printStackTrace();session.getTransaction().rollback();}finally{if(session != null && session.isOpen()){session.close();}}}@Testpublic void testDelete(){Session session = null;try{session = HibernateUtil.getSession();//session.beginTransaction();Student stu = (Student)session.get(Student.class, 2);System.out.println(stu);session.delete(stu);//session.getTransaction().commit();}catch(HibernateException e){Assert.fail();e.printStackTrace();//session.getTransaction().rollback();}finally{if(session != null && session.isOpen()){session.close();}}}@Testpublic void testGet(){Session session = null;try{session = HibernateUtil.getSession();session.beginTransaction();Student stu = (Student)session.get(Student.class, 2);System.out.println(stu);Student stu2 = (Student) session.get(Student.class, 2);System.out.println(stu2);session.getTransaction().commit();}catch(HibernateException e){Assert.fail();e.printStackTrace();session.getTransaction().rollback();}finally{if(session != null && session.isOpen()){session.close();}}}@Testpublic void testGet2(){Session session = null;session = HibernateUtil.getSession();session.beginTransaction();Student stu = (Student)session.get(Student.class, 2);System.out.println(stu);session.getTransaction().commit();session.close();session = HibernateUtil.getSession();session.beginTransaction();Student stu2 = (Student) session.get(Student.class, 2);System.out.println(stu2);session.getTransaction().commit();session.close();}@SuppressWarnings("unchecked")@Testpublic void testQuery(){Session session = null;try{session = HibernateUtil.getSession();session.beginTransaction();Query query = session.createQuery("from Student");List<Student> stus = query.list();for(Student stu : stus){System.out.println(stu);}session.getTransaction().commit();}catch(HibernateException e){e.printStackTrace();session.getTransaction().rollback();}finally{if(session != null && session.isOpen()){session.close();}}}@SuppressWarnings("unchecked")@Testpublic void testCriteria(){Session session = null;try{session = HibernateUtil.getSession();session.beginTransaction();Criteria criteria = session.createCriteria(Student.class);List<Student> stus = criteria.addOrder(Order.desc("id")).list();for(Student stu : stus){System.out.println(stu);}session.getTransaction().commit();}catch(HibernateException e){e.printStackTrace();session.getTransaction().rollback();}finally{if(session != null && session.isOpen()){session.close();}}}} 补充说明:如果在hibernate.cfg.xml中配置的是 <property name="hibernate.hbm2ddl.auto">create</property>这种配置前提是表已经存在在这种情况下,只要你在项目的src下新建一个文件夹命名为 import.sql,并且里面写上数据库插入语句,那么就会执行插入操作,为什么只是插入,这得跟create值的这种创建啊方式有关,它是启动 hibernate时先删除已存在的表,后新建表,新建的表本身就是空的,当然只能进行插入操作了import.sqlJava代码   1. <span style="font-size: large;">insert into student(name,age,gender,birthday,score) values('test2',10,false,now(),11.2);</span>  insert into student(name,age,gender,birthday,score) values('test2',10,false,now(),11.2); 这时,如果你在执行上面那个测试类的添加方法,就会发现,结果插入了两条数据,一条是import.sql中的,一条是测试方法中的,显然import.sql中的先执行,因为在hibernate启动时就执行了



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