hibernate复习三之基本实体映射

对象表映射

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实体类--数据库表间的转换

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由于Hibernate的存储都是建立在对象基础上的，所以映射好实体类对象和数据库表是非常重要的，数据库表的设计也必须按照一定的规范来（冗余字段等就不允许存在?）

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本章的目录：

1.简单对象表映射

--搭建JUnit测试环境

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附：

搭建JUnit测试环境

1.去官网下载jar包

2.解压，复制junit-4.10.jar(我用的此时是4.10版本)到bin下的jar中

3.在项目名上右键→new→Source Folder→输入名称→finish

4.注意，你对哪个包进行测试，你就在测试下建立和那个包相同的包

5.建立测试类，需要在测试的方法前面加入”@Test”

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1.简单对象表映射，（单表无关联）

先把实体类贴出来（本人英文名jake,无需吐槽包名）

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package com.jake.hibernate.domain;import java.util.Date;public class Person {private long id;private String name;private Date birthday;public long getId() {return id;}public void setId(long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}}

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然后是映射文件:建议与实体类同包，名字为 ? 实体类名.hbm.xml

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<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.jake.hibernate.domain"><class name="Person" table="PERSON"><id name="id" column="id"><generator /></id><property name="name" column="name" /><property name="birthday" type="timestamp" column="birthday" /></class></hibernate-mapping>

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?然后是配置文件(参考文档中给的)

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<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory><!-- Database connection settings --><property name="connection.driver_class">com.mysql.jdbc.Driver</property><property name="connection.url">jdbc:mysql://localhost:3306/hibernateTest</property><property name="connection.username">root</property><property name="connection.password">123456</property><!-- JDBC connection pool (use the built-in) --><property name="connection.pool_size">10</property><!-- SQL dialect --><property name="dialect">org.hibernate.dialect.MySQL5Dialect</property><!-- Enable Hibernate's automatic session context management --><property name="current_session_context_class">thread</property><!-- Disable the second-level cache  --><property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property><!-- Echo all executed SQL to stdout --><property name="show_sql">true</property><!-- Drop and re-create the database schema on startup --><property name="hbm2ddl.auto">update</property><property name="show_sql">true</property><property name="format_sql">true</property><mapping resource="com/jake/hibernate/domain/Person.hbm.xml" /><!--<mapping resource="org/hibernate/tutorial/domain/Event.hbm.xml" /><mapping resource="org/hibernate/tutorial/domain/Person.hbm.xml" />--></session-factory></hibernate-configuration>

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?接下来是JUnit Test的代码

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package com.jake.hibernate.domain;import java.util.Date;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.junit.AfterClass;import org.junit.BeforeClass;import org.junit.Test;import com.jake.hibernate.util.HibernateUtil;public class TestPerson {private static SessionFactory sf = null;@BeforeClass// 表示Junit此类被加载到内存中就执行这个方法public static void beforClass() {sf = HibernateUtil.getSessionFactory();}@Testpublic void TestPerson() {Session session = sf.getCurrentSession();session.beginTransaction();Person p = new Person();p.setName("jake");Date d = new Date();p.setBirthday(d);session.save(p);session.getTransaction().commit();// session.close();// 注意，commit后是自动关闭session的，不需要是手动close}@AfterClasspublic static void afterClass() {sf.close();}}

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测试成功。。

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有一点出乎意料的地方是，数据库生成的是datetime型的，不是timestamp。

目前未解决。。

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接下来是annotation版本的了。。

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实体类

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package com.jake.hibernate.model;import java.util.Date; import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;import javax.persistence.Temporal;import javax.persistence.TemporalType;@Entity@Table(name = "t_person")public class Person {private long id;private String name;private Date birthday;@Id@GeneratedValue(strategy = GenerationType.AUTO)public long getId() {return id;}public void setId(long id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}@Temporal(TemporalType.TIMESTAMP)@Column(updatable = false) public Date getBirthday() {return birthday;}public void setBirthday(Date birthday) {this.birthday = birthday;}}

配置文件

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<?xml version='1.0' encoding='utf-8'?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory><!-- Database connection settings --><property name="connection.driver_class">com.mysql.jdbc.Driver</property><property name="connection.url">jdbc:mysql://localhost:3306/hibernateTest</property><property name="connection.username">root</property><property name="connection.password">123456</property><!-- JDBC connection pool (use the built-in) --><property name="connection.pool_size">10</property><!-- SQL dialect --><property name="dialect">org.hibernate.dialect.MySQL5Dialect</property><!-- Enable Hibernate's automatic session context management --><property name="current_session_context_class">thread</property><!-- Disable the second-level cache  --><property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property><!-- Echo all executed SQL to stdout --><property name="show_sql">true</property><!-- Drop and re-create the database schema on startup --><property name="hbm2ddl.auto">update</property><mapping name="code"><mapping name="code">package com.jake.hibernate.util;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;public class HibernateUtil {private static final SessionFactory sessionFactory = buildSessionFactory();private static SessionFactory buildSessionFactory() {try {return new Configuration().configure().buildSessionFactory();} catch (Throwable ex) {System.err.println("Initial SessionFactory creation failed." + ex);throw new ExceptionInInitializerError(ex);}}public static SessionFactory getSessionFactory() {return sessionFactory;}}

?JUnitTest 的代码也贴了吧～～

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package com.jake.hibernate.model;import java.util.Date;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.junit.AfterClass;import org.junit.BeforeClass;import com.jake.hibernate.util.HibernateUtil;public class PersonTest {static SessionFactory sf = null;@BeforeClasspublic static void beforeClass() {sf = HibernateUtil.getSessionFactory();}@org.junit.Testpublic void PersonTest() {Session session = sf.getCurrentSession();session.beginTransaction();Person p = new Person();Date birthday = new Date();p.setBirthday(birthday);p.setName("jake");session.save(p);session.getTransaction().commit();}@AfterClasspublic static void afterClass() {sf.close();}}

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OK。测试成功。。。

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