hibernate--ID生成策略--annotation

annotation: @GeneratedValue

a) 自定义ID

b)auto: 对mysql默认使用auto_increment, 对oracle使用hibernate_sequence

c)identity 如何使用?  @GeneratedValue(strategy=GenerationType.IDENTITY)  oracle不可用, mysql,sql server可以用

d)sequence: 如何使用?  @GeneratedValue(strategy=GenerationType.SEQUENCE)   只能oracle使用, 需要调整hibernate.cfg.hml里配置

e) table: @TableGenerator

1. 新建java项目,  引入hibernate, junit(user library)和sql包

2. 新建包 com.bjsxt.hibernate, class: Teacher.java:

注意这两项

@Id

@GeneratedValue

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.Table;

@Entity

@Table(name="_Teacher")

public class Teacher {

	private int id;

	private String name;

	private String title;

	@Id

	@GeneratedValue

	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 String getTitle() {

		return title;

	}

	public void setTitle(String title) {

		this.title = title;

	}

}

　　

3. 配置hibernate.cfg.xml放在src下.    update重要, 否则不用新生成id

<?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>

        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>

        <property name="connection.url">jdbc:mysql://localhost/hibernate</property>

        <property name="connection.username">root</property>

        <property name="connection.password">linda0213</property>

        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

       <!--

        <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>

        <property name="connection.url">jdbc:oracle:thin:@localhost:1521:SXT</property>

        <property name="connection.username">scott</property>

        <property name="connection.password">tiger</property>

      	<property name="dialect">org.hibernate.dialect.OracleDialect</property>

       -->

        <!-- JDBC connection pool (use the built-in) -->

		<!--<property name="connection.pool_size">1</property> -->

        <!-- SQL dialect -->

		<property name="dialect">org.hibernate.dialect.MySQLDialect</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>

		<property name="format_sql">true</property>

        <!-- Drop and re-create the database schema on startup-->

        <!--<property name="hbm2ddl.auto">create</property> -->

        <property name="hbm2ddl.auto">update</property>

		<!--<mapping class="com.bjsxt.hibernate.model.Student"/> -->

		<!--<mapping resource ="com/bjsxt/hibernate/model/Student.hbm.xml"/> -->

  		<mapping class="com.bjsxt.hibernate.Teacher"/>

    </session-factory>

</hibernate-configuration>

4. 创建log4j.properties在src下:　

### direct log messages to stdout ###

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.Target=System.out

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### direct messages to file hibernate.log ###

#log4j.appender.file=org.apache.log4j.FileAppender

#log4j.appender.file.File=hibernate.log

#log4j.appender.file.layout=org.apache.log4j.PatternLayout

#log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

### set log levels - for more verbose logging change 'info' to 'debug' ###

log4j.rootLogger=warn, stdout

#log4j.logger.org.hibernate=info

#log4j.logger.org.hibernate=debug

### log HQL query parser activity

#log4j.logger.org.hibernate.hql.ast.AST=debug

### log just the SQL

#log4j.logger.org.hibernate.SQL=debug

### log JDBC bind parameters ###

#log4j.logger.org.hibernate.type=info

#log4j.logger.org.hibernate.type=debug

### log schema export/update ###

log4j.logger.org.hibernate.tool.hbm2ddl=debug

### log HQL parse trees

#log4j.logger.org.hibernate.hql=debug

### log cache activity ###

#log4j.logger.org.hibernate.cache=debug

### log transaction activity

#log4j.logger.org.hibernate.transaction=debug

### log JDBC resource acquisition

#log4j.logger.org.hibernate.jdbc=debug

### enable the following line if you want to track down connection ###

### leakages when using DriverManagerConnectionProvider ###

#log4j.logger.org.hibernate.connection.DriverManagerConnectionProvider=trace

5. 项目右键新建source folder---"test"

6. 项目下新建package和model里的package同名;

7. 新建junit test文件:

package com.bjsxt.hibernate;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.AnnotationConfiguration;

import org.junit.AfterClass;

import org.junit.BeforeClass;

import org.junit.Test;

public class HibernateIDTest {

	private static SessionFactory sf=null;

	@BeforeClass

	public static void beforeClass(){

		sf=new AnnotationConfiguration().configure().buildSessionFactory();

	}

	@Test

	public void testTeacherSave() {

		Teacher t =new Teacher();

		t.setName("wdf");

		t.setTitle("higfdfsdfsadh");

		Session session =  sf.openSession();

		session.beginTransaction();

		session.save(t);

		session.getTransaction().commit();

		session.close();

	}

	@AfterClass

	public static void afterClass(){

		sf.close();

	}

}

　　

8. run as->junit test, 就会自动递增id, 生成新纪录