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