hibernate之主键生成策略
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hibernate的主键生成器:
generator元素:表示了一个主键生成器,它用来为持久化类实例生成唯一的标识 。
我们先写实体类:
Student.java
package com.huang.two.entity; public class Student private Integer sid; private String sname; public Integer getSid() return sid; public void setSid(Integer sid) this.sid = sid; public String getSname() return sname; public void setSname(String sname) this.sname = sname; @Override public String toString() return "Student [sid=" + sid + ", sname=" + sname + "]"; public Student(Integer sid, String sname) super(); this.sid = sid; this.sname = sname; public Student() super();
Worker.java
package com.huang.two.entity; public class Worker private String wid; private String wname; public String getWid() return wid; public void setWid(String wid) this.wid = wid; public String getWname() return wname; public void setWname(String wname) this.wname = wname; @Override public String toString() return "Worker [wid=" + wid + ", wname=" + wname + "]"; public Worker(String wid, String wname) super(); this.wid = wid; this.wname = wname; public Worker() super();
工具类:
Sessionfactory.java
package com.huang.two.util; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; /** * 仅在学习hibernate的工程中使用,进入spring的学习后会有ssh来代替它 * 作用: * 用来检测hibernate中的配置文件的准确性 * hibernate.cfg.xml * *.hbm.xml * @author Admin * */ public class SessionFactoryUtils private static SessionFactory sessionFactory; static Configuration cfg = new Configuration().configure("hibernate.cfg.xml"); sessionFactory = cfg.buildSessionFactory(); public static Session openSession() // 从本地的线程中获取session会话,第一次肯定是获取不到的,那么需要重新让sessionfactory创建一个session出来 // 第二次就能够对第一次创建的session反复利用,节约性能 Session session = sessionFactory.getCurrentSession(); if(session == null) session = sessionFactory.openSession(); return session; public static void closeSession() Session session = sessionFactory.getCurrentSession(); if(session != null && session.isOpen()) session.close(); public static void main(String[] args) Session session = SessionFactoryUtils.openSession(); session.beginTransaction(); System.out.println(session.isConnected()); SessionFactoryUtils.closeSession(); System.out.println(session.isConnected());
程序员自己控制:assigned
Student.hbm.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.huang.two.entity.Student" table="t_hibernate_student"> <id name="sid" type="java.lang.Integer" column="sid"> <!-- <generator class="assigned" /> --> <!-- <generator class="identity" /> --> <generator class="increment" /> <!-- <generator class="sequence" /> --> <!-- <generator class="sequence" > <param name="sequence_name">aaa</param> </generator> --> <!-- <generator class="com.javaxl.two.id.Myts" /> --> </id> <property name="sname" type="java.lang.String" column="sname"> </property> </class> </hibernate-mapping>
Worker.hbm.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.huang.two.entity.Worker" table="t_hibernate_worker"> <id name="wid" type="java.lang.String" column="wid"> <!-- <generator class="assigned" /> --> <generator class="com.huang.two.id.MyTsGenerator" /> <!-- <generator class="sequence" > <param name="sequence_name">aaa</param> </generator> --> <!-- <generator class="com.javaxl.two.id.Myts" /> --> </id> <property name="wname" type="java.lang.String" column="wname"> </property> </class> </hibernate-mapping>
数据库控制: identity(标识列/自动增长) sequence
然后在hibernate.cfg.xml中添加实体映射文件(主键生成策略)
hibernate.cfg.xml
<?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> <!-- 1. 数据库相关 --> <property name="connection.username">huang</property> <property name="connection.password">root</property> <property name="connection.url">jdbc:mysql://localhost:3306/huang?useUnicode=true&characterEncoding=UTF-8 </property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- 配置本地事务(No CurrentSessionContext configured!) --> <property name="hibernate.current_session_context_class">thread</property> <!-- 2. 调试相关 --> <property name="show_sql">true</property> <property name="format_sql">true</property> <!-- 3. 添加实体映射文件 --> <mapping resource="com/huang/one/entity/User.hbm.xml" /> <!-- 主键生成策略 --> <mapping resource="com/huang/two/entity/Student.hbm.xml" /> <mapping resource="com/huang/two/entity/Worker.hbm.xml" /> </session-factory> </hibernate-configuration>
然后测试一下
DemoDao.java
hibernate中的主键生成策略
1、人工控制
2、数据库控制
3、hibernate控制
4、自定义主键生成策略
package com.huang.two.dao; import org.hibernate.Session; import org.hibernate.Transaction; import com.huang.two.entity.Student; import com.huang.two.entity.Worker; import com.huang.two.util.SessionFactoryUtils; public class DemoDao /** * 新增学生 * @param stu */ public void addStudent(Student stu) Session session = SessionFactoryUtils.openSession(); Transaction transaction = session.beginTransaction(); session.save(stu); transaction.commit(); SessionFactoryUtils.closeSession(); /** * 新增工人 * @param worker */ public void addWorker(Worker worker) Session session = SessionFactoryUtils.openSession(); Transaction transaction = session.beginTransaction(); session.save(worker); transaction.commit(); SessionFactoryUtils.closeSession();
public static void main(String[] args)
DemoDao dao=new DemoDao();
Student stu=new Student();
stu.setSname("huang");
stu.setSid(110);
dao.addStudent(stu);
DemoDao.java
package com.huang.two.dao; import org.hibernate.Session; import org.hibernate.Transaction; import com.huang.two.entity.Student; import com.huang.two.entity.Worker; import com.huang.two.util.SessionFactoryUtils; /** * hibernate中的主键生成策略 * 1、人工控制 * 2、数据库控制 * 3、hibernate控制 * 4、自定义主键生成策略 * @author Admin * */ public class DemoDao /** * 新增学生 * @param stu */ public void addStudent(Student stu) Session session = SessionFactoryUtils.openSession(); Transaction transaction = session.beginTransaction(); session.save(stu); transaction.commit(); SessionFactoryUtils.closeSession(); /** * 新增工人 * @param worker */ public void addWorker(Worker worker) Session session = SessionFactoryUtils.openSession(); Transaction transaction = session.beginTransaction(); session.save(worker); transaction.commit(); SessionFactoryUtils.closeSession(); public static void testStudent() DemoDao dao=new DemoDao(); Student stu=new Student(); stu.setSname("huang"); stu.setSid(110); dao.addStudent(stu); public static void main(String[] args) DemoDao dao=new DemoDao(); Worker worker=new Worker(); worker.setWname("旺财狗"); dao.addWorker(worker);
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