1. 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 。
1.1 程序员自己控制：assigned
1.2 数据库控制: identity(标识列/自动增长) sequence
1.3 hibernate控制:increment uuid/uuid.hex
连接数据库的xml :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">root</property>
<property name="connection.password">123</property>
<property name="connection.url">jdbc:mysql://localhost:3306/sys?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/zl/entity/User.hbm.xml"/>
<!--主键生成策略 -->
<mapping resource="com/zl2/entity/Student.hbm.xml"/>
<mapping resource="com/zl2/entity/Worker.hbm.xml"/>
</session-factory>
</hibernate-configuration>
Student.java
package com.zl2.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;
}
public Student(Integer sid, String sname) {
super();
this.sid = sid;
this.sname = sname;
}
public Student() {
super();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Student [sid=" + sid + ", sname=" + sname + "]";
}
}
Worker.java
package com.zl2.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;
}
public Worker(String wid, String wname) {
super();
this.wid = wid;
this.wname = wname;
}
public Worker() {
super();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Worker [wid=" + wid + ", wname=" + wname + "]";
}
}
实体类映射文件 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.zl2.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="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.zl2.entity.Worker" table="t_hibernate_worker">
<id name="wid" type="java.lang.String" column="wid">
<!-- <generator class="assigned" /> -->
<!-- <generator class="sequence" /> -->
<!-- <generator class="uuid" /> -->
<generator class="com.zl2.id.MyTsGenerator" />
<!-- <generator class="sequence" /> -->
<!-- <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>
工具类 SessionFactoryUtils.java
package com.zl2.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，当进入spring的学习后就没用了，
* 后面会有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
* *.hbn.xml
* @author zl
*
*/
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());
}
}
做测试用dao层 DemoDao.java
package com.zl2.dao;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import com.zl2.entity.Student;
import com.zl2.entity.Worker;
import com.zl2.util.SessionFactoryUtils;
/**
* hibernate中的主键生成策略
* 1，人工控制
* 2，数据库控制
* 3，hibrenate控制
* 4，自定义主键生成策略
* @author zl
*
*/
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();
}
/**
* 新增功能
* @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(String[] args) {
DemoDao dao=new DemoDao();
Student stu=new Student();
stu.setSname("哈哈哈");
stu.setSid(71);
dao.addStudent(stu);
}
public static void main(String[] args) {
DemoDao dao=new DemoDao();
Worker worker=new Worker();
worker.setWname("zl");
dao.addWorker(worker);
}
}
MyTsGenerator.java
package com.zl2.id;
import java.io.Serializable;
import java.text.SimpleDateFormat;
import java.util.Date;
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.IdentifierGenerator;
public class MyTsGenerator implements IdentifierGenerator {
@Override
public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
SimpleDateFormat sdf=new SimpleDateFormat("yyyy-mm-dd HH:mm:ss");
return "book_order_"+sdf.format(new Date());
}
}
DemoDao.java
public static void main(String[] args) {
DemoDao dao=new DemoDao();
Worker worker=new Worker();
worker.setWname("哈哈哈");
dao.addWorker(worker);
}
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