事务_单个数据库_多个数据库(JTATransaction)_session context和事务边界(大多用于WEB)_悲观锁与乐观锁
事务_单个数据库_多个数据库(JTATransaction)_session context和事务边界(大多用于WEB)_悲观锁与乐观锁
事务_单个数据库_多个数据库(
JTATransaction)
JDBCTransaction
单个数据库（一个SesisonFactory对应一个数据库），由JDBC实现。
Session session = null;
Transaction tx =null;
try {
session = sessionFactory.openSession();
tx = session.beginTransaction();
//process
tx.commit();
} catch(HibernateException e){
if(tx != null)tx.rollback();throw e;
}finally {
if (session != null)session.close();
}
connection.setAutoCommit(false);
connection.commit();conn.rollback();
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JTATransaction
可以简单的理解成跨数据库的事物，由应用JTA 容器实现；
使用JTATransaction需要配置hibernate.transaction.factory_class参数，
该参数缺省值是org.hibernate.transaction. JDBCTransactionFactory，
当使用JTATransaction时需要将该参数改成org.hibernate.transaction.JTATransactionFactory，
并配置jta.UserTransaction参数JNDI名(Hibernate在启动JTATransaction时要用该值到JNDI的上下文Context中去找javax.transaction.UserTransaction)。
javax.transaction.UserTransactin tx = context.lookup(“jndiName”);
try{
tx.begin();
//多个数据库的session操作;
//session1….
//session2….
tx.commit();
}catch(Exception e){
tx.rollback(); throw e;
}
session context和事务边界(大多用于WEB)
用current_session_context_class属性来定义context（用sessionFactory.getCurrentSession()来获得session）
其值为：
1.thread：ThreadLocal来管理Session实现多个操作共享一个Session，
避免反复获取Session，并控制事务边界，
此时session不能调用close当commit或rollback的时候session会自动关闭(connection.release_mode:after_transaction)。
Open session in view：在生成（渲染）页面时保持 session打开。
2.jta：由JTA事务管理器来管理事务(connection.release_mode:after_statement)。
(模拟)_ThreadLocal来管理Session实现多个操作共享一个Session(模拟)
1.HibernateUtil工具类，添加 getThreadLocalSession()，closeSession()
public static Session getThreadLocalSession(){
Session session=(Session)threadLocalSession.get();
if(session==null){
session=getSession();
threadLocalSession.set(session);
}
return session;
}
public static void closeSession(){
Session session=(Session)threadLocalSession.get();
if(session!=null){
session.close();
threadLocalSession.set(null);
}
}
2.servlet 过滤器 (实现接口Filter)
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain filterChain) throws IOException, ServletException {
Session session = null;
Transaction tx = null;
try {
session = HibernateUtil.getThreadLocalSession();
tx = session.beginTransaction();
filterChain.doFilter(request, response);
tx.commit();
} catch (Exception e) {
if (tx != null)
tx.rollback();
throw new RuntimeException(e.getMessage(), e);
} finally {
HibernateUtil.closeSession();
}
}
3.UserDAO.java
package com.dwt1220;
public class UserDao {
public void addUser(User user){
HibernateUtil.getThreadLocalSession().save(user);
}
}
悲观锁与乐观锁
1、悲观锁由数据库来实现；
2、乐观锁hibernate用version和timestamp来实现
1、为类添加version or timestamp 字段；(timestamp必须是Date类型，version随便)
2、配置文件设置。在id标签后添加 version or timestamp 字段
User.java
package com.dwt1220;
import java.util.Date;
public class User {
private int id;
private Name name;
private Date birthday;
private int version;
// private Date timestamp;
public int getVersion() {
return version;
}
public void setVersion(int version) {
this.version = version;
}
// public Date getTimestamp() {
// return timestamp;
// }
//
// public void setTimestamp(Date timestamp) {
// this.timestamp = timestamp;
// }
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Name getName() {
return name;
}
public void setName(Name name) {
this.name = name;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
}
User.hbm.xml
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.dwt1220"> <!-- <class name="User" table"user"> table 属性可选(类对应的表名),如果表名和字段名是数据库的关节字，可以加''--> <class name="User"> <id name="id"> <generator class="native"/> </id> <!-- 必须放在id后面 --> <version name="version"/> <!-- or <timestamp name="timestamp"/> 一般使用 version方式， timestamp 不够精确 --> <component name="name"> <property name="firstName" column="first_name"></property> <property name="lastName" column="last_name"></property> </component> <property name="birthday"/> </class> </hibernate-mapping>
Test.java
package com.dwt1220;
import java.util.Date;
import org.hibernate.Session;
import org.hibernate.Transaction;
public class Test {
public static void main(String[] args) {
Name name=new Name();
name.setFirstName("firstName");
name.setLastName("lastName");
User user=new User();
user.setBirthday(new Date());
user.setName(name);
add(user);
update(1);
System.out.println("end");
query(1);
}
static void update(int id) {
Session session1 = null;
Transaction tx1 = null;
Session session2 = null;
Transaction tx2 = null;
try {
session1 = HibernateUtil.getSession();
tx1 = session1.beginTransaction();
User user1=(User)session1.get(User.class,id);
session2 = HibernateUtil.getSession();
tx2 = session1.beginTransaction();
User user2=(User)session2.get(User.class, id);
user1.getName().setFirstName("new1 fistName");
user2.getName().setFirstName("new2 fistName");
tx2.commit();
tx1.commit();//此处应版本号错误，报错。
} finally {
if (session1 != null&&session2!=null) {
session1.close();
session2.close();
}
}
}
static void query(int id) {
Session session = null;
User user=null;
try {
session = HibernateUtil.getSession();
user=(User)session.get(User.class, id);
System.out.println("User.firstname:"+user.getName().getFirstName());
} finally {
if (session != null) {
session.close();
}
}
}
static void add(Object object) {
Session session = null;
Transaction tx = null;
try {
session = HibernateUtil.getSession();
tx = session.beginTransaction();
session.save(object);
tx.commit();
// 不catch,出错会自动回滚
} finally {
if (session != null) {
session.close();
}
}
}
}