Hibernate如何提升数据库查询的性能(四)

jdbc:mysql://localhost:3306/lockdb useUnicode=true&characterEncoding=utf8&autoReconnect=true&autoReconnectForPools=true

com.mysql.jdbc.Driver

lockdb

lockdb

org.hibernate.dialect.MySQLDialect

true

thread

update

最后要实现的就是测试主程序了，在测试主程序中包含了Hibernate的初始化代码以及悲观锁的测试方法。测试主程序的实现方法如清单14.4所示。

清单14.4 测试主程序的实现

package cn.hxex.hibernate.lock;

import java.net.URL;

import java.util.List;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.hibernate.LockMode;

import org.hibernate.Query;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

public class LockMain {

private static Log log = LogFactory.getLog( LockMain.class );

// 静态Configuration和SessionFactory对象的实例（全局唯一的）

private static Configuration configuration;

private static SessionFactory sessionFactory;

static

{

// 从默认的配置文件创建SessionFactory

try

{

URL configURL = ClassLoader.getSystemResource(

"cn/hxex/hibernate/lock/hibernate.cfg.xml" );

// 创建默认的Configuration对象的实例

configuration = new Configuration();

// 读取hibernate.properties或者hibernate.cfg.xml文件

configuration.configure( configURL );

// 使用静态变量来保持SessioFactory对象的实例

sessionFactory = configuration.buildSessionFactory();

}

catch (Throwable ex)

{

// 输出异常信息

log.error("Building SessionFactory failed.", ex);

ex.printStackTrace();

throw new ExceptionInInitializerError(ex);

}

}

public static SessionFactory getSessionFactory() {

return sessionFactory;

}

public void testPessimisticLock() {

SessionFactory sf = LockMain.getSessionFactory();

Session session = sf.getCurrentSession();

session.beginTransaction();

Query query = session.createQuery("from User user");

query.setLockMode("user", LockMode.UPGRADE);

List users = query.list();

for( int i=0; i

System.out.println( users.get( i ) );

}

session.getTransaction().commit();

}

public static void main(String[] args) {

LockMain main = new LockMain();

main.testPessimisticLock();

}

}

在上面的清单中，testPessimisticLock()方法就是测试悲观锁的方法，该方法在执行查询