hibernate 入门

来源：互联网发布：法属圭亚那知乎编辑：程序博客网时间：2024/05/01 22:44

环境复杂,垃圾一大堆:

TOMCAT5.5

hibernate3.2.5

mysql5.0

proxool0.9

要点一:

web.xml中只加入管理信息,不要启动tomcat就运行pool.让hiber自己去运行.

<servlet>
   <servlet-name>Admin</servlet-name>
   <servlet-class>org.logicalcobwebs.proxool.admin.servlet.AdminServlet</servlet-class>
    </servlet>

    <servlet-mapping>
   <servlet-name>Admin</servlet-name>
   <url-pattern>/Admin</url-pattern>
</servlet-mapping>

要点二:

只需要1个工厂去绑定连接池,所以这个工厂被产生到一个共用的bean中.

如果多个工厂去管理连接池,必然会导致连接池重复调用错误!!!

并为了只有一个工厂,所以工厂代码是static代码,也是为了只有一个工厂实例!!!

要点三:

一个jsp用hibernate的例子

<%@ page import="java.text.*"%>
<%@ page import="java.util.*" %>
<%@ page import="org.hibernate.*" %>
<%@ page import="org.hibernate.cfg.*" %>
<%@ page import="po.*" %>
<%@ page contentType="text/html;charset=GB2312" %>

<jsp:useBean id="db" class="po.HibernateUtil" />

<%
  try
  {
          Calendar cal = Calendar.getInstance();
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   String mDateTime=formatter.format(cal.getTime());

   user u1 = new user();
              u1.setUser_name(mDateTime);
              u1.setUser_pass("6330111");

   Session mysession = db.getSessionFactory().openSession();
          Transaction tx = mysession.beginTransaction();
              mysession.save(u1);   //hiber API to PO
              tx.commit();
              mysession.close();
   u1=null; //end

   user u2 = new user();
   Session mys2 = db.getSessionFactory().openSession();
   Transaction tx2 = mys2.beginTransaction();
   u2=(user)mys2.get(user.class,new Integer(30)); //hiber API to PO,注意ID的类型,要一致呀!!
   tx2.commit();
          mys2.close();
   out.println(u2.getUser_pass());
   u2=null; //end

  }
  catch(Exception e)
        {
            e.printStackTrace();
       }

%>
</body>
</html>

要点四:

那一个工厂的bean:

package po;

import org.hibernate.*;
import org.hibernate.cfg.*;

public class HibernateUtil
{
public static SessionFactory sessionFactory;

static
{
  try
  {
  Configuration config = new Configuration();
  config.addClass(user.class);
  sessionFactory = config.buildSessionFactory();
  }
  catch (Throwable ex)
  {
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
}

public static SessionFactory getSessionFactory()
{
return sessionFactory;
}

}