[原创]在虚拟主机上让Jive论坛和Hibernate共享一个数据库连接池

背景：在一台虚拟主机上（TOMCAT）已经运行了jive论坛（使用自带的数据库连接池），现在想在此虚拟主机上安装Hibernate.
问题：由于jive和Hibernate都需要使用数据库连接池,如何让它们共享一个连接池。

一种解决办法：
由于jive和Hibernate都支持通过JNDI来查找一个连接池实例，因此为虚拟主机配置一个数据库连接池并把它绑定到JNDI上即可。由于虚拟主机都禁止每个用户修改server.xml文件，因此通过编辑server.xml来给虚拟主机配置数据库连接池行不通。那么我们可以编写一个启动就自动加载的Servlet,在其中配置连接池并把它绑定到JNDI上。
这里连接池我使用了TOMCAT自带的DBCP，数据库使用mysql.

先编写一个servlet负责初始化DBCP
[code:1]
package myDataSource;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.naming.*;
import org.apache.commons.dbcp.*;

public class JndiDataSourceServlet extends HttpServlet{

public void init(ServletConfig config) throws ServletException
{
String DBUrl = config.getInitParameter("DBUrl");
if(DBUrl == null) DBUrl = "jdbc:mysql://localhost/jive";

String Username = config.getInitParameter("Username");
if(Username == null) Username = "root";

String Password = config.getInitParameter("Password");
if(Password == null) Password = "root";

String DriverClassName = config.getInitParameter("DriverClassName");
if(DriverClassName == null) DriverClassName = "org.gjt.mm.mysql.Driver";

String MaxWaitStr = config.getInitParameter("MaxWait");
if(MaxWaitStr == null) MaxWaitStr = "3000";
long MaxWait = (new Long(MaxWaitStr)).longValue();

String MaxIdleStr = config.getInitParameter("MaxIdle");
if(MaxIdleStr == null) MaxIdleStr = "10";
int MaxIdle = (new Integer(MaxIdleStr)).intValue();

String MaxActiveStr = config.getInitParameter("MaxActive");
if(MaxActiveStr == null) MaxActiveStr = "100";
int MaxActive = (new Integer(MaxActiveStr)).intValue();

String JndiName = config.getInitParameter("JndiName");
if(JndiName == null) JndiName = "my_datasource";

try{
Context initCtx = (Context)new InitialContext();
BasicDataSource bds = new BasicDataSource();

bds.setUrl(DBUrl);
bds.setUsername(Username);
bds.setPassword(Password);
bds.setDriverClassName(DriverClassName);
bds.setMaxWait(MaxWait);
bds.setMaxIdle(MaxIdle);
bds.setMaxActive(MaxActive);
initCtx.rebind(JndiName,bds);

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

}//end init(ServletConfig config)

}//end JndiDataSourceServlet
[/code:1]

之后再修改虚拟主机的web.xml，类似如下
[code:1]
<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>

<display-name>Tomcat Examples</display-name>
<description>
Tomcat Example servlets and JSP pages.
</description>

<servlet>
<servlet-name>jndiSource</servlet-name>
<servlet-class>myDataSource.JndiDataSourceServlet</servlet-class>
<init-param>
<param-name>DBUrl</param-name>
<param-value>jdbc:mysql://localhost/jive</param-value>
</init-param>
<init-param>
<param-name>Username</param-name>
<param-value>root</param-value>
</init-param>
<init-param>
<param-name>Password</param-name>
<param-value>root</param-value>
</init-param>
<init-param>
<param-name>DriverClassName</param-name>
<param-value>org.gjt.mm.mysql.Driver</param-value>
</init-param>
<init-param>
<param-name>MaxWait</param-name>
<param-value>3000</param-value>
</init-param>
<init-param>
<param-name>MaxIdle</param-name>
<param-value>10</param-value>
</init-param>
<init-param>
<param-name>MaxActive</param-name>
<param-value>100</param-value>
</init-param>
<init-param>
<param-name>JndiName</param-name>
<param-value>my_datasource</param-value>
</init-param>

<load-on-startup>1</load-on-startup>
</servlet>


</web-app>
[/code:1]

之后再把Hibernate文档中的例子--Cat 附在这里：
1、先把Hibernate.hbm.xml和Cat.hbm.xml拷贝到classes目录中。
Hibernate.hbm.xml文件：
[code:1]
<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration
PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-2.0.dtd">

<hibernate-configuration>

<session-factory>

<property name="connection.datasource">my_datasource</property>
<property name="show_sql">true</property>
<property name="dialect">net.sf.hibernate.dialect.MySQLDialect</property>

<!-- Mapping files -->
<mapping resource="Cat.hbm.xml"/>

</session-factory>

</hibernate-configuration>
[/code:1]

Cat.hbm.xml文件：
[code:1]
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

<class name="mytest.Cat" table="CAT">

<!-- A 32 hex character is our surrogate key. It's automatically
generated by Hibernate with the UUID pattern. -->
<id name="id" type="string" unsaved-value="null" >
<column name="CAT_ID" sql-type="char(32)" not-null="true"/>
<generator class="uuid.hex"/>
</id>

<!-- A cat has to have a name, but it shouldn' be too long. -->
<property name="name">
<column name="NAME" sql-type="varchar(16)" not-null="true"/>
</property>

<property name="sex"/>

<property name="weight"/>

</class>

</hibernate-mapping>
[/code:1]

Cat.java
[code:1]
package mytest;

public class Cat {

private String id;
private String name;
private char sex;
private float weight;

public Cat() {
}

public String getId() {
return id;
}

public void setId(String id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public char getSex() {
return sex;
}

public void setSex(char sex) {
this.sex = sex;
}

public float getWeight() {
return weight;
}

public void setWeight(float weight) {
this.weight = weight;
}

}
[/code:1]

HibernateUtil.java
[code:1]
package mytest;

import net.sf.hibernate.*;
import net.sf.hibernate.cfg.*;

public class HibernateUtil {

private static final SessionFactory sessionFactory;

static {
try {
sessionFactory = new Configuration().configure().buildSessionFactory();
} catch (HibernateException ex) {
throw new RuntimeException("Exception building SessionFactory: " + ex.getMessage(), ex);
}
}

public static final ThreadLocal session = new ThreadLocal();

public static Session currentSession() throws HibernateException {
Session s = (Session) session.get();
// Open a new Session, if this Thread has none yet
if (s == null) {
s = sessionFactory.openSession();
session.set(s);
}
return s;
}

public static void closeSession() throws HibernateException {
Session s = (Session) session.get();
session.set(null);
if (s != null)
s.close();
}
}
[/code:1]

最后是一个测试用的test.jsp文件
[code:1]
<%@ page contentType="text/html;CHARSET=utf8"%>
<%@ page import= "net.sf.hibernate.* "%>
<%@ page import= "mytest.* "%>
<%@ page import= "java.sql.* "%>
<%@ page import= "javax.naming.* "%>
<%@ page import= "org.apache.commons.dbcp.* "%>

<%
try{

//test jiveUser table first.

Context initCtx = new InitialContext();
Object obj = (Object) initCtx.lookup("my_datasource");
javax.sql.DataSource ds = (javax.sql.DataSource)obj;

Connection conn = ds.getConnection();
Statement stmt = conn.createStatement();
String strSql = " select userID,name from jiveUser ";

ResultSet rs = stmt.executeQuery(strSql);
while(rs.next()){
out.println(rs.getString(1));
out.println(rs.getString(2));
}
}catch(Exception ex){
ex.printStackTrace();
}




//test Hibernate.

Cat princess = new Cat();
princess.setName("Luck Cat");
princess.setSex('F');
princess.setWeight(7.4f);


Session session1 = HibernateUtil.currentSession();

Transaction tx= session1.beginTransaction();
session1.save(princess);
tx.commit();

HibernateUtil.closeSession();


%>
<hr>

[/code:1]

到此为止，在虚拟主机上配置和测试Hibernate的工作基本完成了。以上代码在Tomcat上均测试通过。
另外我刚刚接触Hibernate,如果配置或代码中有不合理的地方，烦请大家指点。