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jsp中实现连接池



作者:未知    文章来源:www.jspcn.net
发布日期:2005年01月19日
在JSP里有两种实现的办法,一种是用JNDI(Java Naming Directory Interface),这可能和应用服务器有关,如果是Resin,先在resin.conf里定义
<resource-ref>
<res-ref-name>jdbc/oracle</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<init-param driver-name="oracle.jdbc.driver.OracleDriver"/>
<init-param url="jdbc:oracle:thin:@192.168.1.1:1521:oracle"/>
<init-param user="system"/>
<init-param password="manager"/>
<init-param max-connections="20"/>
<init-param max-idle-time="30"/>
</resource-ref>
如果为Tomcat,在Server.xml里面定义,有关的资料可以查文档,然后在jsp里这样用
try{
javax.naming.Context env = (Context)new InitialContext().lookup("java:comp/env");
javax.sql.DataSource pool=(javax.sql.DataSource) env.lookup("jdbc/oracle");
}catch(Exception e){System.err.println("Exception error:"+e.getMessage());}

try {
Connection conn = pool.getConnection();
}catch(Exception e){System.out.println("Exception error:"+e.getMessage());}
通过这段代码,你就获得从连接池里获得了一个连接conn。如果想用普通的连接池,那只能用JavaBean了,先写一个ConnectionPool的java的类,然后直接从连接池中获得连接,下面是我一个连接池的JavaBean
ConnectionPool.java如下:

import java.io.PrintStream;
import java.sql.Connection;
import java.util.Vector;

// Referenced classes of package com.ilovejsp.sql:
// DataSource, PooledConnection

public class ConnectionPool
{
private Vector pool;
private int size;
DataSource db;

public ConnectionPool()
{
pool = null;
size = 0;
db = new DataSource();
}

public void setSize(int value)
{
if(value > 1)
size = value;
}

public int getSize()
{
return size;
}

public synchronized void initPool()
throws Exception
{
try
{
for(int x = 0; x < size; x++)
{
Connection conn = db.getConnection();
if(conn != null)
{
PooledConnection pcon = new PooledConnection(conn);
addConnection(pcon);
}
}

}
catch(Exception e)
{
System.err.println(e.getMessage());
}
}

private void addConnection(PooledConnection pcon)
{
if(pool == null)
pool = new Vector(size);
pool.addElement(pcon);
}

public synchronized void releaseConnection(Connection conn)
{
int x = 0;
do
{
if(x >= pool.size())
break;
PooledConnection pcon = (PooledConnection)pool.elementAt(x);
if(pcon.getConnection() == conn)
{
System.err.println("Release Connection".concat(String.valueOf(String.valueOf(x))));
pcon.setInUse(false);
break;
}
x++;
}
while(true);
}

public synchronized Connection getConnection()
throws Exception
{
PooledConnection pcon = null;
for(int x = 0; x < pool.size(); x++)
{
pcon = (PooledConnection)pool.elementAt(x);
if(!pcon.inUse())
{
pcon.setInUse(true);
return pcon.getConnection();
}
}

try
{
Connection conn = db.getConnection();
pcon = new PooledConnection(conn);
pcon.setInUse(true);
pool.addElement(pcon);
}
catch(Exception e)
{
System.err.println("Exception error:".concat(String.valueOf(String.valueOf(e.getMessage()))));
}
return pcon.getConnection();
}

public synchronized void emptyPool()
{
for(int x = 0; x < pool.size(); x++)
{
System.err.println("Closing Jdbc Connection".concat(String.valueOf(String.valueOf(x))));
PooledConnection pcon = (PooledConnection)pool.elementAt(x);
if(!pcon.inUse())
{
pcon.close();
continue;
}
try
{
Thread.sleep(3000L);
pcon.close();
}
catch(Exception e)
{
System.out.println("Exception :".concat(String.valueOf(String.valueOf(e.getMessage()))));
}
}

db.close();
}
}
testpool.jsp内容如下:
<%@ page language="java" contentType="text/html;charset=gb2312"%>
<%@ page import="java.sql.*"%>

<HTML>
<HEAD>
<TITLE>系统数据信息</TITLE>
</HEAD>
<BODY>
<%ConnectionPool db=new ConnectionPool();
Connection conn=db.getConnection();
Statement stmt=conn.createStatement();
String sql1="select * from pg_database ";

ResultSet rs=stmt.executeQuery(sql1);
%>
<TABLE><TR><TD>系统数据库信息</TD></TR>
<TR><TD>
<%while(rs.next()) {
%>
<%=rs.getString(1)%>
<%}
rs.close();%>
</TR></TD>
<TABLE><TR><TD>系统字段信息</TD></TR>
<TR><TD>
<%String sql2="select * from pg_type";
rs=stmt.executeQuery(sql2);
while(rs.next()) {
%>
(<%=rs.getString(1)%>)
<%}
rs.close();
db.close();%>
</TR></TD>
</BODY>
</HTML>
 
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