jsp中实现连接池

2005-3-20 7:48:34　　作者：模板天下收集整理　　来源：未知　网友评论 0 条　论坛

　　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

jdbc/oracle
javax.sql.DataSource







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.*"%>






<%ConnectionPool db=new ConnectionPool();
Connection conn=db.getConnection();
Statement stmt=conn.createStatement();
String sql1="select * from pg_database ";

ResultSet rs=stmt.executeQuery(sql1);
%>

系统数据库信息

<%while(rs.next()) { %> <%=rs.getString(1)%> <%} rs.close();%>

系统字段信息

<%String sql2="select * from pg_type"; rs=stmt.executeQuery(sql2); while(rs.next()) { %> (<%=rs.getString(1)%>) <%} rs.close(); db.close();%>

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