因為工作需要要使用到連接池，所以拜讀了互聯網上眾多前輩的文章，學了不少經驗，這裡想做一個小結，加上自己的想法和在一起，希望能給大家一些幫助。
目的：消除數據庫頻繁連接帶來的開銷和瓶頸。
解決方案：不過多的限制用戶的使用，既不能太多的要求用戶按規定的方法得到和使用數據庫連盡量保持用戶的習慣
目前的很多方法都是要求用戶只能按規定方法使用連接，不能使用直接關閉數據連接的方法。解決辦法就是使用代理類，來中間解決。可以參考http://www-900.ibm.com/developerWorks/cn/java/l-connpoolproxy/index.shtml
能維護連接的正常狀態
因為針對數據庫連接創建的資源，如果不能及時的釋放，就會影響下一次數據連接的使用。例如在sql 2k中，一個連接不同創建多條Statement否則操作時會有數據連接占線的異常，所以必須在歸還連接以後釋放這些資源。
//判斷是使用了createStatement語句
if (CREATESTATE.equals(method.getName()))
{
obj = method.invoke(conn, args);
statRef = (Statement)obj;//記錄語句
return obj;
}//判斷是否調用了close的方法，如果調用close方法則把連接置為無用狀態正確保護類不被違例使用
if(CLOSE.equals(method.getName()))
{
//設置不使用標志
setIsFree(false);
//檢查是否有後續工作，清除該連接無用資源
if (statRef != null)
statRef.close();
if (prestatRef != null)
prestatRef.close();
return null;
}
一個考慮就是不能讓用戶隨便使用代理類，而只能自己使用，一個就是用內部私有類，一個就是使用只有指定類才能調用的標志。我的實現就是采用後者。
/**
* 創建連接的工廠，只能讓工廠調用
* @param factory 要調用工廠，並且一定被正確初始化
* @param param 連接參數
* @return 連接
*/
static public _Connection getConnection(ConnectionFactory factory, ConnectionParam param)
{
if (factory.isCreate())//判斷是否正確初始化的工廠
{
_Connection _conn = new _Connection(param);
return _conn;
}
else
return null;
}
提供良好的用戶接口，簡單實用
使用靜態方法創建工廠，然後來得到連接，使用完全和普通的Connection方法一樣，沒有限制。同時為了方便，設置了連接參數類和工廠參數類。
ConnectionParam param = new ConnectionParam(driver,url,user,password);
ConnectionFactory cf = null;//new ConnectionFactory(param, new FactoryParam());
try{
cf = new ConnectionFactory(param,new FactoryParam());
Connection conn1 = cf.getFreeConnection();
Connection conn2 = cf.getFreeConnection();
Connection conn3 = cf.getFreeConnection();
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn1 y");
}
else
{
System.out.println("conn1 n");
}
stmt.close();
conn1.close();
為了實現連接池的正常運作，使用了單態模/**
* 使用指定的參數創建一個連接池
*/
public ConnectionFactory(ConnectionParam param, FactoryParam fparam)
throws SQLException
{
//不允許參數為空
if ((param == null)||(fparam == null))
throw new SQLException("ConnectionParam和FactoryParam不能為空");
if (m_instance == null)
{
synchronized(ConnectionFactory.class){
if (m_instance == null)
{
//new instance
//參數定制
m_instance = new ConnectionFactory();
m_instance.connparam = param;
m_instance.MaxConnectionCount = fparam.getMaxConn();
m_instance.MinConnectionCount = fparam.getMinConn();
m_instance.ManageType = fparam.getType();
m_instance.isflag = true;
//初始化，創建MinConnectionCount個連接
System.out.println("connection factory 創建！");
try{
for (int i=0; i < m_instance.MinConnectionCount; i++)
{
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam);
if (_conn == null) continue;
System.out.println("connection創建");
m_instance.FreeConnectionPool.add(_conn);//加入空閒連接池
m_instance.current_conn_count ++;
//標志是否支持事務
m_instance.supportTransaction = _conn.isSupportTransaction();
}
}
catch(Exception e)
{
e.printStackTrace();
}
//根據策略判斷是否需要查詢
if (m_instance.ManageType != 0)
{
Thread t = new Thread(new FactoryMangeThread(m_instance));
t.start();
}
}
}
}
}
連接池的管理
對於連接池的管理，我是設想使用靜態管理和動態管理兩種策略，設置了最大限制，和恆定的連接數。使用了2個池，一個空閒池，一個使用池。靜態就是使用的時候發現空閒連接不夠再去檢查。動態就是使用了一個線程定時檢查。
//根據策略判斷是否需要查詢
if (m_instance.ManageType != 0)
{
Thread t = new Thread(new FactoryMangeThread(m_instance));
t.start();
}
//連接池調度線程
public class FactoryMangeThread implements Runnable {
ConnectionFactory cf = null;
long delay = 1000;
public FactoryMangeThread(ConnectionFactory obj)
{
cf = obj;
}
/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run() {
while(true){
try{
Thread.sleep(delay);
}
catch(InterruptedException e){}
System.out.println("eeeee");
//判斷是否已經關閉了工廠，那就退出監聽
if (cf.isCreate())
cf.schedule();
else
System.exit(1);
}
}
}
最後給出完整的源代碼：
_Connectio.java
package scut.ailab.connectionpool;
import java.lang.reflect.*;
import java.sql.*;
/**
* @author youyongming
* 定義數據庫連接的代理類
*/
public class _Connection implements InvocationHandler {
//定義連接
private Connection conn = null;
//定義監控連接創建的語句
private Statement statRef = null;
private PreparedStatement prestatRef = null;
//是否支持事務標志
private boolean supportTransaction = false;
//數據庫的忙狀態
private boolean isFree = false;
//最後一次訪問時間
long lastAccessTime = 0;
//定義要接管的函數的名字
String CREATESTATE = "createStatement";
String CLOSE = "close";
String PREPARESTATEMENT = "prepareStatement";
String COMMIT = "commit";
String ROLLBACK = "rollback";
/**
* 構造函數，采用私有，防止被直接創建
* @param param 連接參數
*/
private _Connection(ConnectionParam param) {
//記錄日至
try{
//創建連接
Class.forName(param.getDriver()).newInstance();
conn = DriverManager.getConnection(param.getUrl(),param.getUser(), param.getPassword());
DatabaseMetaData dm = null;
dm = conn.getMetaData();
//判斷是否支持事務
supportTransaction = dm.supportsTransactions();
}
catch(Exception e)
{
e.printStackTrace();
}
}
/* (non-Javadoc)
* @see java.lang.reflect.InvocationHandler#invoke
*(java.lang.Object, java.lang.reflect.Method, java.lang.Object[])
*/
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
Object obj = null;
//判斷是否調用了close的方法，如果調用close方法則把連接置為無用狀態
if(CLOSE.equals(method.getName()))
{
//設置不使用標志
setIsFree(false);
//檢查是否有後續工作，清除該連接無用資源
if (statRef != null)
statRef.close();
if (prestatRef != null)
prestatRef.close();
return null;
}
//判斷是使用了createStatement語句
if (CREATESTATE.equals(method.getName()))
{
obj = method.invoke(conn, args);
statRef = (Statement)obj;//記錄語句
return obj;
}
//判斷是使用了prepareStatement語句
if (PREPARESTATEMENT.equals(method.getName()))
{
obj = method.invoke(conn, args);
prestatRef = (PreparedStatement)obj;
return obj;
}
//如果不支持事務，就不執行該事物的代碼
if ((COMMIT.equals(method.getName())||ROLLBACK.equals(method.getName()))
&& (!isSupportTransaction()))
return null;
obj = method.invoke(conn, args);
//設置最後一次訪問時間，以便及時清除超時的連接
lastAccessTime = System.currentTimeMillis();
return obj;
}
/**
* 創建連接的工廠，只能讓工廠調用
* @param factory 要調用工廠，並且一定被正確初始化
* @param param 連接參數
* @return 連接
*/
static public _Connection getConnection(ConnectionFactory factory, ConnectionParam param)
{
if (factory.isCreate())//判斷是否正確初始化的工廠
{
_Connection _conn = new _Connection(param);
return _conn;
}
else
return null;
}
public Connection getFreeConnection() {
//返回數據庫連接conn的接管類，以便截住close方法
Connection conn2 = (Connection)Proxy.newProxyInstance(
conn.getClass().getClassLoader(),
conn.getClass().getInterfaces(),this);
return conn2;
}
/**
* 該方法真正的關閉了數據庫的連接
* @throws SQLException
*/
void close() throws SQLException{
//由於類屬性conn是沒有被接管的連接，因此一旦調用close方法後就直接關閉連接
conn.close();
}
public void setIsFree(boolean value)
{
isFree = value;
}
public boolean isFree() {
return isFree;
}
/**
* 判斷是否支持事務
* @return boolean
*/
public boolean isSupportTransaction() {
return supportTransaction;
}
}
ConnectionFactory.java
package scut.ailab.connectionpool;
/**
* @author youyongming
*
*/
import java.util.LinkedHashSet;
import java.sql.*;
import java.util.Iterator;
public class ConnectionFactory {
private static ConnectionFactory m_instance = null;
//在使用的連接池
private LinkedHashSet ConnectionPool = null;
//空閒連接池
private LinkedHashSet FreeConnectionPool = null;
//最大連接數
private int MaxConnectionCount = 4;
//最小連接數
private int MinConnectionCount = 2;
//當前連接數
private int current_conn_count = 0;
//連接參數
private ConnectionParam connparam = null;
//是否創建工廠的標志
private boolean isflag = false;
//是否支持事務
private boolean supportTransaction = false;
//定義管理策略
private int ManageType = 0;
private ConnectionFactory(){
ConnectionPool = new LinkedHashSet();
FreeConnectionPool = new LinkedHashSet();
}
/**
* 使用指定的參數創建一個連接池
*/
public ConnectionFactory(ConnectionParam param, FactoryParam fparam)
throws SQLException
{
//不允許參數為空
if ((param == null)||(fparam == null))
throw new SQLException("ConnectionParam和FactoryParam不能為空");
if (m_instance == null)
{
synchronized(ConnectionFactory.class){
if (m_instance == null)
{
//new instance
//參數定制
m_instance = new ConnectionFactory();
m_instance.connparam = param;
m_instance.MaxConnectionCount = fparam.getMaxConn();
m_instance.MinConnectionCount = fparam.getMinConn();
m_instance.ManageType = fparam.getType();
m_instance.isflag = true;
//初始化，創建MinConnectionCount個連接
System.out.println("connection factory 創建！");
try{
for (int i=0; i < m_instance.MinConnectionCount; i++)
{
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam);
if (_conn == null) continue;
System.out.println("connection創建");
m_instance.FreeConnectionPool.add(_conn);//加入空閒連接池
m_instance.current_conn_count ++;
//標志是否支持事務
m_instance.supportTransaction = _conn.isSupportTransaction();
}
}
catch(Exception e)
{
e.printStackTrace();
}
//根據策略判斷是否需要查詢
if (m_instance.ManageType != 0)
{
Thread t = new Thread(new FactoryMangeThread(m_instance));
t.start();
}
}
}
}
}
/**
* 標志工廠是否已經創建
* @return boolean
*/
public boolean isCreate()
{
return m_instance.isflag;
}
/**
* 從連接池中取一個空閒的連接
* @return Connection
* @throws SQLException
*/
public synchronized Connection getFreeConnection()
throws SQLException
{
Connection conn = null;
//獲取空閒連接
Iterator iter = m_instance.FreeConnectionPool.iterator();
while(iter.hasNext()){
_Connection _conn = (_Connection)iter.next();
//找到未用連接
if(!_conn.isFree()){
conn = _conn.getFreeConnection();
_conn.setIsFree(true);
//移出空閒區
m_instance.FreeConnectionPool.remove(_conn);
//加入連接池
m_instance.ConnectionPool.add(_conn);
break;
}
}
//檢查空閒池是否為空
if (m_instance.FreeConnectionPool.isEmpty())
{
//再檢查是否能夠分配
if (m_instance.current_conn_count < m_instance.MaxConnectionCount)
{
//新建連接到空閒連接池
int newcount = 0 ;
//取得要建立的數目
if (m_instance.MaxConnectionCount - m_instance.current_conn_count >=
m_instance.MinConnectionCount)
{
newcount = m_instance.MinConnectionCount;
}
else
{
newcount = m_instance.MaxConnectionCount - m_instance.current_conn_count;
}
//創建連接
for (int i=0;i <newcount; i++)
{
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam);
m_instance.FreeConnectionPool.add(_conn);
m_instance.current_conn_count ++;
}
}
else
{//如果不能新建，檢查是否有已經歸還的連接
iter = m_instance.ConnectionPool.iterator();
while(iter.hasNext()){
_Connection _conn = (_Connection)iter.next();
if(!_conn.isFree()){
conn = _conn.getFreeConnection();
_conn.setIsFree(false);
m_instance.ConnectionPool.remove(_conn);
m_instance.FreeConnectionPool.add(_conn);
break;
}
}
}
}//if (FreeConnectionPool.isEmpty())
//再次檢查是否能分配連接
if(conn == null){
iter = m_instance.FreeConnectionPool.iterator();
while(iter.hasNext()){
_Connection _conn = (_Connection)iter.next();
if(!_conn.isFree()){
conn = _conn.getFreeConnection();
_conn.setIsFree(true);
m_instance.FreeConnectionPool.remove(_conn);
m_instance.ConnectionPool.add(_conn);
break;
}
}
if(conn == null)//如果不能則說明無連接可用
throw new SQLException("沒有可用的數據庫連接");
}
System.out.println("get connection");
return conn;
}
/**
* 關閉該連接池中的所有數據庫連接
* @throws SQLException
*/
public synchronized void close() throws SQLException
{
this.isflag = false;
SQLException excp = null;
//關閉空閒池
Iterator iter = m_instance.FreeConnectionPool.iterator();
while(iter.hasNext()){
try{
((_Connection)iter.next()).close();
System.out.println("close connection:free");
m_instance.current_conn_count --;
}catch(Exception e){
if(e instanceof SQLException)
excp = (SQLException)e;
}
}
//關閉在使用的連接池
iter = m_instance.ConnectionPool.iterator();
while(iter.hasNext()){
try{
((_Connection)iter.next()).close();
System.out.println("close connection:inused");
m_instance.current_conn_count --;
}catch(Exception e){
if(e instanceof SQLException)
excp = (SQLException)e;
}
}
if(excp != null)
throw excp;
}
/**
* 返回是否支持事務
* @return boolean
*/
public boolean isSupportTransaction() {
return m_instance.supportTransaction;
}
/**
* 連接池調度管理
*
*/
public void schedule()
{
Connection conn = null;
//再檢查是否能夠分配
Iterator iter = null;
//檢查是否有已經歸還的連接
{
iter = m_instance.ConnectionPool.iterator();
while(iter.hasNext()){
_Connection _conn = (_Connection)iter.next();
if(!_conn.isFree()){
conn = _conn.getFreeConnection();
_conn.setIsFree(false);
m_instance.ConnectionPool.remove(_conn);
m_instance.FreeConnectionPool.add(_conn);
break;
}
}
}
if (m_instance.current_conn_count < m_instance.MaxConnectionCount)
{
//新建連接到空閒連接池
int newcount = 0 ;
//取得要建立的數目
if (m_instance.MaxConnectionCount - m_instance.current_conn_count
>=m_instance.MinConnectionCount)
{
newcount = m_instance.MinConnectionCount;
}
else
{
newcount = m_instance.MaxConnectionCount - m_instance.current_conn_count;
}
//創建連接
for (int i=0;i <newcount; i++)
{
_Connection _conn = _Connection.getConnection(m_instance, m_instance.connparam);
m_instance.FreeConnectionPool.add(_conn);
m_instance.current_conn_count ++;
}
}
}
}
ConnectionParam.javapackage scut.ailab.connectionpool;
import java.io.Serializable;
/**
* @author youyongming
* 實現數據庫連接的參數類
*/
public class ConnectionParam implements Serializable {
private String driver; //數據庫驅動程序
private String url; //數據連接的URL
private String user; //數據庫用戶名
private String password; //數據庫密碼
/**
* 唯一的構造函數，需要指定連接的四個必要參數
* @param driver數據驅動
* @param url 數據庫連接url
* @param user 用戶名
* @param password密碼
*/
public ConnectionParam(String driver,String url,String user,String password)
{
this.driver = driver;
this.url = url;
this.user = user;
this.password = password;
}
public String getDriver() {
return driver;
}
public String getPassword() {
return password;
}
public String getUrl() {
return url;
}
public String getUser() {
return user;
}
public void setDriver(String driver) {
this.driver = driver;
}
public void setPassword(String password) {
this.password = password;
}
public void setUrl(String url) {
this.url = url;
}
public void setUser(String user) {
this.user = user;
}
/**
* @see java.lang.Object#clone()
*/
public Object clone(){
ConnectionParam param = new ConnectionParam(driver,url,user,password);
return param;
}
/**
* @see java.lang.Object#equals(java.lang.Object)
*/
public boolean equals(Object obj) {
if(obj instanceof ConnectionParam){
ConnectionParam param = (ConnectionParam)obj;
return ((driver.compareToIgnoreCase(param.getDriver()) == 0)&&
(url.compareToIgnoreCase(param.getUrl()) == 0)&&
(user.compareToIgnoreCase(param.getUser()) == 0)&&
(password.compareToIgnoreCase(param.getPassword()) == 0));
}
return false;
}
}
FactoryMangeThread.java
/*
* Created on 2003-5-13
*
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
package scut.ailab.connectionpool;
/**
* @author youyongming
*
*/
//連接池調度線程
public class FactoryMangeThread implements Runnable {
ConnectionFactory cf = null;
long delay = 1000;
public FactoryMangeThread(ConnectionFactory obj)
{
cf = obj;
}
/* (non-Javadoc)
* @see java.lang.Runnable#run()
*/
public void run() {
while(true){
try{
Thread.sleep(delay);
}
catch(InterruptedException e){}
System.out.println("eeeee");
//判斷是否已經關閉了工廠，那就退出監聽
if (cf.isCreate())
cf.schedule();
else
System.exit(1);
}
}
}
FactoryParam.java
/*
* Created on 2003-5-13
*
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
package scut.ailab.connectionpool;
/**
* @author youyongming
*
*/
//連接池工廠參數
public class FactoryParam {
//最大連接數
private int MaxConnectionCount = 4;
//最小連接數
private int MinConnectionCount = 2;
//回收策略
private int ManageType = 0;
public FactoryParam(){
}
/**
* 構造連接池工廠參數的對象
* @param max最大連接數
* @param min最小連接數
* @param type管理策略
*/
public FactoryParam(int max, int min, int type)
{
this.ManageType = type;
this.MaxConnectionCount = max;
this.MinConnectionCount = min;
}
/**
* 設置最大的連接數
* @param value
*/
public void setMaxConn(int value)
{
this.MaxConnectionCount = value;
}
/**
* 獲取最大連接數
* @return
*/
public int getMaxConn()
{
return this.MaxConnectionCount;
}
/**
* 設置最小連接數
* @param value
*/
public void setMinConn(int value)
{
this.MinConnectionCount = value;
}
/**
* 獲取最小連接數
* @return
*/
public int getMinConn()
{
return this.MinConnectionCount;
}
public int getType()
{
return this.ManageType;
}
}
testmypool.java
/*
* Created on 2003-5-13
*
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
package scut.ailab.connectionpool;
/**
* @author youyongming
*
*/
import java.sql.*;
public class testmypool {
public void test1()
{
String user = "DevTeam";
String password = "DevTeam";
String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
String url = "jdbc:odbc:gfqh2";
ConnectionParam param = new ConnectionParam(driver,url,user,password);
ConnectionFactory cf = null;//new ConnectionFactory(param, new FactoryParam());
try{
cf = new ConnectionFactory(param,new FactoryParam());
Connection conn1 = cf.getFreeConnection();
Connection conn2 = cf.getFreeConnection();
Connection conn3 = cf.getFreeConnection();
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn1 y");
}
else
{
System.out.println("conn1 n");
}
stmt.close();
conn1.close();
Connection conn4 = cf.getFreeConnection();
Connection conn5 = cf.getFreeConnection();
stmt = conn5.createStatement();
rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn5 y");
}
else
{
System.out.println("conn5 n");
}
conn2.close();
conn3.close();
conn4.close();
conn5.close();
}
catch(Exception e)
{
e.printStackTrace();
}
finally{
try{
cf.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
public static void main(String[] args) {
String user = "DevTeam";
String password = "DevTeam";
String driver = "sun.jdbc.odbc.JdbcOdbcDriver";
String url = "jdbc:odbc:gfqh2";
ConnectionParam param = new ConnectionParam(driver,url,user,password);
ConnectionFactory cf = null;//new ConnectionFactory(param,new FactoryParam());
try{
cf = new ConnectionFactory(param,new FactoryParam());
ConnectionFactory cf1= new ConnectionFactory(param,new FactoryParam());
Connection conn1 = null;
long time = System.currentTimeMillis();
for (int i=0; i <10;i++)
{
conn1 = cf.getFreeConnection();
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn1 y");
}
else
{
System.out.println("conn1 n");
}
conn1.close();
}
System.out.println("pool:" + (System.currentTimeMillis()-time));
time = System.currentTimeMillis();
Class.forName(param.getDriver()).newInstance();
for (int i=0; i <10;i++)
{
conn1 = DriverManager.getConnection(param.getUrl(),
param.getUser(), param.getPassword());
Statement stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery("select * from requests");
if (rs.next())
{
System.out.println("conn1 y");
}
else
{
System.out.println("conn1 n");
}
conn1.close();
}
System.out.println("no pool:" + (System.currentTimeMillis()-time));
}
catch(Exception e)
{
e.printStackTrace();
}
finally{
try{
cf.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
}
