Java數(shù)據(jù)庫連接池
import java.sql.*;
import java.util.*;
import java.io.*;
/**
?*
?* Title:數(shù)據(jù)庫連接池
?*
?*
?* Description:本連接池支持對失效連接重連、重建連接池，并監(jiān)控調(diào)用者及調(diào)用時間
?* 本類需要在類路徑根中存在db.properties數(shù)據(jù)庫配置文件，文件內(nèi)容示例：
?* drivers=net.sourceforge.jtds.jdbc.Driver
?* defaultpoolname.url=jdbc:jtds:sqlserver://192.167.1.107:1433/wapplat;charset=gb2312
?* defaultpoolname.user=sa
?* defaultpoolname.password=lutong
?* defaultpoolname.maxconn=20
?*
?*
?* Copyright: Copyright (c) 2005
?*
?*
?* Company:lutong
?*
?*
?* @author DBoy
?* @version 1.0
?*/
public class ConnectPool extends Thread
{??
??? /* 連接池，存放已創(chuàng)建但未使用的連接 */
??? private Stack pool = new Stack();
??? /* 被返回的數(shù)據(jù)庫連接,將由線程檢測并返回到池中 */
??? private Stack returnedPool = new Stack();
??? /* 已被取走、正在使用的連接 */
??? private Map using = new HashMap();
??? /* 已經(jīng)創(chuàng)建連接池計數(shù) */
??? private int created = 0;
??? /* JDBC Driver類 */
??? String drivers = null;
??? /* 數(shù)據(jù)庫連接字符串 */
??? String url = null;
??? /* 數(shù)據(jù)庫連接用戶名 */
??? String user = null;
??? /* 數(shù)據(jù)庫連接密碼 */
??? String password = null;
??? /* 連接池最大數(shù) */
??? int max = 100;
??? /* 連接池最小數(shù) （還未實現(xiàn)）*/
??? int min = 10;
??? /* 空閑連接等待釋放的時間(秒) ，（還未實現(xiàn)）*/
??? int idleTime = 1800;
???
??? /*是否需要停止線程*/
??? boolean stopThread = false;
??? /*各種同步鎖對象，據(jù)說byte[]對象創(chuàng)建時間最短，占資料最少*/
??? private byte[] createdLock = new byte[0];
??? private byte[] usingLock = new byte[0];
??? private byte[] poolLock = new byte[0];
??? private byte[] returnedPoolLock = new byte[0];
???
??? /*單實例*/
??? private static ConnectPool instance = new ConnectPool();
??? /**
???? * 私有的構造方法，防止從外部直接實例化
???? *?
???? */
??? private ConnectPool()
??? {
??????? /* 初始化數(shù)據(jù)庫連接參數(shù) */
??????? init();
??????? /* 啟動服務線程 */
??????? start();
??? }
??? /**
???? * 從外部取得本類實例的唯一方法
???? *
???? * @return ConnectPool
???? */
??? public static ConnectPool getInstance()
??? {
??????? return instance;
??? }
??? /**
???? * 從連接池中取得一個數(shù)據(jù)庫連接
???? * 如果池中已沒有連接，則新創(chuàng)建一個連接
???? * 被使用的連接放到using對象里
???? * @param caller
???? * @return
???? */
??? public Connection getConnection(String poolname, String caller)
??? {
??????? if(null==caller || caller.length()==0)
??????? {???????????
??????????? StackTraceElement[] callerStackTrace = new Throwable().getStackTrace();
??????????? caller = callerStackTrace[1].toString();
??????? }
??????? Connection conn = null;
??????? try
??????? {
??????????? synchronized(poolLock)
??????????? {
??????????????? conn = (Connection) pool.pop();??
??????????? }
??????? }
??????? catch (EmptyStackException e)
??????? {
??????????? conn = newConnection();
??????? }
??????? if (null != conn)
??????? {
??????????? synchronized(usingLock)
??????????? {
??????????????? using.put(conn, new UsingConnection(conn, caller));
??????????? }
??????? }
??????? return conn;
??? }
??? /**
???? * 創(chuàng)建一個新的數(shù)據(jù)庫連接
???? *
???? * @return
???? */
??? private Connection newConnection()
??? {
??????? Connection conn = null;
??????? try
??????? {
??????????? if (created < max)
??????????? {
??????????????? Class.forName(drivers);
??????????????? conn = DriverManager.getConnection(url, user, password);
??????????????? if (null != conn)
??????????????? {
??????????????????? synchronized(createdLock)
??????????????????? {
??????????????????????? created++;
??????????????????? }
??????????????? }
??????????? }
??????? }
??????? catch (Exception e)
??????? {
??????????? e.printStackTrace();
??????? }
??????? return conn;
??? }
??? /**
???? * 返回一個數(shù)據(jù)庫連接到池中，再由線程返回連接池
???? *
???? * @param conn
???? */
??? public void freeConnection(Connection conn)
??? {
??????? freeConnection(null, conn);
??? }
??? public void freeConnection(String poolName, Connection conn)
??? {
??????? if (null != conn)
??????? {
??????????? synchronized(returnedPoolLock)
??????????? {
??????????????? returnedPool.push(conn);
??????????? }
??????? }
??? }
??? /**
???? * 初始化數(shù)據(jù)庫連接使用的參數(shù)
???? *?
???? */
??? private void init()
??? {
??????? InputStream is = getClass().getResourceAsStream("/db.properties");
??????? Properties dbProps = new Properties();
??????? try
??????? {
??????????? dbProps.load(is);
??????? }
??????? catch (Exception e)
??????? {
??????????? System.err.println("Can't read the properties file. " + "Make sure db.properties is in the CLASSPATH");
??????????? return;
??????? }
??????? drivers = dbProps.getProperty("drivers");
??????? url = dbProps.getProperty("defaultpoolname.url");
??????? user = dbProps.getProperty("defaultpoolname.user");
??????? password = dbProps.getProperty("defaultpoolname.password");
??????? max = Integer.parseInt(dbProps.getProperty("defaultpoolname.maxconn"));???????
??? }
??? /**
???? * 連接服務線程，主要作用： 記錄已取走的連接 測試返回的連接是否可用
???? */
??? public void run()
??? {
??????? Connection conn = null;
??????? UsingConnection uc = null;
??????? while (true? && !stopThread)
??????? {
??????????? /*
???????????? * 處理被返回的數(shù)據(jù)庫連接 判斷連接是否由本池創(chuàng)建并發(fā)出的，如果不是則直接關閉
???????????? * 如果是則測試連接是否有效，無效從池中刪除，有效則返回池中
???????????? */
??????????? while (!returnedPool.empty())
??????????? {
??????????????? synchronized(returnedPoolLock)
??????????????? {
??????????????????? conn = (Connection) returnedPool.pop();
??????????????? }
??????????????? synchronized(usingLock)
??????????????? {
??????????????????? uc = (UsingConnection) using.get(conn);
??????????????? }
??????????????? if (null == uc)
??????????????? {
??????????????????? try
??????????????????? {
??????????????????????? conn.close();
??????????????????? }
??????????????????? catch (Exception e)
??????????????????? {
??????????????????? }
??????????????? }
??????????????? synchronized(usingLock)
??????????????? {
??????????????????? using.remove(conn);
??????????????? }
??????????????? if (testOK(conn))
??????????????? {
??????????????????? synchronized(poolLock)
??????????????????? {
??????????????????????? pool.add(conn);
??????????????????? }
??????????????? }
??????????????? else
??????????????? {
??????????????????? try
??????????????????? {
??????????????????????? conn.close();
??????????????????? }
??????????????????? catch (Exception e)
??????????????????? {
??????????????????? }
??????????????????? synchronized(createdLock)
??????????????????? {
??????????????????????? created--;
??????????????????? }
??????????????? }
??????????? }
??????????? conn = null;
??????????? uc = null;
??????????? /* 避免循環(huán)太快 */
??????????? try
??????????? {
??????????????? Thread.sleep(50);
??????????? }
??????????? catch (InterruptedException ie)
??????????? {
??????????? }
??????? }
??????? stopThread = false;
??? }
??? /**
???? * 測試連接是否正常
???? *
???? * @param conn
???? * @return
???? */
??? public boolean testOK(Connection conn)
??? {
??????? boolean result = false;
??????? PreparedStatement pstmt = null;
??????? ResultSet rs = null;
??????? try
??????? {
??????????? pstmt = conn.prepareStatement("select 1");
??????????? rs = pstmt.executeQuery();
??????????? result = true;
??????? }
??????? catch (Exception e)
??????? {
??????? }
??????? finally
??????? {
??????????? if (null != rs)
??????????? {
??????????????? try
??????????????? {
??????????????????? rs.close();
??????????????? }
??????????????? catch (Exception e)
??????????????? {
??????????????? }
??????????? }
??????????? if (null != pstmt)
??????????? {
??????????????? try
??????????????? {
??????????????????? pstmt.close();
??????????????? }
??????????????? catch (Exception e)
??????????????? {
??????????????? }
??????????? }
??????? }
??????? return result;
??? }
??? /**
???? * 取得當前正使用的連接信息（HTML格式）
???? *
???? * @return
???? */
??? public String getUsingHTMLInfo()
??? {
??????? StringBuffer info = new StringBuffer();
??????? info.append("Driver:" + drivers + "
");
??????? info.append("Connect url:" + url + "
");
??????? synchronized(createdLock)
??????? {
??????????? info.append("Created connection count:" + created + "
");
??????? }
??????? synchronized(usingLock)
??????? {
???????? info.append("Using connection count:" + using.values().size() + "
");
???????? info.append("
| Caller | Using Time(ms) |
| "); ???????????? info.append(uc.getCaller()); ???????????? info.append(" | "); ???????????? info.append(uc.getUsingTime()); ???????????? info.append(" |
??????? return info.toString();
??? }
??? /**
???? * 釋放所有連接,創(chuàng)建新池
???? */
??? public void release()
??? {??
??????? /*要求停止線程*/
??????? stopThread = true;
???????
??????? /*停等待線程結(jié)束,線程結(jié)束時會把stopThread置為false*/
??????? int timeout = 0;
??????? while(stopThread)
??????? {??
??????????? if(++timeout>600)
??????????? {
??????????????? break;
??????????? }
??????????? try
??????????? {
??????????????? Thread.sleep(1000);
??????????? }
??????????? catch (InterruptedException ie)
??????????? {
??????????? }
??????? }
???????
??????? /*創(chuàng)建新連接池實例*/
??????? instance = new ConnectPool();
???????
??????? /*釋放所有連接，除了Using，Using是正在使用的且會在新的池里被釋放*/
??????? synchronized(poolLock)
??????? {
???????? while(!pool.isEmpty())
???????? {??
???????????? try
???????????? {
???????????????? Connection conn = (Connection)pool.pop();
???????????????? conn.close();
???????????? }
???????????? catch(Exception e)
???????????? {???????????????
???????????? }
???????? }
??????? }
????
??????? synchronized(returnedPoolLock)
??????? {
???????? while(!returnedPool.isEmpty())
???????? {??
???????????? try
???????????? {
???????????????? Connection conn = (Connection)returnedPool.pop();
???????????????? conn.close();
???????????? }
???????????? catch(Exception e)
???????????? {???????????????
???????????? }
???????? }
??????? }
??? }
}
/**
?* 用戶存儲當前被使用的數(shù)據(jù)庫連接信息
?*/
class UsingConnection
{
??? private Connection conn = null;
??? private String caller = null;
??? long time = 0;
??? public UsingConnection(Connection conn, String caller)
??? {
??????? this.conn = conn;
??????? this.caller = caller;
??????? time = System.currentTimeMillis();
??? }
??? public String getCaller()
??? {
??????? return caller;
??? }
??? public long getUsingTime()
??? {
??????? return System.currentTimeMillis() - time;
??? }
}
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