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javaBean數據庫連接池

/**

?*? @author ?zhupan(溫柔一刀)?Creation?date:?06-10-2006

? */

package ?com.zhupan.StrutsArticle.Utils;

import ?java.sql.Connection;

public ? class ?DBConnection? {

? public ? static ? synchronized ?Connection?getConnection()? throws ?Exception? {??

??Connection?conn? = ? null ;

??DBConnectionManager?dbc;

?? try ? {

???dbc? = ?DBConnectionManager.getInstance();

???conn? = ?dbc.getConnection( " idb " );

??} ? catch ?(Exception?e)? {

??}

?? return ?conn;??

??}

}

/**

?*? @author ?zhupan(溫柔一刀)??Creation?date:?05-01-2006

? */

package ?com.zhupan.StrutsArticle.Utils;

import ?java.io.FileWriter;

import ?java.io.IOException;

import ?java.io.InputStream;

import ?java.io.PrintWriter;

import ?java.sql.Connection;

import ?java.sql.Driver;

import ?java.sql.DriverManager;

import ?java.sql.SQLException;

import ?java.util.Date;

import ?java.util.Enumeration;

import ?java.util.Hashtable;

import ?java.util.Properties;

import ?java.util.StringTokenizer;

import ?java.util.Vector;

/** 連接池

?*?管理類DBConnectionManager支持對一個或多個由屬性文件定義的數據庫連接

?*?池的訪問.客戶程序可以調用getInstance()方法訪問本類的唯一實例.

? */

public ? class ?DBConnectionManager? {

?? static ? private ?DBConnectionManager?instance;? // ?唯一實例

?? static ? private ? int ?clients;

?? private ?Vector?drivers? = ? new ?Vector();

?? private ?PrintWriter?log;

?? private ?Hashtable?pools? = ? new ?Hashtable();

?? /**

???*?返回唯一實例.如果是第一次調用此方法,則創建實例

???*

???*? @return ?DBConnectionManager?唯一實例

??? */

?? static ? synchronized ? public ?DBConnectionManager?getInstance()? {

???? if ?(instance? == ? null )? {

??????instance? = ? new ?DBConnectionManager();

????}

????clients ++ ;

???? return ?instance;

??}

?? /**

???*?建構函數私有以防止其它對象創建本類實例

??? */

?? private ?DBConnectionManager()? {

????init();

??}

?? /**

???*?將連接對象返回給由名字指定的連接池

???*

???*? @param ?name?在屬性文件中定義的連接池名字

???*? @param ?con?連接對象

??? */

?? public ? void ?freeConnection(String?name,?Connection?con)? {

????DBConnectionPool?pool? = ?(DBConnectionPool)?pools.get(name);

???? if ?(pool? != ? null )? {

??????pool.freeConnection(con);

????}

??}

?? /**

???*?獲得一個可用的(空閑的)連接.如果沒有可用連接,且已有連接數小于最大連接數

???*?限制,則創建并返回新連接

???*

???*? @param ?name?在屬性文件中定義的連接池名字

???*? @return ?Connection?可用連接或null

??? */

?? public ?Connection?getConnection(String?name)? {

????DBConnectionPool?pool? = ?(DBConnectionPool)?pools.get(name);

???? if ?(pool? != ? null )? {

?????? return ?pool.getConnection();

????}

???? return ? null ;

??}

?? /**

???*?獲得一個可用連接.若沒有可用連接,且已有連接數小于最大連接數限制,

???*?則創建并返回新連接.否則,在指定的時間內等待其它線程釋放連接.

???*

???*? @param ?name?連接池名字

???*? @param ?time?以毫秒計的等待時間

???*? @return ?Connection?可用連接或null

??? */

?? public ?Connection?getConnection(String?name,? long ?time)? {

????DBConnectionPool?pool? = ?(DBConnectionPool)?pools.get(name);

???? if ?(pool? != ? null )? {

?????? return ?pool.getConnection(time);

????}

???? return ? null ;

??}

?? /**

???*?關閉所有連接,撤銷驅動程序的注冊

??? */

?? public ? synchronized ? void ?release()? {

// ?等待直到最后一個客戶程序調用

???? if ?( -- clients? != ? 0 )? {

?????? return ;

????}

????Enumeration?allPools? = ?pools.elements();

???? while ?(allPools.hasMoreElements())? {

??????DBConnectionPool?pool? = ?(DBConnectionPool)?allPools.nextElement();

??????pool.release();

????}

????Enumeration?allDrivers? = ?drivers.elements();

???? while ?(allDrivers.hasMoreElements())? {

??????Driver?driver? = ?(Driver)?allDrivers.nextElement();

?????? try ? {

????????DriverManager.deregisterDriver(driver);

????????log( " 撤銷JDBC驅動程序? " ? + ?driver.getClass().getName() + " 的注冊 " );

??????}

?????? catch ?(SQLException?e)? {

????????log(e,? " 無法撤銷下列JDBC驅動程序的注冊:? " ? + ?driver.getClass().getName());

??????}

????}

??}

?? /**

???*?根據指定屬性創建連接池實例.

???*

???*? @param ?props?連接池屬性(溫柔一刀)?

??? */

?? private ? void ?createPools(Properties?props)? {

????Enumeration?propNames? = ?props.propertyNames();

???? while ?(propNames.hasMoreElements())? {

??????String?name? = ?(String)?propNames.nextElement();

?????? if ?(name.endsWith( " .url " ))? {

????????String?poolName? = ?name.substring( 0 ,?name.lastIndexOf( " . " ));

????????String?url? = ?props.getProperty(poolName? + ? " .url " );

???????? if ?(url? == ? null )? {

??????????log( " 沒有為連接池 " ? + ?poolName? + ? " 指定URL " );

?????????? continue ;

????????}

????????String?user? = ?props.getProperty(poolName? + ? " .user " );

????????String?password? = ?props.getProperty(poolName? + ? " .password " );

????????String?maxconn? = ?props.getProperty(poolName? + ? " .maxconn " ,? " 0 " );

???????? int ?max;

???????? try ? {

??????????max? = ?Integer.valueOf(maxconn).intValue();

????????}

???????? catch ?(NumberFormatException?e)? {

??????????log( " 錯誤的最大連接數限制:? " ? + ?maxconn? + ? " ?.連接池:? " ? + ?poolName);

??????????max? = ? 0 ;

????????}

????????DBConnectionPool?pool? =

???????????? new ?DBConnectionPool(poolName,?url,?user,?password,?max);

????????pools.put(poolName,?pool);

????????log( " 成功創建連接池 " ? + ?poolName);

??????}

????}

??}

?? /**

???*?讀取屬性完成初始化(溫柔一刀)?

??? */

?? private ? void ?init()? {

????InputStream?is? = ?getClass().getResourceAsStream( " db.properties " );

????Properties?dbProps? = ? new ?Properties();

???? try ? {

??????dbProps.load(is);

????}

???? catch ?(Exception?e)? {

??????System.err.println( " 不能讀取屬性文件.? " ? +

????????????????????????? " 請確保db.properties在CLASSPATH指定的路徑中 " );

?????? return ;

????}

????String?logFile? = ?dbProps.getProperty( " logfile " ,? " DBConnectionManager.log " );

???? try ? {

??????log? = ? new ?PrintWriter( new ?FileWriter(logFile,? true ),? true );

????}

???? catch ?(IOException?e)? {

??????System.err.println( " 無法打開日志文件:? " ? + ?logFile);

??????log? = ? new ?PrintWriter(System.err);

????}

????loadDrivers(dbProps);

????createPools(dbProps);

??}

?? /**

???*?裝載和注冊所有JDBC驅動程序(溫柔一刀)?

???*

???*? @param ?props?屬性

??? */

?? private ? void ?loadDrivers(Properties?props)? {

????String?driverClasses? = ?props.getProperty( " drivers " );

????StringTokenizer?st? = ? new ?StringTokenizer(driverClasses);

???? while ?(st.hasMoreElements())? {

??????String?driverClassName? = ?st.nextToken().trim();

?????? try ? {

????????Driver?driver? = ?(Driver)

????????????????????????Class.forName(driverClassName).newInstance();

????????DriverManager.registerDriver(driver);

????????drivers.addElement(driver);

????????log( " 成功注冊JDBC驅動程序 " ? + ?driverClassName);

??????}

?????? catch ?(Exception?e)? {

????????log( " 無法注冊JDBC驅動程序:? " ? +

????????????driverClassName? + ? " ,?錯誤:? " ? + ?e);

??????}

????}

??}

?? /**

???*?將文本信息寫入日志文件(溫柔一刀)?

??? */

?? private ? void ?log(String?msg)? {

????log.println( new ?Date()? + ? " :? " ? + ?msg);

??}

?? /**

???*?將文本信息與異常寫入日志文件(溫柔一刀)?

??? */

?? private ? void ?log(Throwable?e,?String?msg)? {

????log.println( new ?Date()? + ? " :? " ? + ?msg);

????e.printStackTrace(log);

??}

?? /**

???*?此內部類定義了一個連接池.它能夠根據要求創建新連接,直到預定的最

???*?大連接數為止.在返回連接給客戶程序之前,它能夠驗證連接的有效性.(溫柔一刀)?

??? */

?? class ?DBConnectionPool? {

???? private ? int ?checkedOut;

???? private ?Vector?freeConnections? = ? new ?Vector();

???? private ? int ?maxConn;

???? private ?String?name;

???? private ?String?password;

???? private ?String?URL;

???? private ?String?user;

???? /**

?????*?創建新的連接池

?????*

?????*? @param ?name?連接池名字

?????*? @param ?URL?數據庫的JDBC?URL

?????*? @param ?user?數據庫帳號,或?null

?????*? @param ?password?密碼,或?null(溫柔一刀)?

?????*? @param ?maxConn?此連接池允許建立的最大連接數

????? */

???? public ?DBConnectionPool(String?name,?String?URL,?String?user,?String?password,

???????????????????????????? int ?maxConn)? {

?????? this .name? = ?name;

?????? this .URL? = ?URL;

?????? this .user? = ?user;

?????? this .password? = ?password;

?????? this .maxConn? = ?maxConn;

????}

???? /**

?????*?將不再使用的連接返回給連接池(溫柔一刀)?

?????*

?????*? @param ?con?客戶程序釋放的連接

????? */

???? public ? synchronized ? void ?freeConnection(Connection?con)? {

// ?將指定連接加入到向量末尾

??????freeConnections.addElement(con);

??????checkedOut -- ;

??????notifyAll();

????}

???? /**

?????*?從連接池獲得一個可用連接.如沒有空閑的連接且當前連接數小于最大連接

?????*?數限制,則創建新連接.如原來登記為可用的連接不再有效,則從向量刪除之,

?????*?然后遞歸調用自己以嘗試新的可用連接.(溫柔一刀)?

????? */

???? public ? synchronized ?Connection?getConnection()? {

??????Connection?con? = ? null ;

?????? if ?(freeConnections.size()? > ? 0 )? {

// ?獲取向量中第一個可用連接

????????con? = ?(Connection)?freeConnections.firstElement();

????????freeConnections.removeElementAt( 0 );

???????? try ? {

?????????? if ?(con.isClosed())? {

????????????log( " 從連接池 " ? + ?name + " 刪除一個無效連接 " );

// ?遞歸調用自己,嘗試再次獲取可用連接

????????????con? = ?getConnection();

??????????}

????????}

???????? catch ?(SQLException?e)? {

??????????log( " 從連接池 " ? + ?name + " 刪除一個無效連接 " );

// ?遞歸調用自己,嘗試再次獲取可用連接

??????????con? = ?getConnection();

????????}

??????}

?????? else ? if ?(maxConn? == ? 0 ? || ?checkedOut? < ?maxConn)? {

????????con? = ?newConnection();

??????}

?????? if ?(con? != ? null )? {

????????checkedOut ++ ;

??????}

?????? return ?con;

????}

???? /**

?????*?從連接池獲取可用連接.可以指定客戶程序能夠等待的最長時間

?????*?參見前一個getConnection()方法.

?????*

?????*? @param ?timeout?以毫秒計的等待時間限制

????? */

???? public ? synchronized ?Connection?getConnection( long ?timeout)? {

?????? long ?startTime? = ? new ?Date().getTime();

??????Connection?con;

?????? while ?((con? = ?getConnection())? == ? null )? {

???????? try ? {

??????????wait(timeout);

????????}

???????? catch ?(InterruptedException?e)? {}

???????? if ?(( new ?Date().getTime()? - ?startTime)? >= ?timeout)? {

// ?wait()返回的原因是超時

?????????? return ? null ;

????????}

??????}

?????? return ?con;

????}

???? /**

?????*?關閉所有連接(溫柔一刀)?

????? */

???? public ? synchronized ? void ?release()? {

??????Enumeration?allConnections? = ?freeConnections.elements();

?????? while ?(allConnections.hasMoreElements())? {

????????Connection?con? = ?(Connection)?allConnections.nextElement();

???????? try ? {

??????????con.close();

??????????log( " 關閉連接池 " ? + ?name + " 中的一個連接 " );

????????}

???????? catch ?(SQLException?e)? {

??????????log(e,? " 無法關閉連接池 " ? + ?name + " 中的連接 " );

????????}

??????}

??????freeConnections.removeAllElements();

????}

???? /**

?????*?創建新的連接(溫柔一刀)?

????? */

???? private ?Connection?newConnection()? {

??????Connection?con? = ? null ;

?????? try ? {

???????? if ?(user? == ? null )? {

??????????con? = ?DriverManager.getConnection(URL);

????????}

???????? else ? {

??????????con? = ?DriverManager.getConnection(URL,?user,?password);

????????}

????????log( " 連接池 " ? + ?name + " 創建一個新的連接 " );

??????}

?????? catch ?(SQLException?e)? {

????????log(e,? " 無法創建下列URL的連接:? " ? + ?URL);

???????? return ? null ;

??????}

?????? return ?con;

????}

??}

}

db.properties文件(溫柔一刀)

drivers=com.mysql.jdbc.Driver

logfile=C:\\StrutsArticle.log

idb.url=jdbc:mysql://localhost/StrutsArticle?useUnicode=true &characterEncoding =gb2312

idb.maxconn=100

idb.user=root

idb.password=

posted on 2006-07-09 04:35 溫柔一刀閱讀(435) 評論(0) 編輯收藏所屬分類: java相關

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