功能完善的Java连接池调用实例

2019-11-18 15:05:59

字体：大中小

来源：转载

供稿：网友

　　/**
* Title: ConnectPool.java
* Description: 连接池治理器
* Copyright: Copyright (c) 2002/12/25
* Company:
* Author :
* Version 2.0
*/

import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;

/**
* 治理类DBConnectionManager支持对一个或多个由属性文件定义的数据库连接
* 池的访问.客户程序可以调用getInstance()方法访问本类的唯一实例.
*/
public class ConnectPool
{
static public ConnectPool instance; // 唯一实例
static public int clients;
public Vector drivers = new Vector(); //驱动
public PRintWriter log;
public Hashtable pools = new Hashtable(); //连接

/**
* 返回唯一实例.假如是第一次调用此方法,则创建实例
*
* @return DBConnectionManager 唯一实例
*/
static synchronized public ConnectPool getInstance()
{
if (instance == null)
{
instance = new ConnectPool();
}

clients++;

return instance;
}

/**
* 建构函数私有以防止其它对象创建本类实例
*/
public ConnectPool() {
init();
}

/**
* 将连接对象返回给由名字指定的连接池
*
* @param name 在属性文件中定义的连接池名字
* @param con 连接对象
*/
public void freeConnection(String name, Connection con)
{
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null)
{
pool.freeConnection(con);
}
else
{
System.out.println("pool ==null");
}
clients--;
}

/**
* 获得一个可用的(空闲的)连接.假如没有可用连接,且已有连接数小于最大连接数
* 限制,则创建并返回新连接
*
* @param name 在属性文件中定义的连接池名字
* @return Connection 可用连接或null
*/
public Connection getConnection(String name)
{
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null)
{
//return pool.getConnection();
return pool.returnConnection();
}
return null;
}

/**
* 获得一个可用连接.若没有可用连接,且已有连接数小于最大连接数限制,
* 则创建并返回新连接.否则,在指定的时间内等待其它线程释放连接.
*
* @param name 连接池名字
* @param time 以毫秒计的等待时间
* @return Connection 可用连接或null
*/
public Connection getConnection(String name, long time)
{
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null)
{
return pool.getConnection(time);
}
return null;
}

/**
* 关闭所有连接,撤销驱动程序的注册
*/
public synchronized void release()
{
// 等待直到最后一个客户程序调用
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("撤销JDBC驱动程序 " + driver.getClass().getName()+"的注册");
}
catch (SQLException e)
{
log(e, "无法撤销下列JDBC驱动程序的注册: " + driver.getClass().getName());
}
}
}

/**
* 根据指定属性创建连接池实例.
*
* @param props 连接池属性
*/
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("没有为连接池" + 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("错误的最大连接数限制: " + maxconn + " .连接池: " + poolName);
max = 0;
}
DBConnectionPool pool = new DBConnectionPool(poolName, url, user, password, max);
pools.put(poolName, pool);
log("成功创建连接池" + poolName);
}
}
}

/**
* 读取属性完成初始化
*/
private void init()
{
try
{
Properties p = new Properties();
String configs = System.getProperty("user.dir")+"/conf/db.properties";

System.out.println("configs file local at "+configs);
FileInputStream is = new FileInputStream(configs);
Properties dbProps = new Properties();
try
{
dbProps.load(is);
}
catch (Exception e)
{
System.err.println("不能读取属性文件. " +"请确保db.properties在CLASSPATH指定的路径中");
return;
}
String logFile = dbProps.getProperty("logfile", "DBConnectionManager.log");
try{

log = new PrintWriter(new FileWriter(logFile, true), true);
}
catch (IOException e)
{
System.err.println("无法打开日志文件: " + logFile);
log = new PrintWriter(System.err);
}
loadDrivers(dbProps);
createPools(dbProps); }catch(Exception e){}
}

/**
171 * 装载和注册所有JDBC驱动程序
172 *
173 * @param props 属性
174 */
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);
System.out.println(driverClassName);
log("成功注册JDBC驱动程序" + driverClassName);
}
catch (Exception e)
{
log("无法注册JDBC驱动程序: " +
driverClassName + ", 错误: " + e);
}
}
}

/**
* 将文本信息写入日志文件
*/
private void log(String msg)
{
log.println(new Date() + ": " + msg);
}

/**
* 将文本信息与异常写入日志文件
*/
private void log(Throwable e, String msg)
{
log.println(new Date() + ": " + msg);
e.printStackTrace(log);
}

/**
* 此内部类定义了一个连接池.它能够根据要求创建新连接,直到预定的最
* 大连接数为止.在返回连接给客户程序之前,它能够验证连接的有效性.
*/

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;

/**
* 创建新的连接池
*
* @param name 连接池名字
* @param URL 数据库的JDBC URL
* @param user 数据库帐号,或 null
* @param password 密码,或 null
* @param maxConn 此连接池答应建立的最大连接数
*/
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;
}
/**
* 将不再使用的连接返回给连接池
*
* @param con 客户程序释放的连接
*/
public synchronized void freeConnection(Connection con) {
// 将指定连接加入到向量末尾
try
{
if(con.isClosed()){System.out.println("before freeConnection con is closed");}
freeConnections.addElement(con);
Connection contest = (Connection) freeConnections.lastElement();
if(contest.isClosed()){System.out.println("after freeConnection contest is closed");}
notifyAll();
}catch(SQLException e){System.out.println(e);}
}

/**
* 从连接池获得一个可用连接.如没有空闲的连接且当前连接数小于最大连接
* 数限制,则创建新连接.如原来登记为可用的连接不再有效,则从向量删除之,
* 然后递归调用自己以尝试新的可用连接.
*/
public synchronized Connection getConnection()
{
Connection con = null;
if (freeConnections.size() > 0)
{
// 获取向量中第一个可用连接
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed())
{
log("从连接池" + name+"删除一个无效连接");
System.out.println("从连接池" + name+"删除一个无效连接");
// 递归调用自己,尝试再次获取可用连接
con = getConnection();
}
}
catch (SQLException e)
{
log("从连接池" + name+"删除一个无效连接时错误");
System.out.println("从连接池" + name+"删除一个无效连接出错");
// 递归调用自己,尝试再次获取可用连接
con = getConnection();
}
if(freeConnections.size()>maxConn)
{ System.out.println(" 删除一个溢出连接 ");
releaSEOne();
}
}

else if((maxConn == 0)(freeConnections.size()<maxConn))
{
con = newConnection();
}

return con;
}

public synchronized Connection returnConnection()
{
Connection con = null;
//假如闲置小于最大连接,返回一个新连接
if(freeConnections.size()<maxConn)
{
con = newConnection();
}
//假如闲置大于最大连接，返回一个可用的旧连接
else if(freeConnections.size()>=maxConn)
{

con = (Connection) freeConnections.firstElement();
System.out.println(" [a 连接池可用连接数 ] : "+"[ "+freeConnections.size()+" ]");
freeConnections.removeElementAt(0);
System.out.println(" [b 连接池可用连接数 ] : "+"[ "+freeConnections.size()+" ]");
try
{
if (con.isClosed())
{
log("从连接池" + name+"删除一个无效连接");
System.out.println("从连接池" + name+"删除一个无效连接");
returnConnection();
}
}catch (SQLException e)
{
log("从连接池" + name+"删除一个无效连接时错误");
System.out.println("从连接池" + name+"删除一个无效连接出错");
returnConnection();
}
}
return con;
}

/**
* 从连接池获取可用连接.可以指定客户程序能够等待的最长时间
* 参见前一个getConnection()方法.
*
* @param timeout 以毫秒计的等待时间限制
*/
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()返回的原因是超时
return null;
}
}
return con;
}

/**
* 关闭所有连接
*/
public synchronized void release()
{
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements())
{
Connection con = (Connection) allConnections.nextElement();
try {
con.close();
log("关闭连接池" + name+"中的一个连接");
}
catch (SQLException e)
{
log(e, "无法关闭连接池" + name+"中的连接");
}
}
freeConnections.removeAllElements();
}
/**
* 关闭一个连接
*/
public synchronized void releaseOne()
{
if(freeConnections.firstElement()!=null)
{ Connection con = (Connection) freeConnections.firstElement();
try {
con.close();
System.out.println("关闭连接池" + name+"中的一个连接");
log("关闭连接池" + name+"中的一个连接");
}
catch (SQLException e)
{

System.out.println("无法关闭连接池" + name+"中的一个连接");
log(e, "无法关闭连接池" + name+"中的连接");
}
}
else
{
System.out.println("releaseOne() bug.......................................................");

}
}

/**
* 创建新的连接
*/
private Connection newConnection()
{
Connection con = null;
try
{
if (user == null) {
con = DriverManager.getConnection(URL);
}
else{
con = DriverManager.getConnection(URL, user, password);
}
log("连接池" + name+"创建一个新的连接");

}
catch (SQLException e) {
log(e, "无法创建下列URL的连接: " + URL);
return null;
}
return con;
}
}
}

================================
/**
* Title: ConnectPool.java
* Description: 数据库操作
* Copyright: Copyright (c) 2002/12/25
* Company:
* Author :
* remark : 加入指针回滚
* Version 2.0
*/

import java.io.*;
import com.sjky.pool.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
import java.net.*;

public class PoolMan extends ConnectPool {

private ConnectPool connMgr;
private Statement stmt;
private Connection con ;
private ResultSet rst;

/**
*对象连接初始化
* */

public Connection getPool(String name) throws Exception
{
try{
connMgr = ConnectPool.getInstance();
con = connMgr.getConnection(name);
}catch(Exception e)
{
System.err.println("不能创建连接!请尝试重启应用服务器");

}
return con;
}

/**
*同以上方法,加入连接空闲等待时间
*待用方法
* */

public Connection getPool_t(String name, long time) throws Exception
{
try{
connMgr = ConnectPool.getInstance();
con = connMgr.getConnection(name,time);
}catch(Exception e)
{
System.err.println("不能创建连接!");

}
return con;
}
/**
*执行查询方法1
* */
public ResultSet executeQuery(String SqlStr) throws Exception
{
ResultSet result = null;
try
{
stmt = con.createStatement();
result = stmt.executeQuery(SqlStr);
// here add one line by jnma 12.11
con.commit();
}
catch(java.sql.SQLException e)
{
throw new Exception("执行查询语句出错");
}
return result;
}
/**
*执行查询方法2
* */
public ResultSet getRst(String SqlStr) throws Exception
{
// ResultSet result = null;
try
{
stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
rst = stmt.executeQuery(SqlStr);
// here add one line by jnma 12.11
con.commit();
}
catch(java.sql.SQLException e)
{
throw new Exception("执行查询语句出错");
}
return rst;
}
/**
*执行更新
* */
public int Update(String SqlStr) throws Exception
{
int result = -1;
try
{
stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
result = stmt.executeUpdate(SqlStr);
// here add one line by jnma 12.11
con.commit();
if(result==0)
System.out.println("执行delete,update,insert SQL出错");
}
catch(java.sql.SQLException e)
{
System.err.println("执行delete,update,insert SQL出错");
}
return result;
}

/**
*执行事务处理
* */
public boolean handleTransaction(Vector SqlArray) throws Exception
{
boolean result = false;
int ArraySize = SqlArray.size();
try
{
stmt = con.createStatement();
con.setAutoCommit(false);
System.out.println("ArraySize is" +ArraySize);
for(int i=0;i<ArraySize;i++)
{
System.out.println(" 开始执行语句"+(String)SqlArray.elementAt(i));
stmt.executeUpdate((String)SqlArray.elementAt(i));
System.out.println(" 执行成功");
}
con.commit();
con.setAutoCommit(true) ;//必须
System.out.println("事务执行成功");
result = true;
}
catch(java.sql.SQLException e)
{
try
{
System.out.println(e.toString());
System.out.println("数据库操作失败");
con.rollback();
}
catch(java.sql.SQLException Te)
{
System.err.println("事务出错回滚异常");
}
}
try
{
con.setAutoCommit(true);
}
catch(java.sql.SQLException e)
{
System.err.println("设置自动提交失败");
}
return result;
}

/**
*释放连接
* */
public void close(String name) throws Exception
{
try
{
if(stmt!=null)
stmt.close();
if(con!=null)
{
connMgr.freeConnection(name,con);

System.out.println(" [c 正在释放一个连接 ] ");

}
}
catch(java.sql.SQLException e)
{
System.err.println("释放连接出错");
}
}

}
===========================
属性文件db.properties放在conf下

#drivers=com.inet.tds.TdsDriver
#logfile=c:/resin-2.1.4/DBConnectPool-log.txt
#test.maxconn=1000
#test.url=jdbc:inetdae:SERVER:1433?sql7=true
#test.user=sa
#test.password=test

drivers=com.microsoft.jdbc.sqlserver.SQLServerDriver
logfile=F:/resin-2.1.4/DBConnectPool-log.txt
test.maxconn=20
test.url=jdbc:microsoft:sqlserver://192.168.0.5:1433;DatabaseName=test
test.user=sa
test.password=test

#drivers=Oracle.jdbc.driver.OracleDriver
#logfile=c:/resin-2.1.4/DBConnectPool-log.txt
#test.maxconn=100
#test.url=jdbc:oracle:thin:@192.168.0.10:1521:myhome
#test.user=system
#test.password=manager
#MySQL端3306

#drivers=org.gjt.mm.mysql.Driver
#logfile=c:/resin-2.1.4/DBConnectPool-log.txt
#test.maxconn=100
#test.url=jdbc:mysql://192.168.0.4:3306/my_test
#test.user=root
#test.password=system

上一篇：非官方观点 Java vs .NET

下一篇：构造函数的继承问题