一个连接池的例子（来自JIVE）（1）

一个连接池的例子（来自JIVE）（1）

- 中国WEB开发者网络 (http://www.webasp.net)
-- 技术教程 (http://www.webasp.net/article/)
--- 一个连接池的例子（来自JIVE）（1） (http://www.webasp.net/article/8/7018.htm)

-- 作者：未知
-- 发布日期： 2003-07-26

//文件：DbConnectionDefaultPool.java的第一部分

//请注意看里面注明的一处需要修改连接参数的地方
package com.qingtuo.db.pool;

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

/**
* Default Jive connection provider. It uses the excellent connection pool
* available from http://www.javaexchange.com. This connection provider is a
* a good choice unless you can use a container-managed one.
*/
public class DbConnectionDefaultPool extends DbConnectionProvider {

 private static final String NAME = "Default Connection Pool";
 private static final String DESCRIPTION = "The default connection provider "
 + "that uses the connection pool from javaexchange.com. It works with "
 + "almost any database setup, is customizable, and offers good performance. "
 + "Use this connection provider unless you have your own or can use a "
 + "container managed connection pool.";
 private static final String AUTHOR = "CoolServlets.com";
 private static final int MAJOR_VERSION = 1;
 private static final int MINOR_VERSION = 0;
 private static final boolean POOLED = true;

 private ConnectionPool connectionPool = null;
 private Properties props;
 private Properties propDescriptions;

 private Object initLock = new Object();

 public DbConnectionDefaultPool() {
 //this.manager = manager;
 props = new Properties();
 propDescriptions = new Properties();
 //Initialize all property values
 initializeProperties();
 //Load any existing property values
 loadProperties();
 }

 /**
 * Returns a database connection.
 */
 public Connection getConnection() {
 if (connectionPool == null) {
 //block until the init has been done
 synchronized(initLock) {
 //if still null, something has gone wrong
 if (connectionPool == null) {
 System.err.println("Warning: DbConnectionDefaultPool.getConnection() was " +
 "called when the internal pool has not been initialized.");
 return null;
 }
 }
 }
 return new ConnectionWrapper(connectionPool.getConnection(), connectionPool);
 }

 /**
 * Starts the pool.
 */
 protected void start() {
 //acquire lock so that no connections can be returned.
 synchronized (initLock) {
 //Get properties
 String driver = props.getProperty("driver");
 String server = props.getProperty("server");
 String username = props.getProperty("username");
 String password = props.getProperty("password");
 int minConnections = 0, maxConnections = 0;
 double connectionTimeout = 0.0;
 try {
 minConnections = Integer.parseInt(props.getProperty("minConnections"));
 maxConnections = Integer.parseInt(props.getProperty("maxConnections"));
 connectionTimeout = Double.parseDouble(props.getProperty("connectionTimeout"));
 }
 catch (Exception e) {
 System.err.println("Error: could not parse default pool properties. " +
 "Make sure the values exist and are correct.");
 e.printStackTrace();
 return;
 }
 String logPath = props.getProperty("logPath");

 try {
 connectionPool = new ConnectionPool(driver, server, username, password,
 minConnections, maxConnections, logPath, connectionTimeout);
 }
 catch (IOException ioe) {
 System.err.println("Error starting DbConnectionDefaultPool: " + ioe);
 ioe.printStackTrace();
 }
 }
 }

 /**
 * Restarts the pool to take into account any property changes.
 */
 protected void restart() {
 //Kill off pool.
 destroy();
 //Reload properties.
 loadProperties();
 //Start a new pool.
 start();
 }

 /**
 * Destroys the connection pool.
 */
 protected void destroy() {
 if (connectionPool != null) {
 try {
 connectionPool.destroy(1);
 }
 catch (Exception e) {
 e.printStackTrace();
 }
 }
 //Release reference to connectionPool
 connectionPool = null;
 }

 /**
 * Returns the value of a property of the connection provider.
 *
 * @param name the name of the property.
 * @returns the value of the property.
 */
 public String getProperty(String name) {
 return (String)props.get(name);
 }

 /**
 * Returns the description of a property of the connection provider.
 *
 * @param name the name of the property.
 * @return the description of the property.
 */
 public String getPropertyDescription(String name) {
 return (String)propDescriptions.get(name);
 }

 /**
 * Returns an enumeration of the property names for the connection provider.
 */
 public Enumeration propertyNames() {
 return props.propertyNames();
 }

 /**
 * Sets a property of the connection provider. Each provider has a set number
 * of properties that are determined by the author. Trying to set a non-
 * existant property will result in an IllegalArgumentException.
 *
 * @param name the name of the property to set.
 * @param value the new value for the property.
 *
 */
 public void setProperty(String name, String value) {
 props.put(name, value);
 saveProperties();
 }

 /**
 * Give default values to all the properties and descriptions.
 */
 private void initializeProperties() {
 props.put("driver","");
 props.put("server","");
 props.put("username","");
 props.put("password","");
 props.put("minConnections","");
 props.put("maxConnections","");
 props.put("logPath","");
 props.put("connectionTimeout","");

 propDescriptions.put("driver","JDBC driver. e.g. 'oracle.jdbc.driver.OracleDriver'");
 propDescriptions.put("server","JDBC connect string. e.g. 'jdbc:oracle:thin:@203.92.21.109:1526:orcl'");
 propDescriptions.put("username","Database username. e.g. 'Scott'");
 propDescriptions.put("password","Database password. e.g. 'Tiger'");
 propDescriptions.put("minConnections","Minimum # of connections to start with in pool. Three is the recommended minimum");
 propDescriptions.put("maxConnections","Maximum # of connections in dynamic pool. Fifteen should give good performance for an average load.");
 propDescriptions.put("logPath","Absolute path name for log file. e.g. 'c:\\logs\\jiveDbLog.log'");
 propDescriptions.put("connectionTimeout","Time in days between connection resets. e.g. '.5'");
 }

 /**
 * Load whatever properties that already exist.
 */
 private void loadProperties() {
 //在这里修改一些连接参数
 //in 2000
 /*
 String driver="org.gjt.mm.mysql.Driver";
 String server="jdbc:mysql://192.100.100.11/pcc";
 String username="pcc";
 String password="pcc123";
 String minConnections="3";
 String maxConnections="10";
 String logPath="c:\\temp\\qingtuoDbLog.log";
 String connectionTimeout="0.5";
 */
 //in Linux

 String driver="org.gjt.mm.mysql.Driver";
 String server="jdbc:mysql://192.100.100.1/qingtuo";
 //String server="jdbc:mysql://192.168.0.1/qingtuo";
 String username="qingtuo";
 String password="qingtuo";
 String minConnections="3";
 String maxConnections="20";
 String logPath="c:\\temp\\qingtuoDbLog.log";
// String logPath="/tmp/qingtuoDbLog.log";
 String connectionTimeout="0.5";


 if (driver != null) { props.setProperty("driver", driver); }
 if (server != null) { props.setProperty("server", server); }
 if (username != null) { props.setProperty("username", username); }
 if (password != null) { props.setProperty("password", password); }
 //if (database != null) { props.setProperty("database", database); }
 if (minConnections != null) { props.setProperty("minConnections", minConnections); }
 if (maxConnections != null) { props.setProperty("maxConnections", maxConnections); }
 if (logPath != null) { props.setProperty("logPath", logPath); }
 if (connectionTimeout != null) { props.setProperty("connectionTimeout", connectionTimeout); }
 }

 private void saveProperties() {
 PropertyManager.setProperty("DbConnectionDefaultPool.driver", props.getProperty("driver"));
 PropertyManager.setProperty("DbConnectionDefaultPool.server", props.getProperty("server"));
 PropertyManager.setProperty("DbConnectionDefaultPool.username", props.getProperty("username"));
 PropertyManager.setProperty("DbConnectionDefaultPool.password", props.getProperty("password"));
 PropertyManager.setProperty("DbConnectionDefaultPool.minConnections", props.getProperty("minConnections"));
 PropertyManager.setProperty("DbConnectionDefaultPool.maxConnections", props.getProperty("maxConnections"));
 PropertyManager.setProperty("DbConnectionDefaultPool.logPath", props.getProperty("logPath"));
 PropertyManager.setProperty("DbConnectionDefaultPool.connectionTimeout", props.getProperty("connectionTimeout"));
 }

 private class ConnectionPool implements Runnable {
 private Thread runner;

 private Connection[] connPool;
 private int[] connStatus;

 private long[] connLockTime, connCreateDate;
 private String[] connID;
 private String dbDriver, dbServer, dbLogin, dbPassword, logFileString;
 private int currConnections, connLast, minConns, maxConns, maxConnMSec;

 //available: set to false on destroy, checked by getConnection()
 private boolean available=true;

 private PrintWriter log;
 private SQLWarning currSQLWarning;
 private String pid;

 /**
 * Creates a new Connection Broker 
 * dbDriver: JDBC driver. e.g. 'oracle.jdbc.driver.OracleDriver' 
 * dbServer: JDBC connect string. e.g. 'jdbc:oracle:thin:@203.92.21.109:1526:orcl' 
 * dbLogin: Database login name. e.g. 'Scott' 
 * dbPassword: Database password. e.g. 'Tiger' 
 * minConns: Minimum number of connections to start with. 
 * maxConns: Maximum number of connections in dynamic pool. 
 * logFileString: Absolute path name for log file. e.g. 'c:\temp\mylog.log' 
 * maxConnTime: Time in days between connection resets. (Reset does a basic cleanup) 
 */
 public ConnectionPool (String dbDriver, String dbServer, String dbLogin,
 String dbPassword, int minConns, int maxConns,
 String logFileString, double maxConnTime) throws IOException
 {
 connPool = new Connection[maxConns];
 connStatus = new int[maxConns];
 connLockTime = new long[maxConns];
 connCreateDate = new long[maxConns];
 connID = new String[maxConns];
 currConnections = minConns;
 this.maxConns = maxConns;
 this.dbDriver = dbDriver;
 this.dbServer = dbServer;
 this.dbLogin = dbLogin;
 this.dbPassword = dbPassword;
 this.logFileString = logFileString;
 maxConnMSec = (int)(maxConnTime * 86400000.0); //86400 sec/day
 if(maxConnMSec < 30000) { // Recycle no less than 30 seconds.
 maxConnMSec = 30000;
 }

 try {
 log = new PrintWriter(new FileOutputStream(logFileString),true);

 // Can't open the requested file. Open the default file.
 }
 catch (IOException e1) {
 System.err.println("Warning: DbConnectionDefaultPool could not open \""
 + logFileString + "\" to write log to. Make sure that your Java " +
 "process has permission to write to the file and that the directory exists."
 );
 try {
 log = new PrintWriter(new FileOutputStream("DCB_" +
 System.currentTimeMillis() + ".log"), true
 );
 }
 catch (IOException e2) {
 throw new IOException("Can't open any log file");
 }
 }

 // Write the pid file (used to clean up dead/broken connection)
 SimpleDateFormat formatter
 = new SimpleDateFormat ("yyyy.MM.dd G 'at' hh:mm:ss a zzz");
 java.util.Date nowc = new java.util.Date();
 pid = formatter.format(nowc);

 BufferedWriter pidout = new BufferedWriter(new
 FileWriter(logFileString + "pid"));
 pidout.write(pid);
 pidout.close();

 log.println("Starting ConnectionPool:");
 log.println("dbDriver = " + dbDriver);
 log.println("dbServer = " + dbServer);
 log.println("dbLogin = " + dbLogin);
 log.println("log file = " + logFileString);
 log.println("minconnections = " + minConns);
 log.println("maxconnections = " + maxConns);
 log.println("Total refresh interval = " + maxConnTime + " days");
 log.println("-----------------------------------------");


 // Initialize the pool of connections with the mininum connections:
 // Problems creating connections may be caused during reboot when the
 // servlet is started before the database is ready. Handle this
 // by waiting and trying again. The loop allows 5 minutes for
 // db reboot.
 boolean connectionsSucceeded=false;
 int dbLoop=20;

 try {
 for(int i=1; i < dbLoop; i++) {
 try {
 for(int j=0; j < currConnections; j++) {
 log.println("Create Conn "+j);
 createConn(j);
 }
 connectionsSucceeded=true;
 break;
 }
 catch (SQLException e){
 log.println("--->Attempt (" + String.valueOf(i) +
 " of " + String.valueOf(dbLoop) +
 ") failed to create new connections set at startup: ");
 log.println(" " + e);
 log.println(" Will try again in 15 seconds...");
 try { Thread.sleep(15000); }
 catch(InterruptedException e1) {}
 }
 }
 if(!connectionsSucceeded) { // All attempts at connecting to db exhausted
 log.println("\r\nAll attempts at connecting to Database exhausted");
 throw new IOException();
 }
 }
 catch (Exception e) {
 throw new IOException();
 }

 // Fire up the background housekeeping thread

 runner = new Thread(this);
 runner.start();

 } //End ConnectionPool()

webasp.net