dbconnectionmanager.java

一个数据库连接池的完整代码

package eise.db;
//------------------------------------------------------------------------------
import java.io.*;
import java.sql.*;
import java.util.*;
//------------------------------------------------------------------------------
public class DBConnectionManager{

  private static DBConnectionManager instance;
  private static int clients;//使用此连接池的DbConnect的数目
  private Vector drivers;//驱动程序列表
  private PrintWriter log;//日志文件
  private Hashtable pools;//连接池
//------------------------------------------------------------------------------
    private DBConnectionManager(){
        drivers = new Vector();
        pools = new Hashtable();
        init();
    }
//------------------------------------------------------------------------------
    private void init(){
        java.io.InputStream inputstream = getClass().getResourceAsStream("db_pool.properties");
        Properties properties = new Properties();
        try{properties.load(inputstream);}
        catch(Exception ee)
           {System.err.println("加载db.properties文件时出错："+ee.toString());
            return;
           }
        String log_file_name= properties.getProperty("logfile", "DBConnectionManager.log");
        try{log = new PrintWriter(new FileWriter(log_file_name, true), true);}
        catch(IOException ee)
           {System.err.println("打开LOG文件时出错: " + log_file_name);
            log = new PrintWriter(System.err);
           }
        loadDrivers(properties);
        createPools(properties);
    }
//------------------------------------------------------------------------------
    private void loadDrivers(Properties properties){
        String driver_items = properties.getProperty("drivers");
        for(StringTokenizer stringtokenizer = new StringTokenizer(driver_items); stringtokenizer.hasMoreElements();)
           {String driver_item = stringtokenizer.nextToken().trim();
            try{Driver driver = (Driver)Class.forName(driver_item).newInstance();
                DriverManager.registerDriver(driver);
                drivers.addElement(driver);
                log("成功加载数据库驱动程序：" + driver_item);
               }
            catch(Exception ee)
               {log("加载数据库驱动程序时出错: " + driver_item + "；错误信息是: " + ee.toString());
               }
          }
    }
//------------------------------------------------------------------------------
    private void createPools(Properties properties){
        for(Enumeration enumeration = properties.propertyNames(); enumeration.hasMoreElements();)
           {String db_url_name=(String)enumeration.nextElement();
            if(db_url_name.endsWith(".url"))
              {String db_name = db_url_name.substring(0, db_url_name.lastIndexOf("."));
               String db_url = properties.getProperty(db_name + ".url");
               if(db_url == null)
                 {log("加载数据库项目时出错：" + db_name);
                 }
               else
                 {String db_user = properties.getProperty(db_name + ".user");
                  String db_password = properties.getProperty(db_name + ".password");
                  String db_max = properties.getProperty(db_name + ".maxconn", "0");
                  int max_int;
                  try{max_int = Integer.valueOf(db_max).intValue();}
                  catch(NumberFormatException _ex)
                     {log("最大连接数目的参数有误: " + db_max + "所属数据库类型为: " + db_name);
                      max_int = 0;
                     }
                  DBConnectionPool dbconnectionpool = new DBConnectionPool(this,db_name, db_url, db_user, db_password, max_int);
                  pools.put(db_name, dbconnectionpool);
                  log("成功创建数据库连接池，数据库的类型为：" + db_name);
                 }
              }
        }
    }
//------------------------------------------------------------------------------
    public void freeConnection(String db_name, Connection connection){
        DBConnectionPool dbconnectionpool = (DBConnectionPool)pools.get(db_name);
        if(dbconnectionpool != null){dbconnectionpool.freeConnection(connection);}
    }
//------------------------------------------------------------------------------
    public Connection getConnection(String db_name){
        DBConnectionPool dbconnectionpool = (DBConnectionPool)pools.get(db_name);
        if(dbconnectionpool != null){return dbconnectionpool.getConnection();}
        else{return null;}
    }
//------------------------------------------------------------------------------
    public Connection getConnection(String db_name, long limit_long){
        DBConnectionPool dbconnectionpool = (DBConnectionPool)pools.get(db_name);
        if(dbconnectionpool != null){return dbconnectionpool.getConnection(limit_long);}
        else{return null;}
    }
//------------------------------------------------------------------------------
    public static synchronized DBConnectionManager getInstance(){
        if(instance == null){instance = new DBConnectionManager();}
        clients++;
        return instance;
    }
//------------------------------------------------------------------------------
    public void log(String messageStr){
        log.println("日志记录：时间－　"+String.valueOf(new java.util.Date()) + "　内容: " + messageStr);
    }
//------------------------------------------------------------------------------
    public void log(Throwable throwable, String messageStr){
        log.println("日志记录：时间－　"+String.valueOf(new java.util.Date()) + "　内容: " + messageStr);
        throwable.printStackTrace(log);
    }
//------------------------------------------------------------------------------
    public synchronized void release(){
        if(--clients != 0){return;}
        DBConnectionPool dbconnectionpool;
        for(Enumeration enumeration = pools.elements(); enumeration.hasMoreElements(); dbconnectionpool.release())
           {dbconnectionpool = (DBConnectionPool)enumeration.nextElement();
           }
        for(Enumeration enumeration1 = drivers.elements(); enumeration1.hasMoreElements();)
           {Driver driver = (Driver)enumeration1.nextElement();
            try{DriverManager.deregisterDriver(driver);
                log("成功注销数据库驱动：" + driver.getClass().getName());
               }
            catch(SQLException ee)
               {log(ee, "注销数据库驱动时出错: " + driver.getClass().getName());
               }
           }
    }
//------------------------------------------------------------------------------
}//end of class
//------------------------------------------------------------------------------