java jdbc连接工具类DBConnectionManager

/**
 * 管理类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 DBConnectionManager {
	
	static private DBConnectionManager instance;
	static private int clients;
	private Vector drivers = new Vector();
	private PrintWriter log;
	private Hashtable pools = new Hashtable();

	/**
	 * 返回唯一实例.如果是第一次调用此方法,则创建实例
	 * @return DBConnectionManager 唯一实例
	 */
	static synchronized public DBConnectionManager getInstance() {
		if (instance == null) {
			instance = new DBConnectionManager();
		}
		clients++;
		return instance;
	}
	/**
	 * 建构函数私有以防止其它对象创建本类实例
	 */
	private DBConnectionManager() {
		init();
	}
	/**
	 * 读取属性完成初始化
	 */
	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", "dbconMgr.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);
	}
	/**
	 * 装载和注册所有JDBC驱动程序
	 * @param 参数  :  db.properties
	 */
	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("成功注册JDBC驱动程序" + driverClassName);
			} catch (Exception e) {
				e.printStackTrace();
				log("无法注册JDBC驱动程序: " + driverClassName + ", 错误: " + e);
			}
		}
	}

由AXIN编辑于2014-2-12 16:36:05