dbconnection.java

jsp 应用开发技术光盘 是《jsp应用开发技术》这本书的源代码

package ch13;

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

/** 
 *
 * 通过配置connection.txt文件
 * 可以获得到各种数据库的连接
 */
public final class DBConnection {
	private static String driver;
	private static String serverURL;
	private static String username;
	private static String password;
	private static Connection conn = null;
	private static String connectionFileName = "src/ch13/connection.txt";
		
	private static Object initLock = new Object();
	
	private DBConnection() { }
	
	public static Connection getConnection() {
		if (conn == null) {
			synchronized(initLock) {
				loadProperties();
				try {
					Class.forName(driver);
				}
				catch (ClassNotFoundException e) {
					System.out.println(e.toString());
				}
				try {
					conn = DriverManager.getConnection(serverURL, username, password);			
				}
				catch (SQLException e) {
					System.out.println(e.toString());
				}
			}	
		}
		
		return conn;
	}
	
	private static void loadProperties() {	
		Properties connectionAdmin = new Properties();
		
		System.out.println("连接配置文件：" + connectionFileName);
		
		// 从配置文件中加载参数
		try{			
			connectionAdmin.load(new FileInputStream(connectionFileName));
		}
		catch(IOException e){
			System.out.println("找不到文件：" + connectionFileName);
			System.out.println(e.toString());
		}
		
		// 设置数据库连接参数
		driver    = (String)connectionAdmin.get("driver");
		serverURL = (String)connectionAdmin.get("serverURL");
		username  = (String)connectionAdmin.get("username");
		password  = (String)connectionAdmin.get("password");
	}
	
	// Test methods.
	public static void main(String[] args) {
		System.out.println("开始连接数据库...");
		Connection conn = getConnection();
		System.out.println("-------------------------------");
		System.out.println("   driver: " + driver);
		System.out.println("serverURL: " + serverURL);
		System.out.println(" username: " + username);
		System.out.println(" password: " + password);
		System.out.println("-------------------------------");
		if (conn != null) System.out.println("连接数据库成功！");
	}
	
}