dbconnection.java

一个可以存储和打印成绩单的系统

package org.minjey.cjsjk.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

import org.minjey.cjsjk.util.PropertyDict;
import org.minjey.cjsjk.util.PropertyLoader;

public class DBConnection {
	
	private static Connection conn = null;
	
	public static Connection getConnection() {
		if(conn == null) {
			Properties properties = PropertyLoader.loadSystemProperty();
			conn = new DBConnection().getConnection(properties);
			try {
				conn.setAutoCommit(false);
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		return conn;
	}
	
	public static void closeConnecion() {
		if(conn != null) {
			try {
				boolean closed = conn.isClosed();
				if(!closed) {
					conn.close();
				}
			} catch (SQLException e) {
				e.printStackTrace();
			}
			conn = null;
		}
	}

	private Connection getConnection(Properties properties) {
		Connection conn = null;

		String driver = properties.getProperty(PropertyDict.DBDRIVER);
		String protocol = properties.getProperty(PropertyDict.DBPROTOCOL);
		String dbname = properties.getProperty(PropertyDict.DBDBNAME);
		String username = properties.getProperty(PropertyDict.DBUSERNAME);
		String password = properties.getProperty(PropertyDict.DBPASSWORD);

		Properties props = new Properties();
		props.put("user", username);
		props.put("password", password);
		System.out.println("Attempt To Connect To Database: " + dbname
				+ ".");
		try {
			Class.forName(driver).newInstance();
			conn = DriverManager.getConnection(protocol + dbname, props);

			System.out.println("Connect to Database: " + dbname
					+ " Successd.");
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			System.err.println(e);
			String message = "Database '" + dbname + "' not found.";
			String message2 = "数据库“" + dbname + "”未找到。";
			if (message.equals(e.getMessage()) || message2.equals(e.getMessage())) {
				DBCreater dc = new DBCreater();
				dc.createNewDB(driver, protocol, dbname, username,
						password);
				dc.prepareDefaultData();
				conn = new DBConnection().getConnection(properties);
			} else {
				e.printStackTrace();
			}
			System.out.println();
		}
		return conn;
	}

	public static void main(String[] args) {
		DBConnection.getConnection();
	}
}