databasetool.java

一个非常简单的mvc留言板MVC框架是STRUTS框架的基础

package com.aptech.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

/**
 * 数据库辅助类,单例模式
 * 
 * @author Administrator
 * 
 */
public class DatabaseTool {
	private static Connection conn;

	private static Statement stmt;

	private static final DatabaseTool dt = new DatabaseTool();

	/**
	 * 构造方法私有化,防止被外部实例化
	 * 
	 */
	private DatabaseTool() {
	}

	/**
	 * 得到对象
	 * 
	 * @return
	 */
	public static DatabaseTool getInstance() {
		return dt;
	}

	/**
	 * 创建连接对象
	 * 
	 */
	public void createConnection() {
		try {
			Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
			conn = DriverManager
					.getConnection(
							"jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=t59",
							"sa", "sa");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

	/**
	 *	关闭连接 
	 *
	 */
	public void closeConnection() {
		try {
			if (stmt != null) {
				stmt.close();
				stmt = null;
			}
			if (conn != null) {
				conn.close();
				conn = null;
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	/**
	 * 执行添加,删除,修改SQL语句
	 * @param sql 
	 * @return 如果操作成功,返回真,否则返回假
	 */
	public boolean insertOrUpdateOrDelete(String sql){
		System.out.println(sql);
		if(conn == null){
			this.createConnection();
		}
		try {
			stmt = conn.createStatement();
			stmt.executeUpdate(sql);
			return true;
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return false;
		} finally{
			this.closeConnection();//关闭连接,释放资源
		}
	}
	
	/**
	 * 执行查询语句
	 * @param sql
	 * @return 如果没得到结果,返回空值
	 */
	public ResultSet select(String sql){
		System.out.println(sql);
		if(conn == null){
			this.createConnection();
		}
		try {
			stmt = conn.createStatement();
			ResultSet rs = stmt.executeQuery(sql);
			return rs;
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
	}
}