java中jdbc连接 数据库代码

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBConnection {
    public Connection conn = null; // 声明Connection对象的实例
    public Statement stmt = null; // 声明Statement对象的实例
    public ResultSet rs = null; // 声明ResultSet对象的实例
    //定义保存数据库驱动的变量
    private static String dbClassName = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
    private static String dbUrl = "jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=DB_ATM";
    private static String dbUser = "sa";
    private static String dbPwd = "sa";
    public JDBConnection(String propertyFileName) {// 带属性文件名的构造方法
        Properties prop = new Properties();// 属性集合对象
        InputStream is = null;
        try {
            is = JDBConnection.class.getClassLoader().getResourceAsStream(
                    propertyFileName);// 属性文件输入流
            // is = new FileInputStream("src/" + propertyFileName);
            prop.load(is);// 将属性文件流装载到Properties对象中
            is.close();// 关闭流
            dbClassName = prop.getProperty("dbClassName");
            dbUrl = prop.getProperty("dbUrl");
            dbUser = prop.getProperty("dbUser");
            dbPwd = prop.getProperty("dbPwd");
        } catch (Exception e) {
            System.out.println("属性文件  " + propertyFileName + " 打开失败！");
        }
        try {
            Class.forName(dbClassName);// 1.注册驱动
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    public JDBConnection() {// 默认的不带参数的构造函数
        try {
            Class.forName(dbClassName);// 1.注册驱动
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    public static Connection getConnection() {
        Connection conn = null;
        try {
            // Class.forName(dbClassName);// 1.注册驱动
            //2.建立与数据库的链接
            conn = DriverManager.getConnection(dbUrl, dbUser, dbPwd);
        } catch (Exception ee) {
            ee.printStackTrace();
        }
        if (conn == null) {
         System.err.println("警告: DbConnectionManager.getConnection() 获得数据库链接失败.
         ＼r＼n＼r＼n链接类型:"
                            + dbClassName
                            + "＼r＼n链接位置:"
                            + dbUrl
                            + "＼r＼n用户/密码"
                            + dbUser + "/" + dbPwd);
        }
        return conn;
    }
    /*
     * 功能：执行查询语句
     */
    public ResultSet executeQuery(String sql) {
        try { // 捕捉异常
        // 调用getConnection()方法构造Connection对象的一个实例conn
            conn = getConnection(); 
            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,//3.创建语句
                    ResultSet.CONCUR_READ_ONLY);
            rs = stmt.executeQuery(sql);//4.执行查询
        } catch (SQLException ex) {
            System.err.println(ex.getMessage()); // 输出异常信息
        }
        return rs; // 返回结果集对象 5.结果处理
    }
    /*
     * 功能:执行更新操作
     */
    public int executeUpdate(String sql) {
        int result = 0; // 定义保存返回值的变量
        try { // 捕捉异常
                 // 调用getConnection()方法构造Connection对象的一个实例conn
            conn = getConnection();
            stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                    ResultSet.CONCUR_READ_ONLY);
            result = stmt.executeUpdate(sql); // 执行更新操作
        } catch (SQLException ex) {
            result = 0; // 将保存返回值的变量赋值为0
        }
        return result; // 返回保存返回值的变量
    }
    /*
     * 功能:关闭数据库的连接
     */
    public void close() {//6.释放资源
        try { // 捕捉异常
            try {
                if (rs != null) { // 当ResultSet对象的实例rs不为空时
                    rs.close(); // 关闭ResultSet对象
                }
            } finally {
                try {
                    if (stmt != null) { // 当Statement对象的实例stmt不为空时
                        stmt.close(); // 关闭Statement对象
                    }
                } finally {
                    if (conn != null) { // 当Connection对象的实例conn不为空时
                        conn.close(); // 关闭Connection对象
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace(System.err); // 输出异常信息
        }
    }
}