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package DBHelper;

import java.io.Console;
import java.sql.*;
import java.util.Enumeration;
//import java.util.logging.*;
//import javax.swing.table.*;

/**
 *  SQL 基本操作
 * 通过它,可以很轻松的使用 JDBC 来操纵数据库
 * @author Null
 */
public class DBHelper
{

    /**
     * 驱动
     */
    //public static String driver = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
    public static String driver = "com.mysql.jdbc.Driver";
    /**
     * 连接字符串
     */
    //public static String url = "jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=st";
    public static String url = "jdbc:mysql://127.0.0.1:3306/test";
    /**
     * 用户名
     */
    public static String user = "root";
    /**
     * 密码
     */
    public static String password = "root";

    /**
     * 不允许实例化该类
     */
    private DBHelper()
    {
    }

    /**
     * 获取一个数据库连接
     * 通过设置类的  driver / url / user / password 这四个静态变量来 设置数据库连接属性
     * @return 数据库连接
     */
    public static Connection getConnection()
    {
        try
        {
            //获取驱动
            Class.forName(driver);
        } catch (ClassNotFoundException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
        }

        try
        {
            return DriverManager.getConnection(url, user, password);
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            return null;
        }
    }

    /**
     * 获取一个 Statement
     * 该 Statement 已经设置数据集 可以滚动,可以更新
     * @return 如果获取失败将返回 null,调用时记得检查返回值
     */
    public static Statement getStatement()
    {
        Connection conn = getConnection();
        if (conn == null)
        {
            return null;
        }
        try
        {
            return conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
                    ResultSet.CONCUR_UPDATABLE);
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        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            close(conn);
        }
        return null;
    }

    /**
     * 获取一个 Statement
     * 该 Statement 已经设置数据集 可以滚动,可以更新
     * @param conn 数据库连接
     * @return 如果获取失败将返回 null,调用时记得检查返回值
     */
    public static Statement getStatement(Connection conn)
    {
        if (conn == null)
        {
            return null;
        }
        try
        {

            return conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
            // 设置数据集可以滚动,可以更新
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            return null;
        }
    }

    /**
     * 获取一个带参数的 PreparedStatement
     * 该 PreparedStatement 已经设置数据集 可以滚动,可以更新
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return 如果获取失败将返回 null,调用时记得检查返回值
     */
    public static PreparedStatement getPreparedStatement(String cmdText, Object[] cmdParams)
    {
        Connection conn = getConnection();
        if (conn == null)
        {
            return null;
        }

        PreparedStatement pstmt = null;
        try
        {
            
            pstmt = conn.prepareStatement(cmdText, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
            int i = 1;
            for (Object item : cmdParams) //java foreach遍历集合,要求集合类实现Enumeration接口
            {
                pstmt.setObject(i, item);
                i++;
            }
        } catch (SQLException e)
        {
            e.printStackTrace();
            close(conn);
        }
        return pstmt;
    }

    /**
     *  获取一个带参数的 PreparedStatement
     * 该 PreparedStatement 已经设置数据集 可以滚动,可以更新
     * @param conn 数据库连接
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return 如果获取失败将返回 null,调用时记得检查返回值
     */
    public static PreparedStatement getPreparedStatement(Connection conn, String cmdText, Object[] cmdParams)
    {
        if (conn == null)
        {
            return null;
        }

        PreparedStatement pstmt = null;
        try
        {
            pstmt = conn.prepareStatement(cmdText, ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
            int i = 1;
            for (Object item : cmdParams)
            {
                pstmt.setObject(i, item);
                i++;
            }
        } catch (SQLException ex)
        {
            System.out.println(ex.getMessage());
            //ex.printStackTrace();
            close(pstmt);
        }
        return pstmt;
    }

    /**
     * 执行 SQL 语句,返回结果为整型
     * 主要用于执行非查询语句
     * @param cmdText SQL 语句
     * @return 非负数:正常执行; -1:执行错误; -2:连接错误
     */
    public static int ExecSql(String cmdText)
    {
        Statement stmt = getStatement();
        if (stmt == null)
        {
            return -2;
        }
        int i;
        try
        {
            i = stmt.executeUpdate(cmdText);
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null,ex);
            System.out.println(ex.getMessage());
            i = -1;
        }
        closeConnection(stmt);
        return i;
    }

    /**
     * 执行 SQL 语句,返回结果为整型
     * 主要用于执行非查询语句
     * @param cmdText SQL 语句
     * @return 非负数:正常执行; -1:执行错误; -2:连接错误
     */
    public static int ExecSql(Connection conn, String cmdText)
    {
        Statement stmt = getStatement(conn);
        if (stmt == null)
        {
            return -2;
        }
        int i;
        try
        {
            i = stmt.executeUpdate(cmdText);

        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
           
            i = -1;
        }
        close(stmt);
        return i;
    }

    /**
     * 执行 SQL 语句,返回结果为整型
     * 主要用于执行非查询语句
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return 非负数:正常执行; -1:执行错误; -2:连接错误
     */
    //非常好用
    public static int ExecSql(String cmdText, Object[] cmdParams)
    {
        PreparedStatement pstmt = getPreparedStatement(cmdText, cmdParams);
        if (pstmt == null)
        {
            return -2;
        }
        int i;
        try
        {
            i = pstmt.executeUpdate();
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
           i = -1;
        }
        closeConnection(pstmt);
        return i;
    }

    /**
     * 执行 SQL 语句,返回结果为整型
     * 主要用于执行非查询语句
     * @param conn 数据库连接
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return 非负数:正常执行; -1:执行错误; -2:连接错误
     */
    public static int ExecSql(Connection conn, String cmdText, Object[] cmdParams)
    {
        PreparedStatement pstmt = getPreparedStatement(conn, cmdText, cmdParams);
        if (pstmt == null)
        {
            return -2;
        }
        int i;
        try
        {
            i = pstmt.executeUpdate();

        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            i = -1;
        }
        close(pstmt);
        return i;
    }

    /**
     * 返回结果集的第一行的一列的值,其他忽略
     * @param cmdText SQL 语句
     * @return
     */
    public static Object ExecScalar(String cmdText)
    {
        ResultSet rs = getResultSet(cmdText);
        Object obj = getScalar(rs);
        closeConnection(rs);
        return obj;
    }

    /**
     * 返回结果集的第一行的一列的值,其他忽略
     * @param conn 数据库连接
     * @param cmdText SQL 语句
     * @return
     */
    public static Object ExecScalar(Connection conn, String cmdText)
    {
        ResultSet rs = getResultSet(conn, cmdText);
        Object obj = getScalar(rs);
        closeEx(rs);
        return obj;
    }

    /**
     * 返回结果集的第一行的一列的值,其他忽略
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return
     */
    public static Object ExecScalar(String cmdText, Object[] cmdParams)
    {
        ResultSet rs = getResultSet(cmdText, cmdParams);
        Object obj = getScalar(rs);
        closeConnection(rs);
        return obj;
    }

    /**
     * 返回结果集的第一行的一列的值,其他忽略
     * @param conn 数据库连接
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return
     */
    public static Object ExecScalar(Connection conn, String cmdText, Object[] cmdParams)
    {
        ResultSet rs = getResultSet(conn, cmdText, cmdParams);
        Object obj = getScalar(rs);
        closeEx(rs);
        return obj;
    }

    /**
     * 返回一个 ResultSet
     * @param cmdText SQL 语句
     * @return
     */
    public static ResultSet getResultSet(String cmdText)
    {
        Statement stmt = getStatement();
        if (stmt == null)
        {
            return null;
        }
        try
        {
            return stmt.executeQuery(cmdText);
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
           closeConnection(stmt);
        }
        return null;
    }

    /**
     * 返回一个 ResultSet
     * @param conn
     * @param cmdText SQL 语句
     * @return
     */
    public static ResultSet getResultSet(Connection conn, String cmdText)
    {
        Statement stmt = getStatement(conn);
        if (stmt == null)
        {
            return null;
        }
        try
        {
            return stmt.executeQuery(cmdText);
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            close(stmt);
        }
        return null;
    }

    /**
     * 返回一个 ResultSet
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return
     */
    public static ResultSet getResultSet(String cmdText, Object[] cmdParams)
    {
        PreparedStatement pstmt = getPreparedStatement(cmdText, cmdParams);
        if (pstmt == null)
        {
            return null;
        }
        try
        {
            return pstmt.executeQuery();
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            closeConnection(pstmt);
        }
        return null;
    }

    /**
     * 返回一个 ResultSet
     * @param conn 数据库连接
     * @param cmdText 需要 ? 参数的 SQL 语句
     * @param cmdParams SQL 语句的参数表
     * @return
     */
    public static ResultSet getResultSet(Connection conn, String cmdText, Object[] cmdParams)
    {
        PreparedStatement pstmt = getPreparedStatement(conn, cmdText, cmdParams);
        if (pstmt == null)
        {
            return null;
        }
        try
        {
            return pstmt.executeQuery();
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
            close(pstmt);
        }
        return null;
    }

    public static Object getScalar(ResultSet rs)
    {
        if (rs == null)
        {
            return null;
        }
        Object obj = null;
        try
        {
            if (rs.next())
            {
                obj = rs.getObject(1);
            }
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
        }
        return obj;
    }
 
    private static void close(Object obj)
    {
        if (obj == null)
        {
            return;
        }
        try
        {
            if (obj instanceof Statement)
            {
                ((Statement) obj).close();
            } else if (obj instanceof PreparedStatement)
            {
                ((PreparedStatement) obj).close();
            } else if (obj instanceof ResultSet)
            {
                ((ResultSet) obj).close();
            } else if (obj instanceof Connection)
            {
                ((Connection) obj).close();
            }
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
       }
    }

    private static void closeEx(Object obj)
    {
        if (obj == null)
        {
            return;
        }

        try
        {
            if (obj instanceof Statement)
            {
                ((Statement) obj).close();
            } else if (obj instanceof PreparedStatement)
            {
                ((PreparedStatement) obj).close();
            } else if (obj instanceof ResultSet)
            {
                ((ResultSet) obj).getStatement().close();
            } else if (obj instanceof Connection)
            {
                ((Connection) obj).close();
            }
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
        }

    }

    private static void closeConnection(Object obj)
    {
        if (obj == null)
        {
            return;
        }
        try
        {
            if (obj instanceof Statement)
            {
                ((Statement) obj).getConnection().close();
            } else if (obj instanceof PreparedStatement)
            {
                ((PreparedStatement) obj).getConnection().close();
            } else if (obj instanceof ResultSet)
            {
                ((ResultSet) obj).getStatement().getConnection().close();
            } else if (obj instanceof Connection)
            {
                ((Connection) obj).close();
            }
        } catch (SQLException ex)
        {
            //Logger.getLogger(DBHelper.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println(ex.getMessage());
       }
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>登录</title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  
  <body>
     <center>
    <form name="f1" action="login.jsp" >
      登录名:<input type="text" name="uid"><br>
      密码:<input type="password" name="pwd"><br>
      <input type="submit" value="提交">
      <input type="reset" value="重置"> 
    </form>
    </center>
  </body>
</html>

<%@ page language="java" import="java.util.*,java.sql.*,DBHelper.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title></title>
    <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  </head>
  <body>
  <%
    String SQL="SELECT * FROM user WHERE userName=? AND password=?";
    String uid=request.getParameter("uid");
    String pwd=request.getParameter("pwd");
    Object[] params=new Object[]{uid,pwd};
    ResultSet rs=DBHelper.getResultSet(SQL,params);
    if(rs.next())
    out.print("登录成功");
    else
    out.print("登录失败");
    rs.close();
    %>
  
  </body>
</html>