本文介绍了一个使用Java进行数据库连接的示例，并演示了如何实现用户登录验证功能。通过加载Microsoft SQL Server JDBC驱动，建立数据库连接，执行SQL查询及更新操作，并在登录页面验证用户名与密码。
conn.java
package beans;import java.sql.*;
public class connDB...{
Connection conn=null; Statement stmt=null; ResultSet rs=null;
public connDB()...{ try...{ Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver"); }catch(java.lang.ClassNotFoundException e)...{ System.err.println(e.getMessage());
} } /** *//*************************************************** *method name: executeQuery() *功能:执行查询操作 *return value: ResultSet *2005-12-05****************************************************/ public ResultSet executeQuery(String sql)...{ try...{ conn=DriverManager.getConnection("jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=db_bookmanage;user=sa;password="); stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); rs=stmt.executeQuery(sql); }catch(SQLException ex)...{ System.err.println(ex.getMessage()); } return rs; }/** *//*************************************************** *method name: executeUpdate() *功能:执行更新操作 *return value: int *2005-12-05****************************************************/ public int executeUpdate(String sql)...{ int result=0; try...{ conn=DriverManager.getConnection("jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=db_bookmanage;user=sa;password="); stmt=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); result=stmt.executeUpdate(sql); }catch(SQLException ex)...{ result=0; } return result; } /** *//*************************************************** *method name: close() *功能:关闭数据库链接 *return value: void *2005-12-05****************************************************/ public void close()...{ try ...{ if (rs != null) rs.close(); } catch (Exception e) ...{ e.printStackTrace(System.err); } try ...{ if (stmt != null) stmt.close(); } catch (Exception e) ...{ e.printStackTrace(System.err); } try ...{ if (conn != null) ...{ conn.close(); } } catch (Exception e) ...{ e.printStackTrace(System.err); } }login.jsp
<%@ page contentType="text/html; charset=GB2312"%><%@ page import="java.sql.*"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>系统登陆</title> </head> <body> <%String username=request.getParameter("uid");String password=request.getParameter("upwd");if(username != null && !username.equals(""))...{try...{ /**//* * 连接数据库 */ Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver"); Connection conn=DriverManager.getConnection("jdbc:microsoft:sqlserver://localhost:1433;DatabaseName=CheckUser;user=sa;password="); Statement stmt=conn.createStatement(); String sql = "select * from users where username='" + username + "'"; sql += " and password='" + password + "'"; //准备查询语句 ResultSet rs=stmt.executeQuery( sql ); if( rs.next() )...{ session.setAttribute("login","ok"); //验证通过之后，跳转到后续页面 session.setAttribute("uname",username);%><jsp:forward page="main.jsp"/> <% }else out.println("错误的用户名和密码"); //验证未通过，显示错误信息 out.println("<a href=index.html>返回</a>"); }catch(Exception ee)...{ ee.printStackTrace(); } }else...{ out.println("请先登录！"); //验证未通过，显示错误信息 out.println("<a href=index.html>返回</a>"); 
}%> </body></html>username != null && !username.equals("")
session.getAttribute("login")==null || !session.getAttribute("login").equals("ok")
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