从数据库中取出的密码或者用户名后会带有一串的空格
所以equals比较时会显示错误
使用trim（）函数去除空格就可以了
运行成功代码如下：
login.jsp
<%@ page import="java.sql.*" language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>登录界面</title></head><body><center><h1 style="color:red">登录</h1><form id="indexform" name="indexForm" action="logincheck.jsp" method="post"><table border="0"><tr><td>账号：</td><td><input type="text" name="username"></td></tr><tr><td>密码：</td><td><input type="password" name="password"></td></tr></table><br><input type="submit" value="登录" style="color:#BC8F8F"></form></center></body></html>
logincheck.jsp
<%@page import="Bean.DBBean"%><%@ page import="java.sql.*" language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>Insert title here</title></head><body><jsp:useBean id="db" class="Bean.DBBean" scope="page"/><%request.setCharacterEncoding("UTF-8");String username=(String)request.getParameter("username");String password=(String)request.getParameter("password");//取出login.jsp的值//下面是数据库操作 *代表所有值db.getconn();String sql="select * from lhT where username="+"'"+username+"';";//定义一个查询语句ResultSet rs=db.executeQuery(sql);//运行上面的语句if(rs.next()){/* if(password.equals(rs.getString(2))){} */Boolean c= (password,rs.getString("password"));if(c){response.sendRedirect("loginsuccess.jsp");}else{out.print("<script language='javaScript'> alert('密码错误');</script>");response.setHeader("refresh", "0;url=login.jsp");}}else {out.print("<script language='javaScript'> alert('请输入用户名——else');</script>");response.setHeader("refresh", "0;url=login.jsp");}%></body></html>
loginsussess.jsp
<%@ page import="java.sql.*" language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Insert title here</title></head><body><h1>登录成功 </h1></body></html>
DBBean.java
package Bean;import java.sql.*;public class DBBean {private String driverStr = "com.microsoft.sqlserver.jdbc.SQLServerDriver";private String connStr = "jdbc:sqlserver://localhost:1433; DatabaseName=lhsjk";private String dbusername = "sa";private String dbpassword = "123456";private Connection conn = null;private Statement stmt = null;public DBBean() {}public boolean com(String a,String b){a=a.trim();b=b.replaceAll("\\s*", "");System.out.println(a);System.out.println(b);if(a.equals(b)){return true;}elsereturn false;}public void getconn(){try{Class.forName(driverStr);conn = DriverManager.getConnection(connStr, dbusername, dbpassword);stmt = conn.createStatement();} catch (Exception ex) {System.out.println(ex.getMessage());System.out.println("数据连接失败！");} }public int executeUpdate(String s) {int result = 0;System.out.println("--更新语句:"+s+"\n");try {result = stmt.executeUpdate(s);} catch (Exception ex) {System.out.println("执行更新错误！");}return result;}public ResultSet executeQuery(String s) {ResultSet rs = null;System.out.print("--查询语句:"+s+"\n");try {rs = stmt.executeQuery(s);} catch (Exception ex) {System.out.println("ִ执行查询错误！");}return rs;}public void execQuery(String s){try {stmt.executeUpdate(s);} catch (SQLException e) {// TODO Auto-generated catch blockSystem.out.println("执行插入错误！");}}public void close() {try {stmt.close();conn.close();} catch (Exception e) {}}}
文件结构目录：
