防止用户非法登录又一法
类别: JSP教程 
由于用户名及密码都是由a-z,A-Z,0-9这几字符组成， 我参考了一下正则表达式的算法，故有已下想法： 把用户输入的用户名及密码判断一下，看是否是这几个字符组成， 如果是，进行登录验证,否则提示有非法字符
代码如下:
//login.jsp
<%@ page contentType="text/html; charset=GBK" language="java" import="java.io.*" errorPage="error.jsp" %>
<%!
boolean regex(String str){
java.util.regex.Pattern p=null; //正则表达式
java.util.regex.Matcher m=null; //操作的字符串
boolean value=true;
try{
p = java.util.regex.Pattern.compile("[^0-9A-Za-z]");
m = p.matcher(str);
if(m.find()) {
value=false;
}
}catch(Exception e){}
return value;
}
%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK">
<title>无标题文档</title>
</head>
<body>
<table width="100%" height="100%" border="0">
<tr>
<td align="center" valign="middle">
<% String action=request.getParameter("action");
if (action!=null&&action.equals("login")){
String username=request.getParameter("username");
String password=request.getParameter("password");
if(!regex(username)||!regex(password)){
out.println("<Script language=´javascript´>");
out.println("alert(´1.用户名只能是a-z,A-Z,0-9的字符\\n2.密码只能是a-z,A-Z,0-9的字符\\n3.不允许空格´)");
out.println("history.go(-1)");
out.println("</script>");
out.print("用户名只能是a-z,A-Z,0-9的字符");
return;//跳出程序
}
out.println(action);//登录验证
out.println("用户名是"+username+"<br>");
out.println("密码"+password);
}
else{
%>
<form name="form1" method="post" action="#">
<table width="70%" border="0">
<tr>
<td>username</td>
<td><input name="username" type="text" id="username">
</td>
</tr>
<tr>
<td>password</td>
<td><input name="password" type="text" id="password"></td>
</tr>
<tr>
<td> </td>
<td><input name="action" type="hidden" id="action" value="login">
用户名及密码只能是a-z,A-Z,0-9的字符</td>
</tr>
<tr>
<td><input type="submit" name="Submit" value=" O K "></td>
<td><input type="reset" name="Submit2" value="Cancle"></td>
</tr>
</table>
</form><% } %></td>
</tr>
</table>
</body>
</html>
代码如下:
//login.jsp
<%@ page contentType="text/html; charset=GBK" language="java" import="java.io.*" errorPage="error.jsp" %>
<%!
boolean regex(String str){
java.util.regex.Pattern p=null; //正则表达式
java.util.regex.Matcher m=null; //操作的字符串
boolean value=true;
try{
p = java.util.regex.Pattern.compile("[^0-9A-Za-z]");
m = p.matcher(str);
if(m.find()) {
value=false;
}
}catch(Exception e){}
return value;
}
%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK">
<title>无标题文档</title>
</head>
<body>
<table width="100%" height="100%" border="0">
<tr>
<td align="center" valign="middle">
<% String action=request.getParameter("action");
if (action!=null&&action.equals("login")){
String username=request.getParameter("username");
String password=request.getParameter("password");
if(!regex(username)||!regex(password)){
out.println("<Script language=´javascript´>");
out.println("alert(´1.用户名只能是a-z,A-Z,0-9的字符\\n2.密码只能是a-z,A-Z,0-9的字符\\n3.不允许空格´)");
out.println("history.go(-1)");
out.println("</script>");
out.print("用户名只能是a-z,A-Z,0-9的字符");
return;//跳出程序
}
out.println(action);//登录验证
out.println("用户名是"+username+"<br>");
out.println("密码"+password);
}
else{
%>
<form name="form1" method="post" action="#">
<table width="70%" border="0">
<tr>
<td>username</td>
<td><input name="username" type="text" id="username">
</td>
</tr>
<tr>
<td>password</td>
<td><input name="password" type="text" id="password"></td>
</tr>
<tr>
<td> </td>
<td><input name="action" type="hidden" id="action" value="login">
用户名及密码只能是a-z,A-Z,0-9的字符</td>
</tr>
<tr>
<td><input type="submit" name="Submit" value=" O K "></td>
<td><input type="reset" name="Submit2" value="Cancle"></td>
</tr>
</table>
</form><% } %></td>
</tr>
</table>
</body>
</html>
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