我是Java Servlet和Ajax的新手。我想验证用户是否输入了正确的密码，但是ajax中的就绪状态更改永远不会达到4。它还必须检查电子邮件/用户名是否正确或错误，但代码永远不会达到onreadystatechange()功能表示它永远不会变成4.请帮助。
这里是HTML代码：
<!DOCTYPE HTML>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Notes Finder</title>
<script type="text/javascript">
function verify()
{
var email=document.forms["Login"]["Email"].value;
var password=document.forms["Login"]["Password"].value;
if(email.length==0)
{
alert("Email is not submitted.Please check that you have entered the Email");
return false;
}
if(password.length==0) {
alert("Password is not submitted.Please check that you have entered the Password");
return false;
}
check_email();
}
</script>
</head>
<body>
<form name="Login" method="post" onsubmit="return verify()" id="Login" >
<p>Email:</p><input type="text" name="Email" placeholder="UserName"/><p id="emailpara"
style="color:red;"></p><br><br>
<p>Password:</p><input type="password" name="Password" placeholder="Password"/><p
id="passwordpara" style="color:white"></p><br><br>
<input type="submit" value="Submit"/>
</form>
<script type="text/javascript">
function check_email()
{
var make_ajax_request=new XMLHttpRequest();
var original_form=document.getElementById("Login");
var form=new FormData(original_form);
make_ajax_request.onreadystatechange=function()
{
if(make_ajax_request.readystate==4&&make_ajax_request.status==200)
{
alert("Inside check_email");
var returntext=this.responsetext();
returntext.toLowerCase();
document.getElementbyId("emailpara").innerHTML=returntext;
if(returntext.localeCompare("1"))
{
document.getElementbyId("emailpara").innerHTML="";
document.getElementbyId("passwordpara").innerHTML="";
}
else if(returntext.localeCompare("2"))
{
document.getElementbyId("emailpara").innerHTML="Email not found.Please verify again";
}
else if(returntext.localeCompare("3"))
{
document.getElementbyId("passwordpara").innerHTML="Incorrect Password.Please check that
you have entered the correct password";
}
}
};
make_ajax_request.open("post","login",true);
make_ajax_request.send(form);
}
</script>
</body>
</html>
这是servlet代码：
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
response.setContentType("text/html");
PrintWriter writer=response.getWriter();
System.out.println("Request received12");
email=request.getParameter("Email");
password=request.getParameter("Password");
System.out.println("Email:"+email+"\nPassword:"+password);
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con=DriverManager.getConnection(url, user, pass);
Statement statement=con.createStatement();
rs=statement.executeQuery("Select email,password_ from "+table_name+" where email='"+email+"'");
meta=rs.getMetaData();
if(!rs.next())
{
writer.write("2");
}
else
{
//This is the method used for hashing the password for comparison of password
MessageDigest sha512=MessageDigest.getInstance("SHA-512");
sha512.update(salt.getBytes(StandardCharsets.UTF_8));
byte[] messagedigest=sha512.digest(password.getBytes(StandardCharsets.UTF_8));
StringBuilder temp=new StringBuilder();
for(int i=0;i<messagedigest.length;i++)
{
temp.append(Integer.toString((messagedigest[i] & 0xff) + 0x100, 16).substring(1));
}
hashedpassword=temp.toString();
System.out.println("Hashed Password="+hashedpassword);
//Password has been hashed successfully
if(hashedpassword.equals(rs.getString("password_")))
{
Cookie cookie=new Cookie(email,password);
response.addCookie(cookie);
System.out.println("Password has been matched");
writer.write("1");
response.sendRedirect("");
}
else
{
writer.write("3");
System.out.println("Password has been unmatched");
}
}
writer.close();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
throw new IllegalStateException(e);
} catch (SQLException e) {
// TODO Auto-generated catch block
throw new IllegalStateException(e);
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
throw new IllegalStateException(e);
}
}
以上代码返回分配了特定代码以检查错误的数字。
尝试以下操作