How can I authenticate a User In Windows Active Directory?

Question

I need to authenticate a user in Windows Active Directory, but I found use the code below will return true if the user name and password are both correct and false if one of them is wrong. But when I input a user name which is not exist in Active Driectory with a blank password, it will also return true. What shall I do? Ask every user must input a password withnot blank?
Please give me some help to solve this problem. Thanks a lot.
Code:
private Context ctx = null;
Hashtable env = new Hashtable ();
boolean isValid = false;
try {
this.setEnvironmentProperties();
String domainName = AuthenticateResources.getString("mydomain.com");
//set the name of domain with the user name
String fullName = name + "@" + domainName;
env.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.ldap.LdapCtxFactory");
env.put(Context.PROVIDER_URL,"ldap://mydomain:389");
env.put(Context.SECURITY_AUTHENTICATION,"simple");
//set user related information
env.put(Context.SECURITY_PRINCIPAL, fullName);
//set user password
env.put(Context.SECURITY_CREDENTIALS, password);
//validate user
ctx = new InitialDirContext(env);
isValid = true;
}catch (AuthenticationException ex){
isValid = false;
catch (NamingException ex) {
throw ex;
}finally{
this.freeContext();
return isValid;

Answer 1

This is usually a problem if Anonymous Binding is enabled. I have faced this in other Directory Servers, but I am not familiar with Active Directory.
I think by default Active Directory disables Anonymous Binding, but you may want to check.