Java里面Windows的身份验证

在Java里面去读取Windows域帐号，这样一个小的Web系统就不需要再建立一套帐户和密码了。
在asp.net里面这个是很容易实现的，但是Java里面不知道该如何去取得呢？

<%
String auth = request.getHeader("Authorization");
if (auth == null)
{
response.setStatus(response.SC_UNAUTHORIZED);
response.setHeader("WWW-Authenticate", "NTLM");
response.flushBuffer();
return;
}
if (auth.startsWith("NTLM "))
{
byte[] msg = new sun.misc.BASE64Decoder().decodeBuffer(auth.substring(5));
int off = 0, length, offset;
if (msg[8] == 1)
{
byte z = 0;
byte[] msg1 = {(byte)'N', (byte)'T', (byte)'L', (byte)'M', (byte)'S', (byte)'S', (byte)'P', z,(byte)2, z, z, z, z, z, z, z,(byte)40, z, z, z, (byte)1, (byte)130, z, z,z, (byte)2, (byte)2, (byte)2, z, z, z, z, z, z, z, z, z, z, z, z};
response.setHeader("WWW-Authenticate", "NTLM " + new sun.misc.BASE64Encoder().encodeBuffer(msg1));
response.sendError(response.SC_UNAUTHORIZED);
return;
}
else if (msg[8] == 3)
{
off = 30;

length = msg[off+17]*256 + msg[off+16];
offset = msg[off+19]*256 + msg[off+18];
String remoteHost = new String(msg, offset, length);

length = msg[off+1]*256 + msg[off];
offset = msg[off+3]*256 + msg[off+2];
String domain = new String(msg, offset, length);

length = msg[off+9]*256 + msg[off+8];
offset = msg[off+11]*256 + msg[off+10];
String username = new String(msg, offset, length);

out.println("Username:"+username+"<BR>");
out.println("RemoteHost:"+remoteHost+"<BR>");
out.println("Domain:"+domain+"<BR>");
}
}
%>

就是有点慢