Js:
<script type="text/javascript">
var xmlHttpRequest;
//创建XMLHttpRequest对象
function createXMLHttpRequest()
{
if(xmlHttpRequest == null)
{
//对于 Mozila 浏览器
if(window.XMLHttpRequest)
{
xmlHttpRequest = new XMLHttpRequest();
}
//对于 IE 浏览器
else if(window.ActiveXObject)
{
try
{
xmlHttpRequest = new ActiveXObject("Msxml2.XMLHTTP");
}
catch(e)
{
try
{
xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
}
catch(e)
{
}
}
}
}
}
//发送请求
function sendRequest()
{
var name = document.getElementById("name");
var pass = document.getElementById("pass");
var nameValue = name.value;
var passValue = pass.value;
createXMLHttpRequest();
var url = "LoginServlet";
xmlHttpRequest.open("POST", url, true);
xmlHttpRequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttpRequest.onreadystatechange = processResponse;
xmlHttpRequest.send("name="+nameValue+"&pass="+passValue);
}
//处理服务器响应
function processResponse()
{
if(xmlHttpRequest.readyState == 4)
{
if(xmlHttpRequest.status == 200)
{
document.getElementById("msg").innerHTML = xmlHttpRequest.responseText;
}
}
}
function check()
{
var name = document.getElementById("name");
var pass = document.getElementById("pass");
var nameValue = name.value;
var passValue = pass.value;
var msg = "";
if(nameValue == null || nameValue == "")
{
msg += "用户名为空 \n";
}
if(passValue == null || passValue == "")
{
msg += "密码为空 \n";
}
if(msg == null || msg == "")
{
sendRequest();
}
else
{
document.getElementById("msg").innerHTML = msg;
}
}
</script>
Servlet:
public void service(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
String name = request.getParameter("name");
String pass = request.getParameter("pass");
if (name == null || pass == null) {
PrintWriter out = response.getWriter();
out.println("用户名和密码都不能为空");
}
if(ChatService.instance().validLogin(name, pass)){
forward("/chat.jsp",request,response);
}else{
PrintWriter out = response.getWriter();
out.println("用户名或密码错误");
}
}
private void forward(String url, HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
ServletContext sc = getServletConfig().getServletContext();
RequestDispatcher rd = sc.getRequestDispatcher(url);
rd.forward(request, response);
}