小弟初学AJAX，遇到404问题，baidu，google都不能解决。
附上源码，哪位大哥给点意见，多谢多谢。

web.xml
[code="xml"]

RefreshModelList
ajax.RefreshModelListServlet


RefreshModelList
/RefreshModelList

[/code]
RefreshModelListServlet.java
[code="java"]
package ajax;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class RefreshModelListServlet extends HttpServlet{

/**
 * 
 */
private static final long serialVersionUID = 1L;

private static List availableModels = new ArrayList();

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException{
    response.setContentType("text/html; charset=UTF-8");
    int modelYear = Integer.parseInt(request.getParameter("modelYear"));
    String make = request.getParameter("make");

    StringBuffer results = new StringBuffer("<models>");
    MakeModelYear availableModel = null;

    for(Iterator it = availableModels.iterator(); it.hasNext();){
        availableModel = (MakeModelYear)it.next();
        if(availableModel.modelYear == modelYear){
            if(availableModel.make.equals(make)){
                results.append("<model>");
                results.append("availableModel.model");
                results.append("</model>");
            }

        }
    }
    results.append("</models>");
    response.setContentType("text/xml");
    response.getWriter().write(results.toString());

}



@Override
public void init() throws ServletException {

    availableModels.add(new MakeModelYear(2006, "Dodge", "Charger"));
    availableModels.add(new MakeModelYear(2006, "Dodge", "Magnum"));
    availableModels.add(new MakeModelYear(2006, "Dodge", "Ram"));
    availableModels.add(new MakeModelYear(2006, "Dodge", "Viper"));
    availableModels.add(new MakeModelYear(1995, "Dodge", "Avenger"));
    availableModels.add(new MakeModelYear(1995, "Dodge", "Intrepid"));
    availableModels.add(new MakeModelYear(1995, "Dodge", "Neon"));
    availableModels.add(new MakeModelYear(1995, "Dodge", "Spirit"));
    availableModels.add(new MakeModelYear(1985, "Dodge", "Aries"));
    availableModels.add(new MakeModelYear(1985, "Dodge", "Daytona"));
    availableModels.add(new MakeModelYear(1985, "Dodge", "Omni"));
    availableModels.add(new MakeModelYear(1970, "Dodge", "Challenger"));
    availableModels.add(new MakeModelYear(1970, "Dodge", "Charger"));
    availableModels.add(new MakeModelYear(1970, "Dodge", "Coronet"));
    availableModels.add(new MakeModelYear(1970, "Dodge", "Dart"));

    availableModels.add(new MakeModelYear(2006, "Chevrolet", "Colorado"));
    availableModels.add(new MakeModelYear(2006, "Chevrolet", "Corvette"));
    availableModels.add(new MakeModelYear(2006, "Chevrolet", "Equinox"));
    availableModels.add(new MakeModelYear(2006, "Chevrolet", "Monte Carlo"));
    availableModels.add(new MakeModelYear(1995, "Chevrolet", "Beretta"));
    availableModels.add(new MakeModelYear(1995, "Chevrolet", "Camaro"));
    availableModels.add(new MakeModelYear(1995, "Chevrolet", "Cavalier"));
    availableModels.add(new MakeModelYear(1995, "Chevrolet", "Lumina"));
    availableModels.add(new MakeModelYear(1985, "Chevrolet", "Cavalier"));
    availableModels.add(new MakeModelYear(1985, "Chevrolet", "Chevette"));
    availableModels.add(new MakeModelYear(1985, "Chevrolet", "Celebrity"));
    availableModels.add(new MakeModelYear(1985, "Chevrolet", "Citation II"));
    availableModels.add(new MakeModelYear(1970, "Chevrolet", "Bel Air"));
    availableModels.add(new MakeModelYear(1970, "Chevrolet", "Caprice"));
    availableModels.add(new MakeModelYear(1970, "Chevrolet", "Chevelle"));
    availableModels.add(new MakeModelYear(1970, "Chevrolet", "Monte Carlo"));

    availableModels.add(new MakeModelYear(2006, "Pontiac", "G6"));
    availableModels.add(new MakeModelYear(2006, "Pontiac", "Grand Prix"));
    availableModels.add(new MakeModelYear(2006, "Pontiac", "Solstice"));
    availableModels.add(new MakeModelYear(2006, "Pontiac", "Vibe"));
    availableModels.add(new MakeModelYear(1995, "Pontiac", "Bonneville"));
    availableModels.add(new MakeModelYear(1995, "Pontiac", "Grand Am"));
    availableModels.add(new MakeModelYear(1995, "Pontiac", "Grand Prix"));
    availableModels.add(new MakeModelYear(1995, "Pontiac", "Firebird"));
    availableModels.add(new MakeModelYear(1985, "Pontiac", "6000"));
    availableModels.add(new MakeModelYear(1985, "Pontiac", "Fiero"));
    availableModels.add(new MakeModelYear(1985, "Pontiac", "Grand Prix"));
    availableModels.add(new MakeModelYear(1985, "Pontiac", "Parisienne"));
    availableModels.add(new MakeModelYear(1970, "Pontiac", "Catalina"));
    availableModels.add(new MakeModelYear(1970, "Pontiac", "GTO"));
    availableModels.add(new MakeModelYear(1970, "Pontiac", "LeMans"));
    availableModels.add(new MakeModelYear(1970, "Pontiac", "Tempest"));
}



@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    processRequest(req, resp);
}


private static class MakeModelYear{

    private int modelYear;
    private String make;
    private String model;

    public MakeModelYear (int modelYear,String make,String model){
    this.modelYear = modelYear;
    this.make = make;
    this.model = model;
}
}

}
[/code]

dynamic.html
[code="html"]
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

Dynamically Filling Lists var xmlHttp; function createXMLHttpRequest() { if (window.ActiveXObject) { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } else if (window.XMLHttpRequest) { xmlHttp = new XMLHttpRequest(); } } function refreshModelList() { var make = document.getElementById("make").value; var modelYear = document.getElementById("modelYear").value; if (make == "" || modelYear == "") { clearModelList(); return; } var url = "/RefreshModelList?" + createQueryString(make, modelYear) + "&ts=" + new Date().getTime(); [color=red]alert(url);[/color]//这里有值 createXMLHttpRequest(); xmlHttp.onreadystatechange = handleStateChange; xmlHttp.open("GET", url, false); xmlHttp.send(null); } function createQueryString(make, modelYear) { var queryString = "make=" + make + "&modelYear=" + modelYear; return queryString; } function handleStateChange() { if (xmlHttp.readyState == 4) { [color=red]alert(xmlHttp.status);[/color] //这里总是404 if (xmlHttp.status == 200) { updateModelsList(); } } } function updateModelsList() { clearModelsList(); var models = document.getElementById("models"); var results = xmlHttp.responseXML.getElementsByTagName("model"); var option = null; for ( var i = 0; i < results.length; i++) { option = document.createElement("option"); option.appendChild(document .createTextNode(result[i].firstChild.nodeValue)); models.appendChild(option); } } function clearModelList() { var models = document.getElementById("models"); while (models.childNodes.length > 0) { models.removeChild(models.childNode[0]); } }

Select Model Year and Make

Model Year: id="modelYear" onchange="refreshModelList();">
Select One
2006
1995
1985
1970


Make: id="make" onchange="refreshModelList();">
Select One
Chevrolet
Doge
Pontiac

    </select> <br> <br> <span style="font-weight: bold;">Models: </span>
    <br> <select id="models" size="6" style="width: 300px;"></select>
</form>

[/code]

明显路径错了嘛
url ="<%=request.getContextPath()%>/RefreshModelList?" + createQueryString(make, modelYear)+ "&ts=" + new Date().getTime();

那你就把地址写死在这里呗，也不能只信书啊，程序告诉你了，这个url没有肯定是没有的嘛。。。