servlet中请求的资源不允许使用指定的http方法

Question

我使用注释编写控制器来映射控制器。 在页面jsp我有一个ajax请求到控制器但我得到错误 “ 类型：状态报告

消息：此URL不支持HTTP方法GET

description：请求的资源不允许使用指定的HTTP方法。 “ 为什么会这样？

控制器类：

package controllers;
import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import model.AntiXss;
import model.HibernateToDoListDAO;
import model.Items;
import model.ToDoListDAOException;
import model.User;

@WebServlet("/DeleteMessage/*")
public class DeleteMessageController extends HttpServlet{
    private static final long serialVersionUID = 1L;

    HttpSession session = null;
    User user = null;
    Items item = null;
    List<Items> items = null;
    String message;
    HibernateToDoListDAO actions = HibernateToDoListDAO.getInstance();

    public DeleteMessageController()
    {
        super();
    }

    @Override
    @SuppressWarnings("unchecked")
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException 
    {
        session = request.getSession(false);
        if(session == null)
        {
            response.sendRedirect("error.jsp");
        }
        try{
            message = request.getParameter("item");
            if(AntiXss.isUsername(message) == false )
            {
                if(session != null){
                    session.invalidate();
                }
                response.sendRedirect("error.jsp");
            }
            else
            {
                items = (List<Items>)session.getAttribute("listItems");
                user = (User)session.getAttribute("user");
                for(Items newItem : items)
                {
                    if(newItem.getMessage() == message && newItem.getUsername() == user.getUsername())
                    {
                        item = newItem;
                    }
                }
                actions.deleteItems(item);
                items = actions.getItems(user.getUsername());
                session.setAttribute("listItems", items);
                request.getRequestDispatcher("Index.jsp").forward(request, response);
            }
        }catch(ToDoListDAOException e){
            e.printStackTrace();
        }
    }
}

和jsp页面:(我在这里只是ajax请求）;

var xmlhttp = new XMLHttpRequest();
var item = "test";
if((txtSearch(item, item.length)) == 1)
{
    var url = "DeleteMessage";
    try
    {
        xmlhttp.open("post",url,true);
        xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        xmlhttp.send("item=" + item);

    }catch(e){
        alert("unable to connect to server");
    }
}