為什么在serlvet層會(huì)提示queryMessageList(String,String)這個(gè)方法不存在呢？

//service層代碼

package com.imooc.service;

import java.util.List;

import com.imooc.bean.Message;

import com.imooc.dao.MessageDao;

/*

?* 列表相關(guān)的業(yè)務(wù)功能,因?yàn)橐话悴恢苯诱{(diào)dao層的，都是要經(jīng)過(guò)service來(lái)調(diào)用

?*/

public class ListService {

public List<Message> queryMessageList(String command,String description){

MessageDao messageDao=new MessageDao();

return messageDao.queryMessageList(command, description);

}

}

//servlet層代碼

package com.imooc.servlet;

import java.io.IOException;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.imooc.bean.Message;

import com.imooc.service.ListService;

/**

?*列表頁(yè)面的初始化?

?*

?*/

@SuppressWarnings("serial")

public class ListServlet extends HttpServlet {

@Override

protected void doGet(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

//設(shè)置編碼

req.setCharacterEncoding("UTF-8");

//接受頁(yè)面的值

String command=req.getParameter("command");

String description=req.getParameter("description");

//向頁(yè)面?zhèn)髦?/p>

req.setAttribute("command", command);

req.setAttribute("description", description);

ListService listService=new ListService();

List<Message> messageList=new ArrayList<Message>();

messageList=listService.queryMessageList(command, description);

? ? ?req.setAttribute("messageList", messageList);

//在上面用jdbc把數(shù)據(jù)庫(kù)取出來(lái)之后放在messageList里面，然后就可以轉(zhuǎn)發(fā)了，轉(zhuǎn)發(fā)到由req帶到前臺(tái)去使用請(qǐng)求轉(zhuǎn)發(fā)，就是servlet那里傳過(guò)來(lái)的請(qǐng)求會(huì)直接轉(zhuǎn)給這個(gè)頁(yè)面來(lái)處理

req.getRequestDispatcher("/WEB-INF/jsp/background/list.jsp").forward(req, resp);

}

@Override

protected void doPost(HttpServletRequest req, HttpServletResponse resp)

throws ServletException, IOException {

this.doGet(req, resp);

}

}