js轮询

我是在用于点击支付的时候开启轮询，结束了 就停止

简单例子

package com.kaishengit.dao;

import com.kaishengit.entity.Message;
import com.kaishengit.util.DbHelp;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import java.util.List;

public class MessageDao {

    public List findAll() {
        String sql = "select * from t_message order by id desc";
        return DbHelp.query(sql,new BeanListHandler<>(Message.class));
    }

    public List findByMaxId(int maxId) {
        String sql = "select * from t_message where id > ? order by id desc";
        return DbHelp.query(sql,new BeanListHandler<>(Message.class),maxId);
    }
}

package com.kaishengit.entity;

public class Message {

    private Integer id;
    private String message;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

package com.kaishengit.service;

import com.kaishengit.dao.MessageDao;
import com.kaishengit.entity.Message;

import java.util.List;

public class MessageService {

    private MessageDao messageDao = new MessageDao();

    public List findAll() {
        return messageDao.findAll();
    }

    public List findByMaxId(int maxId) {
        return messageDao.findByMaxId(maxId);
    }
}

package com.kaishengit.web;

import com.google.gson.Gson;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

public class BaseServlet extends HttpServlet {

    /**
     * 给客户端响应一个JSON数据
     * @param object 要被转成JSON的对象
     * @param response
     * @throws IOException
     */
    public void renderJSON(Object object,HttpServletResponse response) throws IOException {
        String json = new Gson().toJson(object);
        response.setCharacterEncoding("UTF-8");
        response.setContentType("application/json;charset=UTF-8");

        PrintWriter out = response.getWriter();
        out.print(json);
        out.flush();
        out.close();
    }
}

package com.kaishengit.web;

import com.google.gson.Gson;
import com.kaishengit.entity.Message;
import com.kaishengit.service.MessageService;
import org.apache.commons.lang3.StringUtils;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/timeline")
public class TimeLineServlet extends BaseServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String maxId = req.getParameter("maxId");
        int id = 0;
        if(StringUtils.isNumeric(maxId)) {
            id = Integer.parseInt(maxId);
        }


        MessageService messageService = new MessageService();
        List messageList = messageService.findByMaxId(id);
        renderJSON(messageList,resp);
    }
}

# jdbc config  C:\Program Files\Java\jdk1.8.0_101\bin\native2ascii.exe
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql:///db_22
jdbc.username=root
jdbc.password=rootroot

<%@ page contentType="text/html;charset=UTF-8" language="java" %>