頁面查詢案例（使用redis數據庫）

時間 2020-06-05

原文原文鏈接

需求：html

1.提供一個index.html頁面，頁面中有個省份，下拉列表
2.當頁面加載完成時，發送ajax請求。加載全部省份java

前期項目初步搭建：jquery

index.htmlgit

$(function(){
	$.get("url",{},funtion(data){
	//url-查詢servlet路徑，{}不要參數，data爲返回的數據，填充到省份列表中
	//由於有查詢數據庫所以有三層架構service(findProvinceServlet)-service(ProvinceService)-dao(ProviniceDao)查詢數據庫
	})
})

ProvinceDaogithub

1.聲明JDBCTemplate，查詢數據庫
2.返回查詢的值(List集合)web

ProvinceServiceajax

1.聲明dao
2.經過Dao返回查詢全部的結果集redis

findProvinceServletspring

1.調用service完成查詢，返回List<Province>
2.將數據返回，由於採用的是Ajax請求，所以須要將數據序列化Json
3.響應sql

總體代碼：

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/jquery-3.3.1.min.js"></script>
    <script>
        $(function () {
            $.get("provinceServlet",{},function (data) {
                var province=$("#province");
                $(data).each(function () {
                    var option="<option name='"+this.id+"'>"+this.name+"</option>";
                    province.append(option);
                });
            });
        });
    </script>
</head>
<body>
    <select id="province">
        <option>---請選擇省份---</option>
    </select>
</body>
</html>

ProvinceDao.java

package cn.stormtides.dao.impl;

import cn.stormtides.dao.ProvinceDao;
import cn.stormtides.domain.Province;
import cn.stormtides.util.JDBCUtils;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

import java.util.List;

public class ProvinceDaoImpl implements ProvinceDao {

    //聲明成員變量
    private JdbcTemplate template=new JdbcTemplate(JDBCUtils.getDataSource());

    @Override
    public List<Province> findAll() {
        String sql="select * from province";

        List<Province> list = template.query(sql, new BeanPropertyRowMapper<>(Province.class));

        return list;
    }
}

ProvinceService.java

package cn.stormtides.service.impl;

import cn.stormtides.dao.ProvinceDao;
import cn.stormtides.dao.impl.ProvinceDaoImpl;
import cn.stormtides.domain.Province;
import cn.stormtides.jedis.util.JedisPoolUtils;
import cn.stormtides.service.ProvinceService;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import redis.clients.jedis.Jedis;

import java.util.List;

public class ProvinceServiceImpl implements ProvinceService {
    //聲明dao
    private ProvinceDao dao=new ProvinceDaoImpl();
    @Override
    public List<Province> findAll() {
        return dao.findAll();
    }

    /**
     * 使用redis緩存
     * @return province_json
     */
    @Override
    public String findAllJson() {
        Jedis jedis= JedisPoolUtils.getJedis();
        String province_json = jedis.get("province");

        if (province_json==null || province_json.length()==0){
            System.out.println("redis沒數據，查詢數據庫");
            List<Province> ps=dao.findAll();
            ObjectMapper mapper=new ObjectMapper();
            try {
                province_json=mapper.writeValueAsString(ps);
            } catch (Exception e) {
                e.printStackTrace();
            }
            jedis.set("province",province_json);
            jedis.close();
        }else {
            System.out.println("redis中有數據");
        }

        return province_json;
    }
}

findProvinceServlet.java

package cn.stormtides.web.servlet;

import cn.stormtides.domain.Province;
import cn.stormtides.service.ProvinceService;
import cn.stormtides.service.impl.ProvinceServiceImpl;
import com.fasterxml.jackson.databind.ObjectMapper;

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

@WebServlet("/provinceServlet")
public class provinceServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //調用service查詢
        ProvinceService service=new ProvinceServiceImpl();

//        //使用普經過程
//        List<Province> list = service.findAll();
//        //序列化list爲json
//        ObjectMapper mapper=new ObjectMapper();
//        String json=mapper.writeValueAsString(list);

        //使用redis緩存
        String json=service.findAllJson();


        System.out.println(json);

        //響應結果
        response.setContentType("application/json;charset=utf-8");
        response.getWriter().write(json);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

完整代碼