Redis案例 February 3，2020

## 案例：
案例需求：
　　1. 提供index.html页面，页面中有一个省份 下拉列表
　　2. 当 页面加载完成后 发送ajax请求，加载所有省份

　　* 注意：使用redis缓存一些不经常发生变化的数据。
　　　　* 数据库的数据一旦发生改变，则需要更新缓存。
　　　　* 数据库的表执行 增删改的相关操作，需要将redis缓存数据情况，再次存入
　　　　* 在service对应的增删改方法中，将redis数据删除。

 

分析：

 

 

 

代码结构：

 

 

 

代码：

dao

 

package dao;import domain.Province;import java.util.List;public interface ProvinceDao {    //查询所有    public List<Province> findAll();}

 

 

package dao.impl;import dao.ProvinceDao;import domain.Province;import org.springframework.jdbc.core.BeanPropertyRowMapper;import org.springframework.jdbc.core.JdbcTemplate;import util.JDBCUtils;import java.util.List;public class ProvinceDaoImpl implements ProvinceDao {    //1.声明成员变量 JdbcTemplate    private JdbcTemplate jdbcTemplate = new JdbcTemplate(JDBCUtils.getDataSource());    @Override    public List<Province> findAll() {        //1.定义sql        String sql = "select * from province";        //2.执行sql        List<Province> list = jdbcTemplate.query(sql, new BeanPropertyRowMapper<Province>(Province.class));        return list;    }}

 

domain

 

package domain;public class Province {    private int id;    private String name;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    @Override    public String toString() {        return "Province{"                  "id="   id                  ", name='"   name   '\''                  '}';    }}

 

service

 

package service;import domain.Province;import java.util.List;public interface ProvinceService {    //查询所有    public List<Province> findAll();    public String finAllJson();}

 

 

package service.impl;import com.fasterxml.jackson.core.JsonProcessingException;import com.fasterxml.jackson.databind.ObjectMapper;import dao.ProvinceDao;import dao.impl.ProvinceDaoImpl;import domain.Province;import redis.clients.jedis.Jedis;import service.ProvinceService;import util.JedisPoolUtils;import java.util.List;public class ProvinceServiceImpl implements ProvinceService {    private ProvinceDao provinceDao = new ProvinceDaoImpl();    @Override    public List<Province> findAll() {        return provinceDao.findAll();    }    /**     * 使用redis缓存     * @return     */    @Override    public String finAllJson() {        //1.先从redis中查询数据        //1.1获取redis客户端连接        Jedis jedis = JedisPoolUtils.getJedis();        String redis_json = jedis.get("province");        //2判断 redis_json 数据是否为null        if(redis_json ==null || redis_json.length() == 0){            //redis中没有缓存            System.out.println("redis中不存在缓存，从数据库查询");            //2.1从数据库查询            List<Province> list = provinceDao.findAll();            //2.2将list序列化为json            ObjectMapper objectMapper = new ObjectMapper();            try {                redis_json = objectMapper.writeValueAsString(list);            } catch (JsonProcessingException e) {                e.printStackTrace();            }            //2.3 将json数据存入redis            jedis.set("province",redis_json);            //归还连接            jedis.close();        }else {            System.out.println("redis存在缓存");        }        return redis_json;    }}

 

util

 

package util;import com.alibaba.druid.pool.DruidDataSourceFactory;import javax.sql.DataSource;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.SQLException;import java.util.Properties;/** * JDBC工具类 使用Durid连接池 */public class JDBCUtils {    private static DataSource ds ;    static {        try {            //1.加载配置文件            Properties pro = new Properties();            //使用ClassLoader加载配置文件，获取字节输入流            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");            pro.load(is);            //2.初始化连接池对象            ds = DruidDataSourceFactory.createDataSource(pro);        } catch (IOException e) {            e.printStackTrace();        } catch (Exception e) {            e.printStackTrace();        }    }    /**     * 获取连接池对象     */    public static DataSource getDataSource(){        return ds;    }    /**     * 获取连接Connection对象     */    public static Connection getConnection() throws SQLException {        return  ds.getConnection();    }}

 

 

package util;import redis.clients.jedis.Jedis;import redis.clients.jedis.JedisPool;import redis.clients.jedis.JedisPoolConfig;import java.io.IOException;import java.io.InputStream;import java.util.Properties;/** JedisPool工具类 加载配置文件，配置连接池的参数 提供获取连接的方法 */public class JedisPoolUtils {    private static JedisPool jedisPool;    static{        //读取配置文件        InputStream is = JedisPoolUtils.class.getClassLoader().getResourceAsStream("jedis.properties");        //创建Properties对象        Properties pro = new Properties();        //关联文件        try {            pro.load(is);        } catch (IOException e) {            e.printStackTrace();        }        //获取数据，设置到JedisPoolConfig中        JedisPoolConfig config = new JedisPoolConfig();        config.setMaxTotal(Integer.parseInt(pro.getProperty("maxTotal")));        config.setMaxIdle(Integer.parseInt(pro.getProperty("maxIdle")));        //初始化JedisPool        jedisPool = new JedisPool(config,pro.getProperty("host"),Integer.parseInt(pro.getProperty("port")));    }    /**     * 获取连接方法     */    public static Jedis getJedis(){        return jedisPool.getResource();    }}

 

 

 

 

web

 

package web.servlet;import service.ProvinceService;import service.impl.ProvinceServiceImpl;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;@WebServlet("/findProvinceServlet")public class FindProvinceServlet extends HttpServlet {    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//         //1.调用service查询//        ProvinceService provinceService = new ProvinceServiceImpl();//        List<Province> list = provinceService.findAll();//        //2.序列化list为json//        ObjectMapper objectMapper = new ObjectMapper();//        String json = objectMapper.writeValueAsString(list);        //1.调用service查询       ProvinceService provinceService = new ProvinceServiceImpl();        String json = provinceService.finAllJson();        System.out.println(json);        //3.响应结果        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);    }}

 

 

 

<!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 () {           //发送ajax请求，获取所有省份信息            $.get("findProvinceServlet",{},function (data) {                //[{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"广州"},{"id":4,"name":"陕西"}]                //1.获取select的id                var province = $("#province");                //2.遍历json数组                //  for (var i = 0; i < data.length; i  ) {                //      var opption = "<option name='" data[i].id "'>" data[i].name "</option>"                //      province.append(opption);                //  }                $(data).each(function () {                    //3.创建option标签                    var opption = "<option name='" this.id "'>" this.name "</option>"                    //4.调用select的append追加option                    province.append(opption);                });           });        });    </script></head><body>    <select id="province">        <option>--请选择省份-- </option>    </select></body></html>

 

来源：https://www.icode9.com/content-2-630301.html