Redis_案例_hehe.employment.over.23.6

23.9 Redis_案例

23.9.1 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。
 - ***notes***：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。
 - ***图示：***

23.9.2 示例

Province

package com.xww.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;
    }
}

JDBCUtils

package com.xww.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();
    }
}

JedisPoolUtils

package com.xww.jedis.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();
    }
}

ProvinceDao

package com.xww.dao;

import com.xww.domain.Province;

import java.util.List;

public interface ProvinceDao {
    
    
    public List<Province> findAll();
}

ProvinceDaoImpl

package com.xww.dao.impl;

import com.xww.dao.ProvinceDao;
import com.xww.domain.Province;
import com.xww.util.JDBCUtils;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

import java.util.List;

public class ProvinceDaoImpl implements ProvinceDao{
    
    
    //1.声明成员变量 jdbctemplement
    private JdbcTemplate template = 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 = template.query(sql, new BeanPropertyRowMapper<Province>(Province.class));
        return list;
    }
}

ProvinceService

package com.xww.service;

import com.xww.domain.Province;

import java.util.List;

public interface ProvinceService {
    
    

    public List<Province> findAll();
    public String findAllJson();
}

ProvinceServiceImpl

package com.xww.service.impl;

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

import java.util.List;

public class ProvinceServiceImpl implements ProvinceService {
    
    
    //声明dao
    private ProvinceDao dao = new ProvinceDaoImpl();

    @Override
    public List<Province> findAll() {
    
    
        return dao.findAll();
    }

    /**
     使用redis缓存
     */
    @Override
    public String findAllJson() {
    
    
        //1.先从redis中查询数据
        //1.1获取redis客户端连接
        Jedis jedis = JedisPoolUtils.getJedis();
        String province_json = jedis.get("province");

        //2判断 province_json 数据是否为null
        if(province_json == null || province_json.length() == 0){
    
    
            //redis中没有数据
            System.out.println("redis中没数据，查询数据库...");
            //2.1从数据中查询
            List<Province> ps = dao.findAll();
            //2.2将list序列化为json
            ObjectMapper mapper = new ObjectMapper();
            try {
    
    
                province_json = mapper.writeValueAsString(ps);
            } catch (JsonProcessingException e) {
    
    
                e.printStackTrace();
            }
            //2.3 将json数据存入redis
            jedis.set("province",province_json);
            //归还连接
            jedis.close();
        }else{
    
    
            System.out.println("redis中有数据，查询缓存...");
        }
        return province_json;
    }
}

ProvinceServlet

package com.xww.web.servlet;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.xww.domain.Province;
import com.xww.service.ProvinceService;
import com.xww.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;
import java.util.List;

@WebServlet("/provinceServlet")
public class ProvinceServlet extends HttpServlet {
    
    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    
    
        //redis缓存
        //1.调用service查询
        ProvinceService service = new ProvinceServiceImpl();
        String json = service.findAllJson();
        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);
    }
}

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 () {
     
     
            //发送ajax请求，加载所有省份数据
            $.get("provinceServlet",{
     
     },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
                var province = $("#province");
                //2.遍历json数组
                $(data).each(function () {
     
     
                    //3.创建<option>
                    var option = "<option name='"+this.id+"'>"+this.name+"</option>";

                    //4.调用select的append追加option
                    province.append(option);
                });
            });
        });
    </script>
    
</head>
<body>
        <select id="province">
            <option>--请选择省份--</option>
        </select>
</body>
</html>