1. 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) {
                //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>--选择省份--</option>

    </select>
</body>
</html>

2. Profiles

2.1 druid.properties

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///test
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000

2.2 jedis.properties

#最大活动对象数     
maxTotal=1000    
#最大能够保持idel状态的对象数      
maxIdle=100  
#最小能够保持idel状态的对象数   
minIdle=50    
#当池内没有返回对象时，最大等待时间    
maxWaitMillis=10000    
#当调用borrow Object方法时，是否进行有效性检查    
testOnBorrow=true    
#当调用return Object方法时，是否进行有效性检查    
testOnReturn=true  
#“空闲链接”检测线程，检测的周期，毫秒数。如果为负值，表示不运行“检测线程”。默认为-1.  
timeBetweenEvictionRunsMillis=30000  
#向调用者输出“链接”对象时，是否检测它的空闲超时；  
testWhileIdle=true  
# 对于“空闲链接”检测线程而言，每次检测的链接资源的个数。默认为3.  
numTestsPerEvictionRun=50  
#redis服务器的IP    
host=127.0.0.1
#redis服务器的Port    
port=6379

3. Java file

3.1 ProvinceDaoImpl.java

package cn.siyi.dao.impl;

import cn.siyi.dao.ProvinceDao;
import cn.siyi.domain.Province;
import cn.siyi.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语句
        List<Province> list = template.query(sql, new BeanPropertyRowMapper<Province>(Province.class));
        return list;
    }
}

3.2 Province.java

package cn.siyi.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 + '\'' +
                '}';
    }
}

3.3 JedisPoolUtils.java

package cn.siyi.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;

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.setMaxTotal(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();
    }
}

3.4 ProvinceServiceImpl.java

package cn.siyi.service.impl;

import cn.siyi.dao.ProvinceDao;
import cn.siyi.dao.impl.ProvinceDaoImpl;
import cn.siyi.domain.Province;
import cn.siyi.jedis.util.JedisPoolUtils;
import cn.siyi.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 {

    //声明dao
    private ProvinceDao dao = new ProvinceDaoImpl();

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

    /**
     * 使用redis缓存
     * @return
     */
    @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中没有，查询DB");
            //2.1从数据库中查询
            List<Province> ps = dao.findAll();
            //2.2将list序列化为json
            ObjectMapper objectMapper = new ObjectMapper();
            try {
                province_json = objectMapper.writeValueAsString(ps);
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }
            //2.3将json数据存入redis中
            jedis.set("province",province_json);
        }else{
            System.out.println("redis中有数据");
        }
        jedis.close();
        return province_json;
    }
}

3.5 JDBCUtils.java

package cn.siyi.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();
    }
}

3.6 ProvinceServlet.java

package cn.siyi.web.servlet;

import cn.siyi.domain.Province;
import cn.siyi.service.ProvinceService;
import cn.siyi.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 {
        /*//1.调用service查询
        ProvinceService service = new ProvinceServiceImpl();
        List<Province> list = service.findAll();
        //2.序列化list为json
        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(list);*/

        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);
    }
}