redis.maxIdle=30
redis.minIdle=10
redis.maxTotal=100
redis.url=192.168.1.55
redis.port=6379

package www.test.utils;

import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

public class JedisPoolUtils {

    private static JedisPool pool = null;

    static {

        //加载配置文件
        InputStream in = JedisPoolUtils.class.getClassLoader().getResourceAsStream("redis.properties");
        Properties pro = new Properties();
        try {
            pro.load(in);
        } catch (IOException e) {
            e.printStackTrace();
        }

        //获得池子对象
        JedisPoolConfig poolConfig = new JedisPoolConfig();
        poolConfig.setMaxIdle(Integer.parseInt(pro.get("redis.maxIdle").toString()));//最大闲置个数
        poolConfig.setMinIdle(Integer.parseInt(pro.get("redis.minIdle").toString()));//最小闲置个数
        poolConfig.setMaxTotal(Integer.parseInt(pro.get("redis.maxTotal").toString()));//最大连接数
        pool = new JedisPool(poolConfig, pro.getProperty("redis.url"),
                Integer.parseInt(pro.get("redis.port").toString()));
    }

    //获得jedis资源的方法
    public static Jedis getJedis() {
        return pool.getResource();
    }

}

package www.test.web.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gson.Gson;

import redis.clients.jedis.Jedis;
import www.test.domain.Category;
import www.test.service.ProductService;
import www.test.utils.JedisPoolUtils;

public class CategoryListServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        ProductService service = new ProductService();

        //先从缓存中查询categoryList 如果有直接使用 没有再才从数据库中查询  查询获得之后存到缓存中
        //1、获得jedis对象 连接redis数据库
        Jedis jedis = JedisPoolUtils.getJedis();
        String categoryListJson = jedis.get("categoryListJson");
        
        //2、判断categoryListJson是否为空
        if(categoryListJson==null){
            System.out.println("缓存没有数据 查询数据库");
            
            // 准备分类数据
            List<Category> categoryList = null;
            try {
                categoryList = service.findAllCategory();
            } catch (SQLException e) {
                
                e.printStackTrace();
            }
            //使用转换工具将categoryList转换成json格式
            Gson gson = new Gson();
            categoryListJson = gson.toJson(categoryList);
            //将从数据库中获得的categoryListJson存储到缓存中
            jedis.set("categoryListJson", categoryListJson);
        }
        
        //将转换后的json格式字符串写出
         //写出前先解决乱码问题
        response.setContentType("text/html;charset=UTF-8");
        response.getWriter().write(categoryListJson);
    }

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

}