Jdis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

创建好三层导入相关的jar包和js

代码实现

sql语句：

CREATE TABLE province(   -- 创建表
    id INT PRIMARY KEY AUTO_INCREMENT,
    NAME VARCHAR(20) NOT NULL
    
);
-- 插入数据
INSERT INTO province VALUES(NULL,'北京');
INSERT INTO province VALUES(NULL,'上海');
INSERT INTO province VALUES(NULL,'广州');
INSERT INTO province VALUES(NULL,'陕西');

SELECT * FROM province;

Province实体类:

package com.itcast.domain;

/**
 * 实体类
 */
public class Province {

    private int id;
    private String name;

    @Override
    public String toString() {
        return "Province{" +
                "id=" + id +
                ", name='" + 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;
    }
}

ProvinceDao接口

package com.itcast.dao;

import com.itcast.domain.Province;

import java.util.List;

/**
 * 业务层
 */
public interface ProvinceDao {

    /**
     * 查询所有
     */
    public List<Province> findAll();

}

ProvinceDaoImpl实体类

package com.itcast.dao.impl;

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

import java.util.List;

public class ProvinceDaoImpl implements ProvinceDao {

    //1. 声明一个成员变量 jdbctemplement
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());



    @Override
    public List<Province> findAll() {
        //1. 定义sql语句
        String sql = "SELECT * FROM province";
        //2. 执行sql
        List<Province> query = template.query(sql, new BeanPropertyRowMapper<Province>(Province.class));

        return query;
    }
}

ProvinceService接口

package com.itcast.service;

import com.itcast.domain.Province;

import java.util.List;

/**
 *  业务
 */
public interface ProvinceService {

    /**
     * 查询所有
     * @return
     */
    public List<Province> findAll();
}

ProvinceServiceImpl实体类

package com.itcast.service.impl;

import com.itcast.dao.ProvinceDao;
import com.itcast.dao.impl.ProvinceDaoImpl;
import com.itcast.domain.Province;
import com.itcast.service.ProvinceService;

import java.util.List;

public class ProvinceServiceImpl implements ProvinceService {

    //1. 声明dao
    private ProvinceDao dao = new ProvinceDaoImpl();

    @Override
    public List<Province> findAll() {
        //通过dao返回查询所有结果
        return dao.findAll();
    }
}

JDBCUtils工具类

package com.itcast.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();
    }
}

ProvinceServlet类

package com.itcast.web.servlet;

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

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;

/**
 *  web层
 */
@WebServlet(name = "provinceServlet", value = "/provinceServlet")
public class ProvinceServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) 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);

        System.out.println(json);

        //3.响应结果
        resp.setContentType("application/json;charset=utf-8");// 设置编码格式
        //写出
        resp.getWriter().write(json);


    }
}

index.html页面：

<!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方法追加option
                    province.append(option);

                });


            })


        });
    </script>
</head>
<body>


<select id="province">
    <option>--请选择省份--</option>


</select>

</body>
</html>

redis缓存优化

ProvinceService接口

public interface ProvinceService {

    /**
     * 查询所有
     * @return
     */
    public List<Province> findAll();

    /**
     * redis缓存优化
     * @return
     */
    public String findAllJson();
}

ProvinceServiceImpl实体类

    /**
     *  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 数据是否为null
        if (province_json == null || province_json.length() == 0){
            //redis中没有数据
            System.out.println("redis中没有数据，查询数据库...");
            //2.1从数据库查询
            List<Province> list = dao.findAll();
            //2.2将list序列化json
            ObjectMapper modules = new ObjectMapper();
            try {
                province_json = modules.writeValueAsString(list);
            } catch (JsonProcessingException e) {
                e.printStackTrace();
            }

            //2.3 将json数据存入redis中
            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类

package com.itcast.web.servlet;

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

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;

/**
 *  web层
 */
@WebServlet(name = "provinceServlet", value = "/provinceServlet")
public class ProvinceServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) 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);
        */
        //1. 调用service查询
        ProvinceService service = new ProvinceServiceImpl();
        String json = service.findAllJson();

        System.out.println(json);

        //3.响应结果
        resp.setContentType("application/json;charset=utf-8");// 设置编码格式
        //写出
        resp.getWriter().write(json);


    }
}