Redis案例 February 3，2020
作者：互联网
## 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>
标签：February,java,name,redis,Redis,json,2020,import,public 来源： https://www.cnblogs.com/yyanghang/p/12255449.html