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;
public class JDBCUtils {
private static DataSource ds ;
static {
try {
Properties pro = new Properties();
InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
pro.load(is);
ds = DruidDataSourceFactory.createDataSource(pro);
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
public static DataSource getDataSource(){
return ds;
}
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;
public class JedisPoolUtils {
private static JedisPool jedisPool;
static{
InputStream is = JedisPoolUtils.class.getClassLoader().getResourceAsStream("jedis.properties");
Properties pro = new Properties();
try {
pro.load(is);
} catch (IOException e) {
e.printStackTrace();
}
JedisPoolConfig config = new JedisPoolConfig();
config.setMaxTotal(Integer.parseInt(pro.getProperty("maxTotal")));
config.setMaxIdle(Integer.parseInt(pro.getProperty("maxIdle")));
jedisPool = new JedisPool(config,pro.getProperty("host"),Integer.parseInt(pro.getProperty("port")));
}
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{
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
@Override
public List<Province> findAll() {
String sql = "select * from province ";
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 {
private ProvinceDao dao = new ProvinceDaoImpl();
@Override
public List<Province> findAll() {
return dao.findAll();
}
@Override
public String findAllJson() {
Jedis jedis = JedisPoolUtils.getJedis();
String province_json = jedis.get("province");
if(province_json == null || province_json.length() == 0){
System.out.println("redis中没数据,查询数据库...");
List<Province> ps = dao.findAll();
ObjectMapper mapper = new ObjectMapper();
try {
province_json = mapper.writeValueAsString(ps);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
jedis.set("province",province_json);
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 {
ProvinceService service = new ProvinceServiceImpl();
String json = service.findAllJson();
System.out.println(json);
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 () {
$.get("provinceServlet",{
},function (data) {
var province = $("#province");
$(data).each(function () {
var option = "<option name='"+this.id+"'>"+this.name+"</option>";
province.append(option);
});
});
});
</script>
</head>
<body>
<select id="province">
<option>--请选择省份--</option>
</select>
</body>
</html>