redis
这就是redis得一个实例逻辑图。
首先查询redis里面是否有数据，没有，则查询数据库，并且将得到的数据存入到redis中。有，则直接查询redis.
项目的准备
导入相关的资源包
导入相关联的数据库连接工具类和配置
druid.properties
driverClassName=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/day23 username=root password=123456 initialSize=5 maxActive=10 maxWait=3000
jedis.properies
host=127.0.0.1 port=6379 maxTotal=50 maxIdle=10
文件目录
domain包下是实体类
package cn.itcast.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; } }
在web文件夹中有ProvinceServlet ,代码如下：
package cn.itcast.web.servlet; import cn.itcast.domain.Province; import cn.itcast.service.ProvinceService; import cn.itcast.service.impl.ProvinceServiceImp; 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 { //调用service response.setContentType("application/json;charset=utf-8"); ProvinceService service = new ProvinceServiceImp(); //List<Province> list = service.findAll(); String json1 = service.findAllJson(); System.out.println(json1); // ObjectMapper objectMapper = new ObjectMapper(); // String json = objectMapper.writeValueAsString(json1); // System.out.println(json); response.getWriter().write(json1); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request,response); } }
在service包中有ProvinceService接口类和ProvinceServiceImp实现类：
ProvinceService实现类中有两个方法
package cn.itcast.service; import cn.itcast.domain.Province; import java.util.List; public interface ProvinceService { public List<Province> findAll(); public String findAllJson(); }
ProvinceServiceImp实现类：
package cn.itcast.service.impl; import cn.itcast.dao.ProvinceDao; import cn.itcast.dao.impl.ProvinceDaoImp; import cn.itcast.domain.Province; import cn.itcast.jedis.util.JedisPoolUtils; import cn.itcast.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 ProvinceServiceImp implements ProvinceService { private ProvinceDao dao =new ProvinceDaoImp(); @Override public List<Province> findAll() { List<Province> all = dao.findAll(); return all; } @Override public String findAllJson() { //1从redis中查询数据 Jedis jedis = JedisPoolUtils.getJedis(); String province_json = jedis.get("province"); if (province_json==null ||province_json.length()==0) { System.out.println("redis没有数据"); 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有数据"); } return province_json; } }
在dao包中有ProvinceDao和ProvinceDaoImp两个实现类：
provinceDao类
package cn.itcast.dao; import cn.itcast.domain.Province; import java.util.List; public interface ProvinceDao { public List<Province> findAll(); }
ProvinceDaoImp类
package cn.itcast.dao.impl; import cn.itcast.dao.ProvinceDao; import cn.itcast.domain.Province; import cn.itcast.util.JDBCUtils; import org.springframework.jdbc.core.BeanPropertyRowMapper; import org.springframework.jdbc.core.JdbcTemplate; import java.util.List; public class ProvinceDaoImp implements ProvinceDao { //声明成员变量 jdbctemplement //private JdbcTemplate template=new JdbcTemplate(JDBCUtils.getDataSource()); private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource()); @Override public List<Province> findAll() { //1定义sql String sql = "select * from province "; //2执行sal List<Province> list = template.query(sql, new BeanPropertyRowMapper<Province>(Province.class)); return list; } }
前端页面
<!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 () { $.get("provinceServlet",{},function (data) { //1获取select[{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"广州"},{"id":4,"name":"陕西"}] var province = $("#province"); // 2遍历json数组 $(data).each(function () { 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>--请选择省份--</option> </select> </body> </html>
