目录
26-分类数据展示功能_分析
效果:
分析:
27-分类数据展示功能_实现_后台代码
CategoryDao.java
package cn.itcast.travel.dao;
import cn.itcast.travel.domain.Category;
import java.util.List;
public interface CategoryDao {
/**
* 查询所有
*
* @return
*/
public List<Category> findAll();
}
CategoryDaoImpl.java
package cn.itcast.travel.dao.impl;
import cn.itcast.travel.dao.CategoryDao;
import cn.itcast.travel.domain.Category;
import cn.itcast.travel.util.JDBCUtils;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import java.util.List;
public class CategoryDaoImpl implements CategoryDao {
private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
@Override
public List<Category> findAll() {
String sql = "select * from tab_category";
return template.query(sql, new BeanPropertyRowMapper<Category>(Category.class));
}
}
CategoryService.java
package cn.itcast.travel.service;
import cn.itcast.travel.domain.Category;
import java.util.List;
public interface CategoryService {
public List<Category> findAll();
}
CategoryServlet.java
package cn.itcast.travel.web.servlet;
import cn.itcast.travel.domain.Category;
import cn.itcast.travel.service.CategoryService;
import cn.itcast.travel.service.impl.CategoryServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
@WebServlet("/category/*")
public class CategoryServlet extends BaseServlet {
private CategoryService service = new CategoryServiceImpl();
/**
* 查询所有
*
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
public void findAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.调用service查询所有
List<Category> cs = service.findAll();
//2.序列化json返回
/* ObjectMapper mapper = new ObjectMapper();
response.setContentType("application/json;charset=utf-8");
mapper.writeValue(response.getOutputStream(),cs);*/
writeValue(cs, response);
}
}
在BaseServlet中封装了序列化json的方法
28-分类数据展示功能_实现_前台代码
hader.html加载后,发送ajax请求,请求category/findAll。
29-分类数据展示功能_缓存优化_分析
分析发现,分类的数据在每一次页面加载后 都会重新请求数据库来加载,对数据库的压力比较大,而且分类的数据不会经常产生变化,所以可以使用redis来缓存这个数据。
分析:
30-分类数据展示功能_缓存优化_代码实现
期望 数据中存储的顺序 就是 将来展示的顺序,使用redis的sortedset。
CategoryServiceImpl.java
package cn.itcast.travel.service.impl;
import cn.itcast.travel.dao.CategoryDao;
import cn.itcast.travel.dao.impl.CategoryDaoImpl;
import cn.itcast.travel.domain.Category;
import cn.itcast.travel.service.CategoryService;
import cn.itcast.travel.util.JedisUtil;
import redis.clients.jedis.Jedis;
import redis.clients.jedis.Tuple;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
public class CategoryServiceImpl implements CategoryService {
private CategoryDao categoryDao = new CategoryDaoImpl();
@Override
public List<Category> findAll() {
//1.从redis中查询
//1.1获取jedis客户端
Jedis jedis = JedisUtil.getJedis();
//1.2可使用sortedset排序查询
//Set<String> categorys = jedis.zrange("category", 0, -1);
//1.3查询sortedset中的分数(cid)和值(cname)
Set<Tuple> categorys = jedis.zrangeWithScores("category", 0, -1);
List<Category> cs = null;
//2.判断查询的集合是否为空
if (categorys == null || categorys.size() == 0) {
System.out.println("从数据库查询...");
//3.如果为空,需要从数据库查询,在将数据存入redis
//3.1 从数据库查询
cs = categoryDao.findAll();
//3.2 将集合数据存储到redis中的category的key
for (int i = 0; i < cs.size(); i++) {
jedis.zadd("category", cs.get(i).getCid(), cs.get(i).getCname());
}
} else {
System.out.println("从redis中查询...");
//4.如果不为空,将set的数据存入list
cs = new ArrayList<Category>();
for (Tuple tuple : categorys) {
Category category = new Category();
category.setCname(tuple.getElement());
category.setCid((int) tuple.getScore());
cs.add(category);
}
}
return cs;
}
}