JavaWeb黑马旅游网-学习笔记05【分类数据展示功能】

亦凉 2022-11-04 08:06 116阅读 0赞

>  *  **[Java后端 学习路线 笔记汇总表【黑马程序员】][Java_ _]**
> 
> 1.  [JavaWeb黑马旅游网-学习笔记01【准备工作】][JavaWeb_-_01]
> 2.  [JavaWeb黑马旅游网-学习笔记02【注册功能】][JavaWeb_-_02]
> 3.  [JavaWeb黑马旅游网-学习笔记03【登陆和退出功能】][JavaWeb_-_03]
> 4.  [JavaWeb黑马旅游网-学习笔记04【BaseServlet抽取】][JavaWeb_-_04_BaseServlet]
> 5.  [JavaWeb黑马旅游网-学习笔记05【分类数据展示功能】][JavaWeb_-_05]
> 6.  [JavaWeb黑马旅游网-学习笔记06【旅游线路分页展示分页展示】][JavaWeb_-_06]
> 7.  [JavaWeb黑马旅游网-学习笔记07【旅游线路查询】][JavaWeb_-_07]
> 8.  [JavaWeb黑马旅游网-学习笔记08【旅游线路详情】][JavaWeb_-_08]
> 9.  [JavaWeb黑马旅游网-学习笔记09【旅游线路收藏】][JavaWeb_-_09]
> 10. [JavaWeb黑马旅游网-学习笔记10【项目代码】][JavaWeb_-_10]

**目录**

26-分类数据展示功能\_分析

27-分类数据展示功能\_实现\_后台代码

CategoryDao.java

CategoryDaoImpl.java

CategoryService.java

CategoryServlet.java

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

29-分类数据展示功能\_缓存优化\_分析

30-分类数据展示功能\_缓存优化\_代码实现

CategoryServiceImpl.java

--------------------

# 26-分类数据展示功能\_分析 #

> **效果：**
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70][]
> 
> ![20210301212654779.png][]

> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 1][]

> **分析：**
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 2][]

# 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 ##

> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 3][]

# 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。
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 4][]
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 5][]

> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 6][]

# 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：
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 7][]

# 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。
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 8][]

## 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;
        }
    }

> ![20210302133343145.png][]
> 
> ![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDk0OTEzNQ_size_16_color_FFFFFF_t_70 9][]

[Java_ _]: https://blog.csdn.net/weixin_44949135/article/details/113773297
[JavaWeb_-_01]: https://blog.csdn.net/weixin_44949135/article/details/114031199
[JavaWeb_-_02]: https://blog.csdn.net/weixin_44949135/article/details/114121075
[JavaWeb_-_03]: https://blog.csdn.net/weixin_44949135/article/details/114229387
[JavaWeb_-_04_BaseServlet]: https://blog.csdn.net/weixin_44949135/article/details/114259853
[JavaWeb_-_05]: https://blog.csdn.net/weixin_44949135/article/details/114272117
[JavaWeb_-_06]: https://blog.csdn.net/weixin_44949135/article/details/114283166
[JavaWeb_-_07]: https://blog.csdn.net/weixin_44949135/article/details/114288829
[JavaWeb_-_08]: https://blog.csdn.net/weixin_44949135/article/details/114291075
[JavaWeb_-_09]: https://blog.csdn.net/weixin_44949135/article/details/114293637
[JavaWeb_-_10]: https://blog.csdn.net/weixin_44949135/article/details/114305933
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