936~939 分类数据展示功能,实现前后台代码
分类实现展示功能
效果
后台代码
CategoryDao
public interface CategoryDao { public List<Category> findAll();//查询所有 }
CategoryDaoImpl
public class CategoryDaoImpl implements CategoryDao { private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource()); @Override//查询所有 public List<Category> findAll() { String sql = "select * from tab_category "; return template.query(sql,new BeanPropertyRowMapper<Category>(Category.class)); } }
CategoryService
public interface CategoryService { public List<Category> findAll(); }
CategoryServiceImpl
public class CategoryServiceImpl implements CategoryService { private CategoryDao categoryDao = new CategoryDaoImpl(); @Override public List<Category> findAll() { return categoryDao.findAll(); } }
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; } }
CategoryServlet
@WebServlet("/category/*") public class CategoryServlet extends BaseServlet { private CategoryService service = new CategoryServiceImpl(); //查询所有 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); } }
BaseServlet也可以在UserServlet编写
//直接将传入的对象序列化为json,并且写回客户端 public void writeValue(Object obj, HttpServletResponse response) throws IOException { ObjectMapper mapper = new ObjectMapper(); response.setContentType("application/json;charset=utf-8"); mapper.writeValue(response.getOutputStream(), obj); } //将传入的对象序列化为json,返回 public String writeValueAsString(Object obj) throws JsonProcessingException { ObjectMapper mapper = new ObjectMapper(); return mapper.writeValueAsString(obj); }