案例
需求:
- 提供index.html页面 页面中有一个省份 下拉列表
- 当页面加载完成后 发送ajax请求 加载所有省份
java代码实现
配置文件
数据库配置文件:druid.properties
driverClassName=com.mysql.jdbc.Driver url=jdbc:mysql:///day23 username=root password=root initialSize=5 maxActive=10 maxWait=3000
实体类
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; } }
ProvinceDao接口
public interface ProvinceDao { public List<Province> findAll(); }
ProvinceDaoImpl类
public class ProvinceDaoImpl implements ProvinceDao { //1.声明成员变量 jdbctemplement private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource()); @Override public List<Province> findAll() { //1.定义sql String sql = "select * from province "; //2.执行sql List<Province> list = template.query(sql, new BeanPropertyRowMapper<Province>(Province.class)); return list; } }
ProvinceService接口
public interface ProvinceService { public List<Province> findAll(); public String findAllJson(); }
ProvinceServiceImpl类
public class ProvinceServiceImpl implements ProvinceService { //声明dao private ProvinceDao dao = new ProvinceDaoImpl(); @Override public List<Province> findAll() { return dao.findAll(); } /** 使用redis缓存 */ @Override public String findAllJson() { //1.先从redis中查询数据 //1.1获取redis客户端连接 Jedis jedis = JedisPoolUtils.getJedis(); String province_json = jedis.get("province"); //2判断 province_json 数据是否为null if(province_json == null || province_json.length() == 0){ //redis中没有数据 System.out.println("redis中没数据,查询数据库..."); //2.1从数据中查询 List<Province> ps = dao.findAll(); //2.2将list序列化为json ObjectMapper mapper = new ObjectMapper(); try { province_json = mapper.writeValueAsString(ps); } catch (JsonProcessingException e) { e.printStackTrace(); } //2.3 将json数据存入redis jedis.set("province",province_json); //归还连接 jedis.close(); }else{ System.out.println("redis中有数据,查询缓存..."); } return province_json; } }
工具类:JDBCUtils
public class JDBCUtils { private static DataSource ds ; static { try { //1.加载配置文件 Properties pro = new Properties(); //使用ClassLoader加载配置文件,获取字节输入流 InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties"); pro.load(is); //2.初始化连接池对象 ds = DruidDataSourceFactory.createDataSource(pro); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } } /** * 获取连接池对象 */ public static DataSource getDataSource(){ return ds; } /** * 获取连接Connection对象 */ public static Connection getConnection() throws SQLException { return ds.getConnection(); } }
ProvinceServlet类
@WebServlet("/provinceServlet") public class ProvinceServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* //1.调用service查询 ProvinceService service = new ProvinceServiceImpl(); List<Province> list = service.findAll(); //2.序列化list为json ObjectMapper mapper = new ObjectMapper(); String json = mapper.writeValueAsString(list);*/ //1.调用service查询 ProvinceService service = new ProvinceServiceImpl(); String json = service.findAllJson(); System.out.println(json); //3.响应结果 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 () { //发送ajax请求,加载所有省份数据 $.get("provinceServlet",{},function (data) { //[{"id":1,"name":"北京"},{"id":2,"name":"上海"},{"id":3,"name":"广州"},{"id":4,"name":"陕西"}] //1.获取select var province = $("#province"); //2.遍历json数组 $(data).each(function () { //3.创建<option> 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>标签:province,String,id,案例,json,public,name From: https://www.cnblogs.com/aimz01/p/16613857.html