**
1前期准备
1建立一个web项目
2打开数据库
3打开redis服务器
**
建立web项目如下
建立如下文件包
2详细的文件内如下
导入下述的lib文件
这些资源包可以从百度云盘获取
链接：https://pan.baidu.com/s/16FwmfIZ9Zw7B-dG_GZ6bcA
提取码：9dp3
1）首先是在dao文件下建立一个ProvinceDao的接口和ProvinceDaoImp实现类，具体代码如下；
public interface ProvinceDao { public List<Province> findAll(); } `` ```java 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; } }
在domain下做一个province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; } }
service包如下：
public interface ProvinceService { public List<Province> findAll(); public String findAllJson(); } `` ```java 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; } }
util包是两个工具类；JDBCUtils和JedisPoolUtils
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(); } }
public class JedisPoolUtils { private static JedisPool jedisPool; static{ //读取配置文件 InputStream is = JedisPoolUtils.class.getClassLoader().getResourceAsStream("jedis.properties"); //创建Properties对象 Properties pro = new Properties(); //关联文件 try { pro.load(is); } catch (IOException e) { e.printStackTrace(); } //获取数据，设置到JedisPoolConfig中 JedisPoolConfig config = new JedisPoolConfig(); config.setMaxTotal(Integer.parseInt(pro.getProperty("maxTotal"))); config.setMaxIdle(Integer.parseInt(pro.getProperty("maxIdle"))); //初始化JedisPool jedisPool = new JedisPool(config,pro.getProperty("host"),Integer.parseInt(pro.getProperty("port"))); } /** * 获取连接方法 */ public static Jedis getJedis(){ return jedisPool.getResource(); } }
在web文件下建立一个servlet文件夹，存放ProvinceServlet类
@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); } }
最后还有两个配置文件druid.properties和jedies.properties;
driverClassName=com.mysql.jdbc.Driver url=jdbc:mysql://localhost:3306/day23 username=root password=123456 initialSize=5 maxActive=10 maxWait=3000
host=127.0.0.1 port=6379 maxTotal=50 maxIdle=10 `` `剩下就是index.htmll ```javascript <!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>
按照上述步骤操作，一个小的案例就可以使用了。
