使用Ajax和Jquery配合数据库实现下拉框的二级联动的示例

站长资源 2024/11/27 佚名

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首先我们需要先建立好数据库，将一些数据插入进去

需要两张表：

province：省份表

city：城市表

如图：

然后再在java中建立相关的实体类与之对应

再然后，我们就能开始做jdbc的操作了

public class ConnectionFactory { 
 private static String driver; 
 private static String url; 
 private static String user; 
 private static String password; 
 static { 
  Properties prop = new Properties(); 
  //读取文件 
   
  try { 
   InputStream in = ConnectionFactory.class.getResourceAsStream("./jdbc.properties"); 
    
   prop.load(in); 
   driver = prop.getProperty("jdbc.driver"); 
   url = prop.getProperty("jdbc.url"); 
   user = prop.getProperty("jdbc.user"); 
   password = prop.getProperty("jdbc.password"); 
  } catch (IOException e) { 
   e.printStackTrace(); 
  } 
   
 } 
  
 /** 
  * 获取连接对象 
  * @return 
  */ 
 public static Connection getConnection(){ 
  Connection conn = null; 
   
  try { 
   Class.forName(driver); 
   conn = DriverManager.getConnection(url, user, password); 
    
  } catch (Exception e) { 
   throw new RuntimeException(e); 
  } 
   
  return conn; 
 } 
  
 /** 
  * 关闭资源 
  * @param conn 
  * @param pstmt 
  * @param stmt 
  * @param rs 
  */ 
 public static void close(Connection conn,PreparedStatement pstmt,Statement stmt,ResultSet rs){ 
    
   try { 
    if (conn != null) { 
     conn.close(); 
    } 
     
    if (pstmt != null) { 
     pstmt.close(); 
    } 
     
    if (stmt != null) { 
     stmt.close(); 
    } 
     
    if (rs != null) { 
     rs.close(); 
    } 
   } catch (SQLException e) { 
    throw new RuntimeException(e); 
   } 
   
 }

首先我们可以在页面加载的时候获取所有省份的信息，SQL语句如下

Connection conn = null; 
 PreparedStatement pstmt = null; 
 Province province2 = null; 
  
 @Override 
 public ArrayList<Province> findAllPro() { 
  ResultSet rs = null; 
  ArrayList<Province> pros = null; 
  try { 
   String sql = "select id,place from province"; 
   conn = ConnectionFactory.getConnection(); 
   pstmt = conn.prepareStatement(sql); 
   pros = new ArrayList<Province>(); 
    
   rs = pstmt.executeQuery(); 
    
   while(rs.next()){ 
    Province province = new Province(); 
    province.setId(rs.getInt(1)); 
    province.setPlace(rs.getString(2)); 
    pros.add(province); 
   } 
    
  } catch (SQLException e) { 
   throw new RuntimeException(e); 
  } 
   
  return pros; 
 }

将查到的数据放到后台,建立一个SelectedServlet类，用于接收查询到的所有省份的信息

response.setContentType("application/json;charset=utf-8"); 
  response.setCharacterEncoding("utf-8"); 
  request.setCharacterEncoding("utf-8"); 
  //创建一个Place对象 
  ArrayList<Province> pros= new Place().findAllPro(); 
  PrintWriter out = response.getWriter(); 
  //将集合直接转换为Json对象 
  out.write(JSONArray.fromObject(pros).toString());

在这里会用到集合转换Json对象，我们需要导入以下几个包

然后我们开始写前台页面：

<body> 
  省份:<select id="province"> 
   <option>--请选择省份--</option> 
  </select> 
   
  城市:<select id="city"> 
    <option>--请选择城市--</option> 
   </select> 
  <br/><br/> 
  <span></span> 
 </body>

然后jQuery代码如下:（由于我导入的jQuery版本比较低，所以使用的方法是getJSON，而不是getJson）

$.getJSON("SelectedServlet",function(data,textStatus){ 
 var provinces = data; 
      
 var res = ""; 
 for(var i =0;i<provinces.length;i++){ 
 <span style="white-space:pre"> </span>res += "<option>"+provinces[i].place+"</option>"; 
 } 
  $("#province").append(res); 
 });

这样就能在页面加载的时候获取到数据

然后我们再来做联动，首先给下拉框添加一个change事件，然后获取选中的信息，将选中的信息发送到另一个CityServlet中

//下拉框改变时触发的事件 
 $("#province").change(function(){ 
 var seled = $("option:selected").html(); 
      
 $("span").html(seled); 
 $.getJSON("CityServlet",{ 
  "province":encodeURI(encodeURI(seled)) 
     },function(data){ 
  $("#city").html(""); 
  var citys = data; 
  var res = ""; 
  for(var i = 0;i<citys.length;i++){ 
   res += "<option>"+citys[i].place+"</option>"; 
  } 
  $("#city").append(res); 
 }); 
      
 });

服务器通过获得的信息通过sql语句查询出来，SQL代码如下：

public ArrayList<City> findAllCityByPro(String name) { 
  ResultSet rs = null; 
  ArrayList<City> citys = null; 
  try { 
   //通过名字获得所有值 
   String sql = "select c.city_place from city c ," 
     + "province p where c.province_id = " 
     + " (select id from province where place = '"+ name +"') " 
     + " and c.province_id = p.id"; 
   conn = ConnectionFactory.getConnection(); 
   pstmt = conn.prepareStatement(sql); 
   citys = new ArrayList<City>(); 
   System.out.println(sql); 
   rs = pstmt.executeQuery(); 
    
   while(rs.next()){ 
    City city = new City(); 
    city.setPlace(rs.getString(1)); 
    citys.add(city); 
   } 
   System.out.println(citys); 
    
  } catch (SQLException e) { 
   e.printStackTrace(); 
  } 
   
  return citys; 
 }

将查询到的数据发送到后台，后台接收到数据后将其转换为Json对象，并通过回调函数发送到前台，然后前台就可以通过事件直接获取到数据，而不用各种跳转页面，这就是Ajax(Asynchronous Javascript And XML),

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
   throws ServletException, IOException { 
  response.setContentType("application/json;charset=utf-8"); 
  response.setCharacterEncoding("utf-8"); 
  request.setCharacterEncoding("utf-8"); 
//  String proName = "浙江"; 
  String proName = URLDecoder.decode(URLDecoder.decode(request.getParameter("province"), "utf-8"), 
    "utf-8"); 
  ArrayList<City> citys= new Place().findAllCityByPro(proName); 
  PrintWriter out = response.getWriter(); 
  out.write(JSONArray.fromObject(citys).toString()); 
   
 }

至于显示页面的代码也在前面写到jQuery语句中了

效果如下：