用c标签，el表达式动态取数据库中的值并显示在页面上，动态下拉列表的实现，html:select

heisetoufa

首先jsp头部要引个东西，上次因为没引，找了好半天的错误
<%@ taglib uri="/tags/c" prefix="c" %> 
还有有
<%@ page language="java" pageEncoding="gbk" import="java.util.List,struts.form.KK_BlacklistVehicle_UserEnrolForm"%> 
jsp里写的
<%      List listCode=bean.KK_BlacklistVehicle_UserEnrolSQLBean.getInstance().diffListCode();//从后台把值取出并放在list里    request.setAttribute("listCode", listCode);   %>      <%    //这个是测试这个list在后台有没有取到值    //for(int i = 0; i < listCode.size(); i++) {      //KK_BlacklistVehicle_UserEnrolForm bean = (KK_BlacklistVehicle_UserEnrolForm)listCode.get(i);      //System.out.println("页面上输出的：======="+bean.getKk_BlacklistVehicle_UserEnrol_DW());   //}    %>        <c:if test="${empty listCode}">//这个判断listCode的值有没有传到页面上来，没有的话会在页面上输出not get list value  <%out.print("not get list value"); %> </c:if><html:select property="kk_BlacklistVehicle_UserEnrol_DW" >    <html:option value="">--请选择单位--</html:option>     <c:forEach var="listCode" items="${listCode}">//这句是遍历这个listCode，遍历一次取一次值，赋给 var="listCode"    <html:option value="${listCode.kk_BlacklistVehicle_UserEnrol_DW}">${listCode.kk_BlacklistVehicle_UserEnrol_DW}</html:option>//显示出来遍历后的值     </c:forEach>   </html:select>KK_BlacklistVehicle_UserEnrolSQLBean

public class KK_BlacklistVehicle_UserEnrolSQLBean{ // 声明一个数据库操作对象 PreparedStatement pstmt = null ; // 声明一个结果集对象 ResultSet rs   = null ; // DataBaseConnection为具体的数据库连接及关闭操作类,连接数据库 DataBaseConnection dbc  = new DataBaseConnection() ; //数据库对象 Statement sta   = null ;   private static KK_BlacklistVehicle_UserEnrolSQLBean instance;  public synchronized static KK_BlacklistVehicle_UserEnrolSQLBean getInstance() {  if(instance==null)  {   instance=new KK_BlacklistVehicle_UserEnrolSQLBean();  }  return instance; }  public  List diffListCode( ) {   DataBaseConnection dbc=new DataBaseConnection();   Connection conn=dbc.getConnection();   PreparedStatement pst = null;  List<KK_BlacklistVehicle_UserEnrolForm> list=new ArrayList<KK_BlacklistVehicle_UserEnrolForm>();     String sql="select distinct dw from kk.KKYH ";   try {    pst = conn.prepareStatement(sql);    ResultSet rs=pst.executeQuery();    while(rs.next())    {     KK_BlacklistVehicle_UserEnrolForm userEnrolForm=new KK_BlacklistVehicle_UserEnrolForm();     userEnrolForm.setKk_BlacklistVehicle_UserEnrol_DW(rs.getString(1));     list.add(userEnrolForm);    }   }catch (SQLException e) {    e.printStackTrace();   }finally{    try {     if(pst!=null)     {      pst.close();     }if(conn!=null)     {      conn.close();     }    } catch (Exception e) {    }   }  return list; }} 
  
 
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