用jq和ajax实现

1.在jsp页面上

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

$(function(){
        $.get("productType1_findAll.action",function(data){    -------->从自己的action中查询，返回productTypeList
            $.each(data.productTypeList,function(i,element){
                var productId=‘${productId}‘;
                if(productId==element.id){
                    $("#productId").append("<option value=http://www.mamicode.com/‘"+element.id+"‘selected>"+element.productTypeName+"</option>");
                }else{
                    $("#productId").append("<option value=http://www.mamicode.com/‘"+element.id+"‘ >"+element.productTypeName+"</option>");
                }                
            })
        },"json")
    })

------------------------------------------------------------------------------------------------------------------------------------

<div class="field">
            <select name="productId" id="productId" class="input w50">
              <option value="">请选择</option>   
            </select>
            <div class="tips"></div>
          </div>

下拉框获取关联表的信息