学习必看：javacto.taobao.com
JSP文件
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript"
src="${pageContext.request.contextPath}/js/jquery-3.3.1.min.js"></script>
<script type="text/javascript">
function checkAAA(id) {
$.ajax({
type : "POST",
url : "${pageContext.request.contextPath}/servlet/BedServlet?method=findById",
data : "id=" + id,
success : function(data) {
var jsonStr = JSON.parse(data);
for ( var i in jsonStr) {
/* alert(jsonStr[i].id);
alert(jsonStr[i].name); */
$("#floor").append(
"<option value='"+jsonStr[i].id+"'>"
+ jsonStr[i].name + "</option>");
}
}
});
}
</script>
</head>
<body>
<form action="${pageContext.request.contextPath}/" method="post">
<table class="table table-condensed">
<tr class="form-group">
<td>所在大楼：</td>
<td><select class="form-control" onblur="checkAAA(this.value);">
<option value="1">天子楼</option>
<option value="2">黄鹤楼</option>
<option value="3">关西楼</option>
<option value="4">岳阳楼</option>
</select></td>
<td>所在楼层：</td>
<td><select name="floor" id="floor">
<!-- 动态生成二级菜单数据 -->
</select></td>
</tr>
</table>
</form>
</body>
</html>
JAVA代码：
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
PrintWriter out = resp.getWriter();
String methodName = req.getParameter("method");
String id = req.getParameter("id");
List<BedC> bedCs= new ArrayList<BedC>();// 此处应该通过id查询对应数据
BedC bedC1 = new BedC(1, "FL011");
BedC bedC2 = new BedC(2, "FL012");
BedC bedC3 = new BedC(3, "FL013");
BedC bedC4 = new BedC(4, "FL014");
BedC bedC5 = new BedC(5, "FL015");
bedCs.add(bedC1);
bedCs.add(bedC2);
bedCs.add(bedC3);
bedCs.add(bedC4);
bedCs.add(bedC5);
//把List集合数据转为JSON格式，需要包找我javacto.taobao.com
JSONArray listToJson = JSONArray.fromObject(bedCs);
out.print(listToJson);
}