Jessei
12/1/2016 - 10:00 AM
undefined null "" 's different
undefined null "" 's different
String a = request.getParameter("")//未获取到 为null
//判断 a == null
String a ;
//初始化后 a=""response.getParameter("")//未获取到 为undefinedundefined null "" 's different
String a = request.getParameter("")//未获取到 为null
//判断 a == null
String a ;
//初始化后 a=""response.getParameter("")//未获取到 为undefined