request.getParameter("username") == null "" :request.getParameter("username") 里的?和:怎么理解

request.getparameter(name) request.getAttribute() 和 request.getParameter() 有何区别? request.getAttribute() 和 request.getParameter() 有何区别? request.getParameter(username) == null :request.getParameter(username) 里的?和:怎么理解 请问这一句：userName = request.getParameter(userName + userId);在getParameter中是什么意思? session.getAttribute(request.getParameter解释一下JSP里面这个啥意思?Student stu = new Student();String id=request.getParameter(id);stu = (Student) session.getAttribute(request.getParameter(id));request.getParameter(id);返回个什么 关于request.getParameter()的问题for( j=1;j String userName=request.getParameter(userName);什么意思 jsp Cannot forward after response has been committed问题,String username = request.getParameter(username);String password = request.getParameter(password);String confirmPassword = request.getParameter(confirmPassword);String sql = select use 有没有知道这两句代码什么意思?本人比较着急!String dateStr=request.getParameter(year)+-+request.getParameter(month)+-+request.getParameter(day);Date date = java.sql.Date.valueOf(dateStr); JAVA中,如下面的代码,:这问号双引号冒号是什么表达式呀?怎么用?String bizorderid = request.getParameter(bizorderid)==null?:request.getParameter(bizorderid); jsp中request.getParameter(companyName);和request.getAttribute(cc)的区别是什么?在超链接里带的参数如何来接收? request.getParameter 和JAVA4大作用域的含义 小弟还未入门 request.getParameter()和request.getAttribute()的区别是什么?现在一直不太明白他们的区别到底是什么?request.getParameter()它得到请求参数的值,那值是从哪传递过来的? attribute和parameter的区别在网页设计中request.getParameter(),session.setAttribute(),session.getParameter().Parameter和attribute是如何区别的？ JSP中,String s2=new String(request.getParameter(s1).trim().getBytes(8859_1));%>这句话老出错这句话老出错,都不知道错在哪. while(s.hasMoreTokens())这句什么意思?//获取多行文本框中的信息String textarea=request.getParameter(textarea);//将信息按“ ”换行符进行分割StringTokenizer s=new StringTokenizer(textarea, );//判断是否还有分割 看见你的回答就知道高手 The left-hand side of an assignment must be a variable?dbString schoolingLength = request.getParameter(schooling_length);Double db = Double.parseDouble(schoolingLength);=1){}%>