为什么jsp request.getParameter（“ String”）在第一次调用后返回null？

Question

If I run my web project, in the first call I get the right Parameter (request.getParamter(userid)), but if I do more then one call, the request.getParamter Method always returns null.

I don't know why, and I have tried many things.

Thank you for your help.

in jsp I have this:

function addPersonToDatabase(userID){

var check = 0;
for (var zaehler = 0; zaehler < (document.getElementsByName("notinProject[]").length);   
 zaehler++) {

if (document.getElementsByName("notinProject[]")[zaehler].checked) {

location.href='<%=request.getContextPath()%>/administration/persons
action=addfrompersons&comingfrom=' + location.href + '&username=' + userID; 
        check++;
         }      
}


<form name='setcheckbox' id='setcheckbox' action='PersonControllerServlet' method='post' >

<input type="checkbox" name="notinProject[]" value="" onclick='javascript:addPersonToDatabase("
<%=lobjPerson.userName%)'><br> </td>

in servlet I have this:

String lstrUserName=request.getParameter("username");

Answer 1

尝试：

onclick='javascript:addPersonToDatabase("<%=lobjPerson.userName%>")'>