我正在尝试使用ajax调用将参数从jsp传递到servlet。但是我没有通过参数。当我在servlet上打印它们时，它们只是null。我没有看到我在哪里犯错误。需要帮助
JSP：
<body>
<%
System.out.println("In Add-Edit Questions.jsp");
String Title=(String)request.getAttribute("Title");
System.out.println("Title:"+Title);
String Author=(String)request.getAttribute("Author");
System.out.println("Author:"+Author);
String currentq=(String)request.getAttribute("currentq").toString();
System.out.println("currentq:"+currentq);
if(currentq!=null){int curq=Integer.parseInt(currentq);}
int numq=0;
String noq=(String)request.getAttribute("noq").toString();
System.out.println("noq:"+noq);
if(noq!=null){numq=Integer.parseInt(noq);}
%>
<script type="text/javascript">
var T;
var A;
function populatereq()
{
T=document.getElementById("Title").value;
A=document.getElementById("Author").value;
}
function loadquestion(clicked)
{
populatereq();
var xmlhttp;
if (window.XMLHttpRequest)
{
xmlhttp=new XMLHttpRequest();
}
else
{
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
//document.getElementById("myDiv").innerHTML=xmlhttp.responseText;
//Populate fields;
var resT=xmlhttp.responseText;
alert(resT);
console.log(resT);
var array=resT.split("`");
document.getElementById("question").value=array[2];
document.getElementById("nq").value=array[3];
choice();
document.getElementById("desc").value=array[Number(array[3])+5];
document.getElementById("currentq").value=array[Number(array[3])+6];
for(k=1;k<Number(array[3]);k++)
{
document.getElementById("Choice"+k).value=array[3+k];
}
document.getElementById("A"+4+Number(array[3])).selected=true;
}
}
alert("Title="+T+"&Author="+A+"&loadq="+clicked);
xmlhttp.open("POST","Add_Edit_Questions",true);
xmlhttp.send("Title="+T+"&Author="+A+"&loadq="+clicked);
}
</script>
<div class="left-panel">
<b>Questions</b><br>
<form name="leftform" action="Add_Edit_Questions" method="get" id="add_edit_question_left">
<%for(int i=1;i<=numq;i++)
{%>
<br>
<a href="Add_Edit_Questions?Title=<%=Title %>&Author=<%=Author%>&loadq=<%=i %>"><button ><%="Question "+i %></button></a>
<br>
<%}%>
</form>
<a href="Add_Edit_Questions?Title=<%=Title %>&Author=<%=Author%>&loadq=new"><button>ADD</button></a>
</div>
<script type="text/javascript">
var number;
var i;
function choice()
{
var container=document.getElementById("choices");
while (container.hasChildNodes())
{
container.removeChild(container.lastChild);
}
number=document.getElementById("nq").value;
for (i=0;i<number;i++)
{
// Append a node with a random text
container.appendChild(document.createTextNode("Choice " + (i+1) +" : "));
// Create an <input> element, set its type and name attributes
var input = document.createElement("input");
input.type = "text";
input.name = "Choice" + (i+1);
input.id = "Choice" + (i+1);
input.required=true;
container.appendChild(input);
// Append a line break
container.appendChild(document.createElement("br"));
}
answerselect();
}
function answerselect()
{
var answerbox=document.getElementById("answer");
while (answerbox.hasChildNodes())
{
answerbox.removeChild(answerbox.lastChild);
}
answerbox.appendChild(document.createTextNode("Choose Answer : "));
var select = document.createElement("select");
select.name = "Answer";
for (i=0;i<number;i++)
{
var option = document.createElement("option");
option.id="A"+(i+1);
option.value=(i+1);
option.text = (i+1);
select.add(option,null);
}
answerbox.appendChild(select);
answerbox.appendChild(document.createElement("br"));
document.getElementById("descr").style.visibility="visible";
}
</script>
<div class="right-panel">
<b>Add/Edit Question</b><br>
<form name="myform" action="Add_Edit_Questions" method="get" id="add_edit_question">
<label>Question : </label><textarea rows="2" cols="50" name="question" form="add_edit_question"></textarea>
<!-- input type="text" name="question" id="question" placeholder="Enter your question here..." -->
<br>
<label>Select number of options : </label>
<select id="nq" onchange="choice()" name="nq">
<%for(int i=1;i<=10;i++){ %>
<option id=<%="O"+i %> value="<%=i %>"><%=i %> </option>
<%} %>
</select><br>
<div id="choices"></div>
<div id="answer"></div>
<div id="descr" style="visibility : hidden">
<label id="desclabel">Add Description : </label>
<textarea rows="5" cols="50" id="desc" name="desc" form="add_edit_question"></textarea>
</div>
<input type="hidden" name="attribute" id="atri"><!-- To tell whether to download QP or edit QP. -->
<input type="hidden" name="Title" id="Title" value=<%=Title %> >
<input type="hidden" name="Author" id="Author" value="<%=Author %>" >
<input type="hidden" name="currentq" id="currentq" value="<%=currentq %>">
<input type="submit" value="ADD TO QP" onclick="document.getElementById('atri').value='add2qp'">
<input type="submit" value="CREATE QP" onclick="document.getElementById('atri').value='download'">
</form>
</div>
</body>
问题仅出在AJAX上。
SERVLET：
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
System.out.println("In Add_Edit .java");
String Title=request.getParameter("Title");
System.out.println("title="+Title);//This is printing 'null' when ajax call is made
String Author=request.getParameter("Author");
System.out.println("author="+Author);//This is printing 'null' when ajax call is made
String loadq=request.getParameter("loadq");
System.out.println("loadq="+loadq);//This is printing 'null' when ajax call is made
/*
Here I will process request and write back required response text.
*/
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{
doGet(request,response);
}
}