在 jsp/servlet 中将调查数据插入 mySql 数据库
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【中文标题】在 jsp/servlet 中将调查数据插入 mySql 数据库【英文标题】：Inserting survey data to mySql database in jsp/servlet 【发布时间】：2020-07-03 10:08:06 【问题描述】：我已创建调查表并尝试在数据库中一次插入多个问题，但显示空指针错误。我已动态创建该字段
jsp 文件：在这里，我在单击显示 priview 按钮时创建调查问题，它被添加到预览 div。通过此我创建多个问题，然后通过单击保存按钮提交到数据库
<form method="post" action="getSurvey">
<div id="section1">
<div>
<label for="surveyName" class="labelstyle">Enter Survey Title</label>
<input type="text" id="surveyName" name="surveyName[]" >
</div>
<br>
<div>
<label for="surveyQuestion" class="labelstyle" >Enter Question </label>
<input type="text" id="surveyQuestion" name="surveyQuestion[]" >
<select name="answerType" id="answerType" class="selectPicker" >
<option selected="selected">None</option>
<option value="multiple">Multiple Choice type</option>
<option value="single">Single Choice Type</option>
<option value="short">Short Answer Type</option>
</select>
</div>
<div id="newSurvey">
</div>
<div>
<button type="button" id="showPreview" name="showPreview" class="button">Show Preview</button>
</div>
</div>
<div id="section2">
<div>
<input type="submit" name="saveSurvey" id="saveSurvey" value="Save" class="button" >
</div>
<h2 class="heading1">Preview</h2>
<div id="preview">
</div>
</div>
</form>
jquery: to generate fields dynamically
$(document).ready(function()
var questionCounter=1;
const $previewid = $('#preview');
$("select.selectPicker").change(function()
var option = $(this).children("option:selected").val();
if(option=="multiple")
$.fn.callMultiple();
else if(option=="single")
$.fn.callSingle();
else if(option=="short")
$.fn.callShort();
else
alert("Please select from options");
);
$.fn.callMultiple = function()
$('#newSurvey').empty();
var selectType = $('#answerType').val();
let newrow='<input type="checkbox" name="check1"><input type="text" id="t1" name="txt1[]"><br>'+
'<input type="checkbox" name="check2"><input type="text" id="t2" name="txt2[]"><br>'+
'<input type="checkbox" name="check3"><input type="text" id="t3" name="txt3[]"><br>'+
'<input type="checkbox" name="check4"><input type="text" id="t4" name="txt4[]"><br>';+
'<input type="hidden" name="stype[]" id="stype" value="'+selectType+'">';
$('#newSurvey').append(newrow);
$.fn.callSingle = function()
$('#newSurvey').empty();
var selectType = $('#answerType').val();
let newrow='<input type="radio" name="radioval"><input type="text" id="t1" name="txt1[]"><br>'+
'<input type="radio" name="radioval"><input type="text" id="t2" name="txt2[]"><br>'+
'<input type="radio" name="radioval"><input type="text" id="t3" name="txt3[]"><br>'+
'<input type="radio" name="radioval"><input type="text" id="t4" name="txt4[]"><br>';+
'<input type="hidden" name="stype[]" id="stype" value="'+selectType+'">';
$('#newSurvey').append(newrow);
$.fn.callShort = function()
$('#newSurvey').empty();
var selectType = $('#answerType').val();
let newrow='<input type="text" name="shortanswer[]" id="shortanswer">';+
'<input type="hidden" name="stype[]" id="stype" value="'+selectType+'">';
$('#newSurvey').append(newrow);
$('#showPreview').on('click',function(e)
questionCounter++;
var title = $('#surveyName').val();
var question = $('#surveyQuestion').val();
var uprow='<br><center><input type="text" id="surveyName" name="surveyName[]" value='+title+' readonly></center><br>'+
' <input type="text" id="surveyQuestion" name="surveyQuestion[]" value='+question+' readonly><br><br>';
const $firstRow = $('#newSurvey').find("*");
let $newrowhtml = $firstRow.clone(true);
$('#section1').find(":input").val("");
$previewid.prepend($newrowhtml);
$previewid.prepend(uprow);
$previewid.find(":input").attr('readonly','readonly');
);
);
servlet 我正在尝试将属于预览 div 一部分的数据保存在 jsp 文件中
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
PrintWriter out = response.getWriter();
String surveyTitle[] = request.getParameterValues("surveyName[]");
String question[] = request.getParameterValues("surveyQuestion[]");
String[] option1, option2, option3, option4, single;
int row1=0,row2=0;
int i;
option1=option2=option3=option4=single=null;
option1=request.getParameterValues("txt1[]");
option2=request.getParameterValues("txt2[]");
option3=request.getParameterValues("txt3[]");
option4=request.getParameterValues("txt4[]");
String selectType[]=request.getParameterValues("stype[]");
out.println(selectType.length);
for( i=0;i<selectType.length;i++)
out.println(selectType[i]+" "+i);
if(request.getParameterValues("shortanswer[]") != null)
single=request.getParameterValues("shortanswer[]");
for( i=0;i<single.length;i++)
out.println(single[i]+" "+i);
String[] op1,op2,op3,op4,ans;
op1=op2=op3=op4=ans=null;
int k=0,j=0;
for(i=1;i<surveyTitle.length;i++)
if((selectType[i].equals("multiple"))||selectType[i].equals("single"))
op1[i]=option1[j];
op2[i]=option2[j];
op3[i]=option3[j];
op4[i]=option4[j];
ans[i]=null;
j++;
else if(selectType.equals("short"))
op1[i]=null;
op2[i]=null;
op3[i]=null;
op4[i]=null;
ans[i]=single[k];
k++;
out.println(op1[i]+""+op2[i]+""+op3[i]+""+op4[i]+""+ans[i]);
try
Class.forName(JDBC_Driver);
con = DriverManager.getConnection(URL, username, password);
for(i=1;i<surveyTitle.length;i++)
if((selectType[i].equals("multiple"))||selectType[i].equals("single"))
query1 ="insert into surveydetail (surveyTitle,questionName,optionOne,optionTwo,optionThree,optionFour,selectType) values (?,?,?,?,?,?,?)";
pstmt1 = con.prepareStatement(query1);
pstmt1.clearParameters();
pstmt1.setString(1, surveyTitle[i]);
pstmt1.setString(2, question[i]);
pstmt1.setString(3, op1[i]);
pstmt1.setString(4, op2[i]);
pstmt1.setString(5, op3[i]);
pstmt1.setString(6, op4[i]);
pstmt1.setString(7, selectType[i]);
row1=pstmt1.executeUpdate();
else if(selectType.equals("short"))
query2 ="insert into surveydetail (surveyTitle,questionName,shortAnswer,selectType) values (?,?,?,?)";
pstmt2 = con.prepareStatement(query2);
pstmt2.clearParameters();
pstmt2.setString(1, surveyTitle[i]);
pstmt2.setString(2, question[i]);
pstmt2.setString(3, ans[i]);
pstmt2.setString(4, selectType[i]);
row2=pstmt1.executeUpdate();
if((row1>0)||(row2>0))
response.sendRedirect("CreateSurveyView.jsp");
else
response.sendRedirect("Error.jsp");
catch (Exception e)
// TODO Auto-generated catch block
e.printStackTrace();
【问题讨论】：
它在哪里给你 null ？ 在文本字段 txt 中，也不显示选择类型的值 在调试时，我正在获取除名称为 txt 的文本字段之外的所有元素的值，然后选择下拉列表。我不知道我在哪里犯错 因为在预览时您没有获得特定问题的选择值。当您单击预览时添加一些隐藏字段，以便选择类型也将与该问题一起添加 我添加了隐藏字段，但仍然没有显示任何值 【参考方案1】：在您的 jsp 代码中，您没有添加任何 inputs 来识别选择类型是单、短还是多。现在添加，当用户从下拉列表中选择任何选项时，您只需附加一个 @987654322 @ 输入 radios 或 checkboxes。
您需要在 jsp 和 jquery 中进行一些更改：
<div id="section1">
<!--other fields-->
</div>
<!--add form tag here-->
<form method="post" action="getSurvey">
<div id="section2">
<div>
<input type="submit" name="saveSurvey" id="saveSurvey" value="Save" class="button" >
</div>
<h2 class="heading1">Preview</h2>
<div id="preview">
</div>
</div>
</form>
Jquery 代码：
$(document).ready(function()
var questionCounter = 1;
$("select.selectPicker").change(function()
//your codes
);
$.fn.callMultiple = function()
$('#newSurvey').empty();
//added hidden input with name="answerType1[]"
var newrow = '<input type="hidden" name="answerType1[]" value="multiple"/>' +
'<input type="checkbox" name="check1"><input type="text" id="t1_" name="txt1[]"><br>' +
'<input type="checkbox" name="check2"><input type="text" id="t2" name="txt2[]"><br>' +
'<input type="checkbox" name="check3"><input type="text" id="t3" name="txt3[]"><br>' +
'<input type="checkbox" name="check4"><input type="text" id="t4" name="txt4[]"><br>';
$('#newSurvey').append(newrow);
$.fn.callSingle = function()
$('#newSurvey').empty();
//added hidden input with name="answerType1[]"
var newrow = '<input type="hidden" name="answerType1[]" value="single"/>' +
'<input type="radio" name="radioval"><input type="text" id="t1" name="txt1[]"><br>' +
'<input type="radio" name="radioval"><input type="text" id="t2" name="txt2[]"><br>' +
'<input type="radio" name="radioval"><input type="text" id="t3" name="txt3[]"><br>' +
'<input type="radio" name="radioval"><input type="text" id="t4" name="txt4[]"><br>';
$('#newSurvey').append(newrow);
$.fn.callShort = function()
$('#newSurvey').empty();
//added hidden input with name="answerType1[]"
var newrow = '<input type="hidden" name="answerType1[]" value="short"/>' + '<input type="text" name="txt[]" id="t1">';
$('#newSurvey').append(newrow);
//other codes
);
现在，在您的 servlet 代码中进行以下更改：
String surveyTitle[] = request.getParameterValues("surveyName[]");
String question[] = request.getParameterValues("surveyQuestion[]");
String[] option1, option2, option3, option4, answer;
int row1 = 0, row2 = 0;
int i;
PreparedStatement pstmt1, pstmt2;
option1 = option2 = option3 = option4 = answer = null;
//if txt1[] not null get values
if (request.getParameterValues("txt1[]") != null)
option1 = request.getParameterValues("txt1[]");
option2 = request.getParameterValues("txt2[]");
option3 = request.getParameterValues("txt3[]");
option4 = request.getParameterValues("txt4[]");
//if txt[] "short ans" is not null get value
if (request.getParameterValues("txt[]") != null)
answer = request.getParameterValues("txt[]");
//get select type
String selectType[] = request.getParameterValues("answerType1[]");
//for answer
int j = 0;
try
Class.forName(JDBC_Driver);
con = DriverManager.getConnection(URL, username, password);
out.println(question.length); //seeing length of question
//looping through question array
for (i = 0; i < question.length; i++)
//chcking the selecttype
if ((selectType[i].equals("multiple")) || (selectType[i].equals("single")))
//insert
String query1 = "insert into surveydetail (surveyTitle,questionName,optionOne,optionTwo,optionThree,optionFour,selectType) values (?,?,?,?,?,?,?)";
pstmt1 = con.prepareStatement(query1);
pstmt1.clearParameters();
pstmt1.setString(1, surveyTitle[i]);
pstmt1.setString(2, question[i]);
pstmt1.setString(3, option1[i]);
pstmt1.setString(4, option2[i]);
pstmt1.setString(5, option3[i]);
pstmt1.setString(6, option4[i]);
pstmt1.setString(7, selectType[i]);
out.println(" " + surveyTitle[i] + " " + question[i] + " " + option1[i] + " " + option2[i] + " " + option3[i] + " " + option4[i] + " " + selectType[i]);
row1 = pstmt1.executeUpdate();
else if (selectType[i].equals("short"))
//insert
String query2 = "insert into surveydetail (surveyTitle,questionName,shortAnswer,selectType) values (?,?,?,?)";
pstmt2 = con.prepareStatement(query2);
pstmt2.clearParameters();
pstmt2.setString(1, surveyTitle[i]);
pstmt2.setString(2, question[i]);
pstmt2.setString(3, answer[j]);//here we will pass "j" value
pstmt2.setString(4, selectType[i]);
row2 = pstmt2.executeUpdate();
out.println(" " + surveyTitle[i] + " " + question[i] + " " + answer[j] + " " + selectType[i]);
j++;
if ((row1 > 0) || (row2 > 0))
response.sendRedirect("CreateSurveyView.jsp");
else
response.sendRedirect("Error.jsp");
catch (Exception e)
// TODO Auto-generated catch block
e.printStackTrace();
（上面的代码已经用数据库测试过并且工作正常）
【讨论】：
感谢 swati 我已经做到了，但感谢...寻求帮助以上是关于在 jsp/servlet 中将调查数据插入 mySql 数据库的主要内容，如果未能解决你的问题，请参考以下文章
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